Collecting Marginellidae on the Cape Peninsula

by Alan Seccombe
Photography by Alan Seccombe

The Cape Peninsula is a narrow strip of land that runs from Cape Town in the north to Cape Point, 77km to the South. In most places, the peninsula is less than 10km wide, bordered by the Atlantic Ocean on the west, and False Bay on the east. Despite the small geographical distances, the molluscan fauna of the Atlantic and False Bay coastlines differ markedly. The Marginellidae are a good example of this, with many more species occurring in the warmer water of False Bay.

Some of the small species survive the rough seas intact and wash ashore in good condition. The very small species, mostly uniform white in colour, can only be found by patient sieving of shell grit. Live material of the commoner species can be collected intertidally, in rock pools at low water; others occur only in the subtidal region and are only commonly collected by scuba diving; and others are active only at night and collected by scuba diving at night.

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The diving conditions in the Cape are more akin to diving around the shores of the UK than diving in the tropics – cold water (15° in False Bay), preponderance of kelp, poor visibility and often rough seas. On the Atlantic Coast, the best place to collect live Marginellidae is Kommetjie, a small village very popular with the crayfishing and surfing fraternity. On the left-hand side of the slipway is a rocky shore with large boulders on the upper shore and much smaller rocks and tidal pools in the lower shore.

Marginella rosea Lamarck, 1822 is common in the pools from the mid-tide level downwards, crawling in the open, especially at the turn of the incoming tide. The shells are a drab grey-white, 20mm or less, and the animal is a milky white with red spots. Turning the rocks in the pools should yield many Volvarina zonata bilineata Krauss, 1848, 7mm, a white shell with a narrow brown band at the median and posterior, often clinging to the underside of the rocks or in the many dead shells of Patella granatina. Volvarina zonata biannulata Fabricius, 1826 is smaller than the previous species and much less common, it is a chestnut brown with white bands at the anterior and posterior. It is usually found partially buried in silty sand.

Marginella rosea Lamarck, 1822

Marginella lineolata Sowerby, 1886

On the lower shore, the other small species are found under rocks – Dentimargo neglecta Sowerby, 1846 and Hyalina cylindrica Sowerby, 1846. Both are less frequent than those mentioned previously, but not uncommon provided that the tide is low enough. Dentimargo neglecta is small, 3–5mm, and is usually found on the underside of rocks in crevices, or in silt or shell grit. Hyalina cylindrica occurs in three forms: the most common form is pale fawn in colour; ponsonbryi Sowerby, 1897 is a striking golden amber colour; and multizonata Krauss, 1852 has brown/orange lines. Both the latter forms are only rarely found at Kommetjie, but more abundantly in False Bay.

The real prize is the rare Marginella lineolata Sowerby, 1886. The False Bay form is very different from the Eastern Cape specimens, being larger and having a much paler background, and fine black spots. Marginella lineolata is found in coarse sand usually where wave action has caused undulation of the sea bed.

Diving off Kommetjie yields a larger paler form of Marginella rosea, but no other Marginellidae. At Olifantsbos, a marine reserve in the Cape of Good Hope Reserve, a form of Marginella rosea is found with wavy axial lines, the so-called strigata form. The False Bay side of the Cape Peninsula provides a much wider variety of locations for good shore collecting, and a number of rewarding dive sites for day and night diving. The Marginella fauna is also more varied.

There are a number of marine reserves where collecting is prohibited. The main shore collecting sites are at Glencairn, Windmill Beach and Buffels Bay (in the Cape Nature Reserve, but collecting is permitted). Dive sites include Fishoek Beach, Sunny Cove (restricted marine reserve), Windmill Beach/Froggy Pond and Buffels Bay. Buffels Bay is also good for collecting beach shells.

The tidal swimming pool at Glencairn has a large population of Prunum capensis Krauss, 1848 and it is easily collected there without the use of snorkel or SCUBA. Prunum capensis is also very common in shallow water in sand near rocks and in sand pockets on rock reefs all along the coastline, and readily emerges following disturbances of sand. This species is quite variable in pattern and colour ranging from uniform yellow, beige to banded forms. Pure white specimens are not uncommon.

At Windmill Beach, the False Bay form of Marginella rosea Lamarck, 1822 can be found in sand in shallow water, emerging at the turn of the tide, and occasionally in low water tidal pools. Marginella rosea from this location are larger than their Atlantic counterparts and usually with attractive pink/purple amongst the grey pattern. An occasional specimen is covered in a golden overlay. At Buffels Bay, shells are usually deep purple in colour and larger. Specimens taken in 10–20m are also quite different from the intertidal forms.

The rocky shore at Buffels Bay is home to the False Bay Volvarina varieties: Volvarina zonata Kiener, 1841 with a wide central band; Volvarina dunkeri Krauss, 1848, a small yellow shell with a subsutural brown line; Volvarina cleo Bartsch, 1915, a larger pure white or yellow shel; and Volvarina zonata bilineata Krauss, 1848 are all found under stones in low water pools. Dentimargo neglecta Sowerby, 1846 is also found, but rarely.

The larger and more attractive Marginella are found diving at night. Both in Fishoek Bay, and at sites near Simons Town, night diving in 15–20m can yield all the species on a single dive. The particular dive sites are not difficult, and are made from the shore with easy entry and exit points.

Marginella flocatta Sowerby, 1889 is very variable, very common, and prefers a more coarse substrate. Marginella nebulosa Roding, 1798, the largest Marginella in the area, is common in certain areas, usually on fine sand close to rocky outcrops. Marginella confortini, which looks like a dwarf Marginella nebulosa, and is very similar to the Marginella bairstowi Sowerby, 1886 from the Eastern Cape, is uncommon, and is usually collected with Marginella flocatta. Marginella piperata Hinds, 1844 exhibiting a wide variety of patterns and colours, and Marginella strigata Sowerby, 1889, which has continuous fine brown stripes, are uncommon, but when found are found in numbers.

Marginella flocatta Sowerby, 1889

Marginella strigata Sowerby, 1886

Other Marginellids which appear to be fairly common are the micro-Marginellas found in beach drift. The most common species, which are pure white in colour, are Persicula algoensis E.A. Smith, 1901, Persicula bensoni Reeve, 1865 and the very tiny Persicula pseutes E.A.Smith, 1904.

The Cape Peninsula therefore offers the Marginella specialist, and shell collectors generally who dive, the opportunity to collect 16 species of Marginella relatively easily. Any collectors visiting the Cape are invited to contact me, and I will be pleased to provide guidance to the exact sites, and also to arrange for a night dive. The best night diving in False Bay is between May and September.

I have Marginella from the Cape and many other shells available for sale or exchange. A list is available on request.

Visitors to South Africa should note that a permit is required to collect shells dead or alive, and shell grit. Permits are obtainable at Post Offices for a fee of R50 currently (£5 per annum). There are also many marine reserves where collecting of any marine organisms is not permitted. Details of these can be obtained from the Department of Seafisheries, or from myself.

This article by Alan Seccombe was first published in our magazine Pallidula in April 1999.

Marginellas from the Cape Peninsula
Dentimargo neglecta Sowerby, 1846
Hyalina cylindrica Sowerby, 1846
-form multizonata Krauss, 1852
-form ponsonbryi Sowerby, 1897
Marginella confortini Bozzetti, 1992
Marginella flocatta Sowerby, 1889
Marginella lineolata Sowerby, 1889
Marginella nebulosa Roding, 1798
Marginella piperata Hinds, 1844
Marginella rosea Lamarck, 1822
Marginella strigata Sowerby, 1889
Persicula algoensis A. Smith, 1901
Persicula bensoni Reeve, 1865
Persicula pseutes E.A. Smith, 1904
Prunum cepensis Krauss, 1848
Volvarina cleo Bartsch, 1915
Volvarina dunkeri Krauss, 1848
Volvarina zonata Kiener, 1846)
-form biannulata Fabricius, 1826
-form bilineata Krauss, 1848