VOL.37 NO.1 APRIL 2007 - British Shell Collectors' Club

PALLIDULA Page 16
Diagnosing subspecies
characteristics –
main diagnostic shell characteristics (MDSC)
taxon↓ dorsum base and margins interstices of teeth
E. onyx onyx
brown with two white
broad longitudinal bands
dark brown to black
dark brown to black
E. onyx adusta
tinged light to dark brown
without white bands
brown
brown to dark brown
E. onyx melanesiae
tinged light to dark brown
without white bands
brown to dark brown
brown to dark brown
It is interesting to mention that the shells of the two peripheral subspecies separated geographically by the vast
area of the Indian Ocean – E. onyx adusta and E. onyx melanesiae – are almost identical and they are
practically not separable without knowing the exact locality, their base and dorsum are tinged light to dark
brown. It is possible that in the future, when more conchological information is available, they will be united in
one subspecies.
Shells in intermediate zones connecting all subspecies of E. onyx have sometimes mixed characters: in the
same area entirely brown shells can be found together with shells having whitish transverse dorsal bands or
whitish longitudinal dorsal bands of different width. There are reports in the literature regarding finding of
several entirely brown shells in Southern Thailand and these shells were for some time treated as E. onyx
melanesiae. Until now, there is no conchological evidence confirming the existence of another species in the
onyx-group, separated from E. onyx by a conchological gap without intermediates. A conclusion can be drawn
that Erronea succincta must remain a synonym of Erronea onyx.
The taxonomic history of E. nymphae is discussed in Heiman (2006). This taxon is perhaps a mutant and can
be treated as a form until more information confirms the existence of its living population is known. The five
nymphae-like shells mentioned in Sowerby (1870) are still preserved in Mss Saul’s collection, now in the
Zoological Museum of the Cambridge University.
Literature
Dodge, H. 1953. A historical review of the mollusks of Linnaeus. Part 2. The class Cephalopoda and the genera
Conus and Cypraea of the class Gastropoda. Bulletin of the American Museum of Natural History 103(1). New
York. 134 pp.
Heiman, E.L. 2006. Intraspecific variation in living cowries. Part 2. An electronic book on a CD.
Lorenz F. & Hubert, A. 1993. A Guide to worldwide Cowries. 571 pp. Christa Hemmen Verlag, Wiesbaden,
Germany.
Raybaudi, L.M. 1989a. Cypraeidae:genus Erronea-subgenus Adusta. For a revision of the onyx group. TC 21:2-
3.1989b. Cypraeidae (Subgenus Adusta Jousseaume, 1884). TC 21:4-10.
Schilder F.A. & Schilder, M. 1938. Prodrome of a monograph on living Cypraeidae. Proceedings of the
Malacological Society of London 23:119-231.
Schilder M. & Schilder F.A., 1971. A catalogue of living and fossil cowries. Institut Royal des sciences naturelles
de Belgique. 246 pp.
Sowerby, G. B. I. 1870. Thesaurus Conchilyorum Vol. 4.
* e-mail address of the author: heimel@netvision.net.il