ABUNDANT PLANKTIC FORAMINIFERA IN INTERTIDAL SEDIMENTS, KAWERUA, NORTHLAND

By Bruce W. Hay ward New Zealand Geological Survey, P .O. Box 30 368, Lower H u t t

S U M M A R Y

Planktics comprise 3-40% (average 21%) of the foraminiferal faunas in intertidal and shallow subtidal (0-2.5m) sediments along the rocky and ocean beach coastline of Kawerua on the west coast of Northland, New Zealand. This extraordinarily high relative abundance is argued to be a result of dominant onshore winds and seas in the area, which carry planktic tests in the surface waters shore wards.

These faunas, and those of the adjacent shelf and slope (down to 1300m) are dominated by Globigerina falconensis, G. quinqueloba and Globorotalia inflata. The shoreline faunas differ however in their greater relative abundance of Globigerina bulloides, Globigerinoides ruber, Orbulina universa and Globigerinella aequilateralis. This may result from the greater buoyancy of their large, spinose tests, their greater productivity in particular years and the greater loss of more fragile, smaller species in the mobile, nearshore sediments. Variations in the relative abundance of different taxa and in the total planktic percentage between these shoreline samples, may result from different exposures to abrasion, winnowing, and longshore currents, and locally different rates of benthic foraminiferal production.

A total of 22 species are recorded from the Kawerua shoreline and adjacent shelf and slope. These include the northernmost New Zealand record of Globorotalia cavernula and the first records of Globigerinella calida and Globorotalia bermudezi from the New Zealand area.

INTRODUCTION

Foraminifera are microscopic, marine protozoa that secrete or build a chambered test (shell) of calcite, aragonite or sand grains. Despite their size, planktic foraminifera are important members of the open ocean plankton. Their importance stems from their immense productivity, world-wide distribution and their calcite tests, which constantly 'rain' down on the sea bed where they have accumulated in great abundance over the past 130 million years. Thus, Cretaceous and Cenozoic marine sedimentary rocks, that occur today uplifted on land as well as beneath the oceans, contain vast numbers of planktic foraminiferal tests. These are of major significance in investigations of global biostratigraphy, paleoclimatology, paleo-oceanography, paleogeography and plate tecto-

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nics. These studies all require a background knowledge of the biology and distribution of modern planktic foraminifera and their tests. This paper addresses this latter aspect in an area adjacent to the Auckland University Field Club's Research Station at Kawerua on the west coast of Northland, New Zealand (Fig. 1).

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Fig. 1. Sample location maps. a. Map of New Zealand showing approximate distribution of foraminiferal provinces and surface currents; b. Map of Northland showing location of four offshore stations; c. and d. Maps of the Kawerua coastline showing location of intertidal and shallow subtidal stations.

In the New Zealand region there have been 2 studies primarily on the distribution of modern planktic foraminifera. Kustanowich (1963) looked at specimens from 20 sediment samples taken between 19°S and 55°S and Eade (1973) worked on material collected in 28 plankton tows between 18°S and 36°S. Hayward (1983) updated their taxonomy in the light of major overseas revisions, and presented an illustrated review of all taxa occurring in New Zealand waters, and their broad distribution. A similar study to the present one was made on the planktic foraminifera of inner shelf sediments around the Cavalli Islands, east coast of Northland by Hayward (1979a). Previous records of planktic forami­nifera in the present study area around Kawerua have been included in Hedley et al (1965) and Hayward (1979b). Hedley et al (1965) recorded 5 species and Hayward (1979b) 12 species.

S A M P L E S (Appendix I, Fig. 1)

Sediment samples from 17 stations were selected for study. Thirteen stations are from intertidal or shallow subtidal locations along the Kawerua coast and four stations are between 50 and 1300m depth off the west coast of Northland. Stations 1 - 4 were collected in January 1979 from an intertidal Zostera pool and reported on by Hayward (1979b). Stations 5 -13 were collected in June 1981 from the Kawerua coastline. Stations 14 and 15 were collected in 1932 by RRS Discovery II from 57m and 87m depths (Discovery stations D937 and D939). Stations 16 and 17 were collected in the early 1960's by New Zealand Oceanographic Institute from 400m and 1300m. Samples from these last four stations were obtained from New Zealand Geological Survey, Micropaleontology Section store.

A l l samples were thoroughly washed over a 200 mesh sieve and the foraminifera concentrated by floating with carbon tetrachloride. A bulk pick of 100 foraminifera (benthic plus planktic) was made from a split of the floated material to give a crude estimate of the percentage of planktics in the foraminiferal fauna. Where sufficient specimens were available, further splits were picked until 100 planktics had been obtained to give estimates of the relative abundance of each taxon. In several samples rich in planktics, further material was examined to obtain specimens of any additional rare taxa not represented in the 100 count (Appendix II).

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R E L A T I V E A B U N D A N C E OF P L A N K T I C FORAMINIFERA

The percentage of planktics in a fossil foraminiferal fauna is often used by paleontologists as a general guide to the distance from shore and as a consequence also the depth at the time of accumulation (Vella 1962). This results from the fact that the majority of planktic foraminifera live in the upper few hundred metres of the clear, oceanic waters and their numbers and diversity rapidly drop off in the dirtier, neritic waters that surround most lands (Boltovskoy and Wright 1976).

In this study the four offshore stations (14 - 17) show the normal increase in planktics with increasing distance from shore and depth (Appendix I). Their percentages are about normal to a little low on the average expected around New Zealand (Table 1).

Table 1. Comparison of planktic foraminiferal percentage in samples around Kawerua with average values for New Zealand cited by Vella (1962).

Kawerua: Depth Intertidal 57 m 87 m 400 m 1300 m Planktic % 3-40% 12% 16% 45% 75%

Vella (1962): Planktic % 0% 10% 10-50% 50-75% 75-100% Depth 0-20 m 20-70 m 70-130 m 130-1000 m 1000 m+

The planktic percentage in the intertidal and shallow subtidal stations (1-13) along the Kawerua coast ranges between 3 and 40%, averaging 21%. These values are extraordinarily high and unusually variable for such an environment (Table 1), and if found in a fossil sample and used without reference to the accompanying benthics, would result in depth estimates of between 5 and 150m. Vella (1962) did note however that planktic foraminiferal shells occasionally accumulate abundantly near shore where on-shore winds may periodically blow oceanic water masses towards the shore. This no doubt is the explanation for the high values obtained here, for the west coast of northern New Zealand is notorious for its rough seas, large swells, and westerly winds.

It might be argued that these are unusual situations. Most of the samples were collected among rocky reefs and tidal pools, and these may preferentially trap and concentrate suspended planktic foraminiferal tests more than bottom transported benthics. This may be partly so, but planktic percentages of 20-33% from the ocean beach (stations 11-13) are not explained by it.

The great variation in planktic percentages between nearby intertidal samples is difficult to account for. For example, station 7 (3% planktics) and station 10 (40%) are 400 m apart and both located in low tide sand at the head of narrow gaps between reefs. Since all the stations

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(1-4, 7-9) with the lower planktic percentages (less than 20%) are clustered together just north of Kawerua Point, the explanation may have something to do with local long-shore drift and currents sweeping the planktic tests past this area. It is also possible that the local production of benthic foraminifera is greater in this area, thereby reducing the relative abundance of planktics in the faunas.

TAXONOMIC COMPOSITION (Fig. 2, Appendix II)

The common planktic foraminifera in the four offshore samples are Globigerina falconensis, G. quinqueloba and Globorotalia inflata. With increasing distance from shore and increasing depth, the abundance of G. falconensis decreases dramatically whereas the abundance of G. inflata, Neogloboquadrina pachyderma, Globigerinita glutinata and total Globorotalia species increases. The percentage of G. quinqueloba is variable, with a peak of 57% abundance at 400m. These trends are largely related to the preferred depths at which different species live in the water column. Species of Globigerina, Globigerinoides, Globigerinella and Orbulina live predominantly in the upper 100m of water and feed on phytoplankton, whereas N. pachyderma and species of Globorotalia live as juveniles in the upper few 100 metres and as adults in water deeper than 100m and are omnivores (Be 1977).

In the intertidal and shallow subtidal samples at Kawerua, the dominant species are G. falconensis, G. quinqueloba, G. bulloides, Globigerinoides ruber, G. inflata and Orbulina universa. These faunas are almost exclusively composed of species that live in the upper 100m of the water column or the shallow-living juveniles of deep water taxa. The overall composition of the Kawerua shoreline fauna is significantly different from that of offshore samples, even those at 57m and 87m depth, primarily in the greater abundance of G. bulloides, G. ruber, O. universa and Globigerinella aequilateralis. There are a number of possible explanations:

1. It is possible that the offshore samples, taken by dredge, contain an averaged planktic fauna for a long time period (e.g. 10s to 100s of years), whereas the shoreline samples, taken by hand from the upper 2cm of highly mobile sediment, may represent the planktic fauna for the last few months or years. This could be especially true on the exposed ocean beach (stations 11-13) where continual movement of coarse sand would quickly abrade away the tests, and on the rocky intertidal shelves (stations 5, 6) where the thin veneer of fine sediment may be swept away periodically by storms to allow accumulation of new deposits.

Berger (1971) has shown that large (up to ten-fold), long term (1-20

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2. Planktic foraminifera from sediments along the Kawerua coast and adjacent shelf and slope. a. Globigerina bulloides (FP 3535). b. Globigerina falconensis (FP 3536), c. Globigerina quinqueloba (FP3537), d. Globigerinella aequilateralis (FP 3538), e. Globigerinella calida (FP 3539), f. Globigerinoides ruber (FP 3540), g-i. Globorotalia bermudezi (FP 3541-43), j . Globorotalia cavernula (FP 3544), k. Globorotalia inflata (FP 3545), 1. Orbulina universa (FP 3546). Bar scale = 0.1mm.

years) variations in the production of foraminiferal tests occur, both in total production and in the relative abundance of species. The species Berger found to have large variations were G. bulloides, O. universa, G. ruber and G. aequilateralis — the four taxa having much greater relative abundance in the shoreline samples than offshore in the present study. Maybe the late 1970's and early 1980's was a period of relatively high production of these tests in the waters off western Northland. Differences in the post-mortem buoyancy of tests could also be significant. The more buoyant tests would stay in the surface waters longer and be concentrated there as they were carried shoreward. Berger and Piper (1972) showed that the tests of spinose taxa (e.g. Globigerina, Globigerinoides, Globigerinella, Orbulina) sink more slowly than those of non-spinose taxa (e.g. Globoratalia, Neogloboquadrina, Globigerinita). The Kawerua shore samples contain 85-95% spinose taxa, which is the same as that found at 57m depth (87%) offshore but greater than that at 87m (63%), 400m (76%) and 1300m (49%). G. ruber has a particularly spinose test and seems to retain its spines longer after death than most other taxa, and this may explain its unusually high relative abundance onshore.

The large, thin-walled tests of O. universa and G. bulloides may also be more buoyant than those of many other thicker walled encrusted taxa, as they are often found in shallow sediments, even on the sheltered east coast and in harbours. Test abrasion may be a significant contributing factor, as it would result in the more rapid loss of smaller tests (e.g. G. falconensis, G. quinqueloba) relative to the larger ones, in the mobile, nearshore and intertidal sediments. Possibly one of the most significant reasons for the difference between the shoreline and offshore faunas, relates to the depth at which different taxa live in the water column, and the probability that the surface waters are the main part being swept shoreward carrying mostly shallow-living taxa with them. This would explain the increased abundance of G. bulloides, G. ruber, O. universa and Globigerinella aequilateralis (all shallow-living) in the shoreline samples, but does not explain why another shallow-living species (Globigerina quinqueloba) is usually found in greater numbers in

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offshore samples. This may be explained by winnowing of th» shoreline samples and removal of most of the small species (e.g Globigerina quinqueloba).

Abrasion, together with current and wave winnowing of these nearshore sediments, probably accounts for most of the wide variation in the faunal composition within the Kawerua coast samples. The clean well-sorted, coarse sands (e.g. stations 4, 9-13) contain a far greater percentage of tests of the larger taxa (e.g. G. bulloides, G. ruber, O universa) than do the fine and medium sands (e.g. stations 3, 5-8), which are dominated by the smaller tests of G. quinqueloba and G. falconensis.

BIOGEOGRAPHY

In the world's oceans and in ocean bottom sediments, planktic foraminifera exhibit a zonation in roughly parallel latitudinal belts that are duplicated on either side of the equator. This has enabled workers to recognise five worldwide provinces — Tropical, Subtropical, Transition­al, Subpolar and Polar (Be and Tolderlund 1971, Be 1977). Previous work summarised by Hayward (1983) indicates that most of New Zealand straddles the Transitional Province grading into the cooler part of the Subtropical Province in the vicinity of Northland.

The fauna around Kawerua and the west coast of Northland is typical of the Transitional Province with abundant G. inflata and a mixture of forms characteristic of cool water (G. bulloides, G. quinqueloba, N. pachyderma) and warm water (G. ruber, Globorotalia crassula). Among the rare taxa there is also a mixture of cool water (Globigerinita bradyi, Globorotalia cavernula, G. hirsuta) and warm water (Pulleniatina obliquiloculata, Globigerinoides sacculifer, Neogloboquadrina dutertrei) forms. A diversity of 22 species of planktic foraminifera off the west coast of Northland (Appendix II) is high and represents about 60% of the species presently living in the world oceans. This high diversity is a reflection of the location near the boundary between the Subtropical and Transitional Province.

The record of G. cavernula (Fig. 2j) from station 17 is the north­ernmost record (latitude 36°S) of this species in New Zealand waters.

N E W RECORDS F R O M NEW Z E A L A N D WATERS

Two species, not recognised or illustrated by Hayward (1983), nor previously recorded from New Zealand waters, have been found in the present samples.

Globigerinella calida (Parker) Fig. 2e

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L962 Globigerina calida Parker, p. 221, pi. 1, figs. 9-13, 15. This species is characterised by having an aperture extending from

the umbilicus to the periphery; by its ovate chambers, and lobulate outline. It is usually found in the Tropical and Subtropical Provinces.

In this study, it has been recognised in small numbers in stations 10 and 17 (low tide and 1300m).

Globorotalia bermudezi (Rogl and Bolli) Fig 2g-i 1973 Globorotalia bermudezi Rogl and Bolli, p. 567, pi. 6, figs. 16-20; pi. 16, figs. 1-3.

This species is similar to Globorotalia scitula, being distinguished by its smaller size, more numerous chambers per whorl, more inflated chambers on the involute side, and more irregularly perforated test.

In this study it has been recognised in stations 15, 16 and 17 (87m, 400m and 1300m). It has also recently been recognised in samples from off Great Barrier Island.

DISCUSSION

From other unpublished observations and from the studies in Manukau Harbour (Hulme 1964), it would appear that unusually high abundances of planktic foraminifera in intertidal and harbour locations are typical rather than abnormal for the west coast of northern New Zealand. They are in strong contrast to the more usual low percentages (fewer than 10%) occurring in intertidal and inner shelf sediments (0-40m) on the more sheltered east coast of northern New Zealand (Hayward 1979b, 1981, Hayward and Grace 1981, Hayward et al 1984).

Taxonomically the fauna on the inner shelf of the east coast is very similar to that found on the west coast at 57m and 87m in this study. Both are dominated by G. falconensis, G. quinqueloba and G. inflata with low abundances of many other taxa. The fauna on the east side appears to have a slightly higher relative abundance of warm water taxa (G. crassula, N. dutertrei, G. sacculifer) and the west side has a slightly higher abundance of cool water taxa (G. quinqueloba, G. bulloides, N. pachyderma). This is probably a result of the warm East Auckland Current that flows south down the east side of northern New Zealand (Fig. 1).

A C K N O W L E D G E M E N T S

I thank Fred Brook and Hugh Grenfell for company in the field while collecting from stations 5-13 in 1981. Fred braved the chilling waters to collect station 8. Scanning electron microscope photographs are the work of Barry Burt.

The text has benefitted from the critical reviews of George Scott and Bob Hoskins.

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R E F E R E N C E S

Be, A.W.H. 1977: A n ecological, zoogeographic and taxonomic review of Recent planktonic foraminifera. pp. 1-100 in Ramsay, A.T.S. (ed) 'Oceanic Micropaleonotology' Academit Press, London.

Be, A .W.H. & Tolderlund, D.S. 1971: Distribution and ecology of living planktonic foraminifera in surface waters of the Atlantic and Indian Oceans, pp. 105-149 in. Funnel, B .M. and Riedel, W.R. (eds) 'Micropaleontology of Oceans' Cambridge University Press, London.

Berger, W.H. 1971: Sedimentation of planktonic foraminifera: Marine Geology 22: 325-358.

Berger, W.H. & Piper, D.J.W. 1972: Planktonic foraminifera: Differential settling, dissolution and redeposition. Limnology and Oceanography 17: 275-287.

Boltovskoy, E. & Wright, R. 1976: 'Recent foraminifera'. W. Junk, The Hague, 515p. Eade, J .V . 1973: Geographical distribution of living Planktic foraminifera in the

south-west Pacific, pp. 249-256 in Fraser, R. (comp.) 'Oceanography of the South Pacific 1972'. N.Z. National Commission for UNESCO, Wellington.

Hayward, B.W. 1979a: Planktic foraminifera in surface sediments around the Cavalli Islands, northern New Zealand. Tane 25:149-155.

Hayward, B.W. 1979b: An intertidal Zostera pool community at Kawerua, Northland, and its foraminiferal microfauna. Tane 25: 173-186.

Hayward, B.W. 1981: Foraminifera in nearshore sediments of the eastern Bay of Islands, northern New Zealand. Tane 27: 123-134.

Hayward, B.W. 1983: Planktic foraminifera (Protozoa) in New Zealand waters: a taxonomic review. New Zealand Journal of Zoology 10: 63-74.

Hayward, B.W. & Grace, R.V. 1981: Soft-bottom macrofauna and foraminiferal micro-fauna off Cuvier Island, northeast New Zealand. Tane 27: 43-54.

Hayward, B.W., Grace, R.V. & Bull , V . H . 1984: Soft bottom macrofauna, foraminifera and sediments off the Chickens Island, northern New Zealand Tane 30: 141-164.

Hedley, R.H. , Hurdle, C M . & Burdett, I.D.J. 1965: 'A foraminiferal fauna from the western continental shelf, North Island, New Zealand'. New Zealand Oceanographic Memoir No. 25, 47p.

Hulme, S.G. 1964: Recent foraminifera from the Manukau Harbour, Auckland, New Zealand. New Zealand Journal of Science 7: 305-340.

Kustanowich, S. 1963: Distribution of planktonic foraminifera in surface sediments of the south-west Pacific Ocean. New Zealand Journal of Geology and Geophysics 6: 534-565.

Parker, F.L. 1962: Planktonic foraminiferal species in Pacific sediments. Micropalentology 8: 219-254.

Rogl, F. & Bolli, H . M . 1973: Holocene to Pleistocene planktonic foraminifera of Leg 15, site 147 (Cariaco Basin (Trench) Caribean Sea) and their climatic significance, pp. 553-616 in Edgar, N.T. (ed.) 'Initial Reports of the Deep Sea Drilling Project, v. 15' U.S. Government Printing Office, Washington D.C.

Vella, P. 1962: Determining depths of New Zealand Tertiary seas. A n introduction to depth paleoecology. Tuatara 10: 19-40.

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APPENDIX I. Station Data.

Station Depth* % Planktics Sediment NZGS Cat. No. 1 MT 14 Corallina turf F201680 2 MT 17 muddy sand F201681 3 MT 13 medium sand F201682 4 MT ? sandy gravel F201683 5 MT 32 fine sand F201900 6 MT 29 medium sand F201899 7 LT 3 fine sand F201898 8 2.5m 6 fine sand F201895 9 LT 16 gravelly sand F201896 10 LT 40 coarse sand F201897 11 HT 22 coarse sand F201901 12 HT 33 coarse sand F201902 13 HT 25 coarse sand F201903 14 57m 12 F201304 15 87m 16 F201009 16 400m 45 F201392 17 1300m 75 F201397

* HT = high tide level, MT = mid tide level, LT = low tide level

APPENDIX II. Planktic foraminifera from the Kawerua coast and offshore. Arabic numerals = percentage of planktic foraminiferal fauna; X = present.

A B C D E F G H I J Globigerina bulloides d'Orbigny 21 7 15 28 - 20 3 X 1 4 Globigerina falconensis Blow 21 36 26 23 X 25 49 32 13 13 Globigerina humilis (Brady) 1 2 Globigerina quinqueloba Natland 17 40 7 18 X 21 34 25 57 24 Globigerinella aequilateralis (Brady) 5 3 X 4 X 4 X 4 2 X Globigerinella calida (Parker) - - - 1 - X - - - X Globigerinita bradyi (Wiesner) 1 - - - X Globigerinita glutinata (Egger) 1 - 4 - - 1 1 6 10 11 Globigerinita iota Parker 1 2 Globigerinoides ruber (d'Orbigny) 11 6 22 17 X 1 2 - 1 X 3 Globigerinoides sacculifer (Brady) - - X - - X - 1 1 X Globorotalia bermudezi Rogl and Bolli X X I Globorotalia cavernula Be X Globorotalia crassula Cushman and Stewart - 1 - - - X - 2 1 3 Globorotalia hirsuta (d'Orbigny) - - X - - X 1 X X 1 Globorotalia inflata (d'Orbigny) 11 3 11 4 X 8 9 22 6 21 Globorotalia scitula (Brady) X X I Globorotalia truncatulinoides (d'Orbigny) 2 1 X X - 1 X 1 1 1 Neogloboquadrina dutertrei (d'Orbigny) - - X X - X - - 1 3 Neogloboquadrina pachyderma (Ehrenberg) - 1 - 3 - 1 2 6 4 7 Orbulina universa d'Orbigny 11 1 1 5 2 - 7 I X 1 3 Pulleniatina obliquiloculata (Parker and Jones) X - - - - X - - X X

Samples: A = Kawerua stations 1-4 combined B = Kawerua stations 5-7 combined C = Kawerua stations 8-9 combined D = Kawerua station 10 E = Kawerua stations 11-13 combined

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F = Kawerua stations 1-13 combined G = offshore station 14, 57m H = offshore station 15, 87m I = offshore station 16, 400m J = offshore station 17, 1300m

PARYPHANTA AT PAWAKATUTU

by A.P. Ballance c/- 7 Florida Place, Auckland 5.

ABSTRACT

During a 2 day collection in a stand of 26 year old pines in the Waipoua Forest, Northland, 18 live Paryphanta busbyi busbyi (Gray 1840) and 67 shells and shell fragments were recovered. The live snails were measured, tagged and released.

INTRODUCTION

Work on a population of kauri snails, Paryphanta busbyi busbyi, at Pawakatutu near Kawerua, was carried out during the Auckland University Field Club's scientific trip to its research station at Kawerua in July 1983. Kawerua is on the west coast of Northland, 17 kilometres south of the Hokianga Harbour. Pawakatutu is approximately 4 kilometres north east of Kawerua, between the Wairau River and the Ohae Stream (Fig. 1). The study area is approximately two hectares in size and adjacent to a derelict house.

It is planted in Pinus elliotti, and surrounded by manuka scrub. This study area was chosen because it had a known and easily accessible population of Paryphanta, there was little undergrowth, and hence it was relatively easy to search.

This study was carried out to provide information on the numbers of live and dead Paryphanta in a small well defined area, and to act as a baseline study for future work in the same locality. By measuring tagged individuals over a few years I hope to establish growth rates, longevity and the relationship between age and size.

METHODS

The area of the pines was sampled intensively for Paryphanta on two successive days by three people. We concentrated the search effort in leaf and pine needle litter mounds at the base of pine trees and occasional small native shrubs. The location of each live snail, dead shell and shell fragment was mapped by its location in relation to pine trees which were numbered and marked with orange spray paint as the study progressed. We numbered each live snail using white nail polish, and released them at their site of capture. We took four measurements from all live snails and intact dead shells using Vernier calipers: length,

TANE 31, 1985-86 13