Additional statistical study

In shells of E. lamarckii lamarckii the dorsal spots are partially ocellated with purplish grey whereas in E. lamarckii redimita ocellations are found sporadically and mainly on the shell sides. This statement is checked statistically below in order to learn whether these subspecies can be separated conchologically using this shell character. The results can be seen in Table 1.

Table 1

Shell characteristics and formae of different populations of E. lamarckii

(the percentage of shell with a given shell characters and formae in populations of different areas)

It follows from Table 1 that in the majority of shells from Mozambique (83%) the dorsal spots are ocellated with purplish grey. On the contrary, in 91% shells from Thailand these ocellations are absent. These data confirm the assumption that two geographically separated subspecies: E. lamarckii lamarckii (Gray, 1825), the nominal subspecies, and E. lamarckii redimita (Melvill, 1888) can be singled out because they conform to the criterion for diagnosing cowry subspecies.

Formae—nine formae of lamarckii are recognized in this study as listed in alphabethical order in Table 1.

Forma confused is characterized by the dorsal pattern irregularly confluent, displaced or distorted—Fig. 11. This forma is known in many cowry shells with an elaborated dorsal pattern: Erosaria macandrewi (Sowerby, 1870), Erosaria nebrites (Melvill, 1888), E. turdus (Lamarck, 1810) and many others.

Forma deformed is known in practically all cowry species—Fig. 14; it can be characterized by different kind of deformations usually of mechanical origin.

Forma dilatata: shell stunted, heavy, often small, margins calloused, thickened, or expanded—Fig. 9; it occurs in both subspecies and is especially frequent in the Phuket area.

According to the Prodrome “In redimita two ecological varieties can be distinguished in the whole area inhabited by the race: oblong shells…with angular margins, produced extremities, flattened base, finer and long columellar teeth and more conspicuous lateral spots than in the stunted callous shells (=inocellata Schil. 1930).” Calloused shells of E. lamarckii redimita, which are often also smaller than typical shells of the subspecies, can be treated as forma dilatata.

Martin, (1991) and Doneddu & Manunza (1993) reported an unusual population of E. lamarckii from Phuket, Thailand with small, calloused shells (f. dilatata).

Such shells are not only known in E. lamarckii redimita but also in the nominal subspecies and in several other species (Heiman, 2002) in the genus Erosaria.

Forma “golden”: shells are of an unusual appearrance because the upper layer of the dorsal pattern is absent—Fig. 10. One such shell has even been described as a new species Erosaria sharoni Walles, 1980 (now considered a synonym).

A similar phenomenon is known in shells of E. turdus pardalina (Dunker, 1852), Erosaria erosa (Linnaeus, 1758), Erosaria nebrites, Cypraea tigris (Linnaeus, 1758), and other cowry species.

Forma incurvata: the outer lip seems to be longer than the inner lip forming an “laughing” impression—Fig. 13. Shells of this kind have been described as a new species Erosaria incurvata Walles, 1980 (now considered a synonym).

Forma pallida: general coloring paler, markings often smaller and sometimes whitish—Fig. 8. The extreme case of this variety is f. albinotic when the dorsum has a very pale to almost white coloration—Fig. 12.

Forma rostrata: extremities produced, often recurved, base may be thickened or aperture abnormally dilated. I have only encountered this rare forma in shells from East Africa—Fig. 15.

Forma saturata: shell very richly colored to rather dark, but markings as usual—Fig. 4. This forma seems to be of clearly environmental origin and can be found in many cowry species.

Forma suffused: shell (or at least the dorsum) suffused with a uniform layer of rich white, gray, bluish, green, pink, fulvous, chestnut or blackish enamel often including particles of mud or sand—Fig. 16.

In practice, several formae may be combined (f. combined), for example, an unusual shell may be deformed with a confused dorsal pattern and so forth—Fig. 14.

Acknowledgements

I would like to thank Werner Massier (Namibia), Mike Woodcock (Canada), Rika and Fernand Dedonder (Belgium), Jean and Janine Demartini (France) for providing a background conchological material for this article, Henk K. Mienis (National Mollusc Collectios at the Department of Evolution, Systematics & Ecololgy, Hebrew University of Jerusalem and Zoological Museum, Tel Aviv University, Israel) for providing malacological information for this work and Solly Singer for reading and discussing the manuscript.

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