The menkeana-riddle finally resolved

The wrong usage of the name menkeana for a large-shelled Bistolida from the Seychelles and Cargados has been a subject of discussion and concern to me. With the following I hope to clarify the situation:

In the last issues that were printed of WorldShells, readers will have noticed the repeated use of the name menkeanaDeshayes 1863 for large, pale Bistolida -specimens from the Seychelles.

The holotype of menkeana is illustrated in Roberts (1885) pl. 4 fig. 69, 70 and also in Martini & Chemnitz (1881). Both illustrate a dark shell in which the marginal spotting is conspicuous and confluent, framing a dark, distinctly zonate dorsum. A look at the holotype specimen itself demonstrates how much fantasy was laid into creating these figures, and it demonstrates the caution one needs in interpreting original illustrations.

Raybaudi first proposed the use of menkeana in The Connoisseur No. 22, p. 45 fig. 136, for a a rather pale specimen somewhat similar to owenii owenii (Sowerby, 1837) figured on the same page, fig. 134. In WS 3, p. 63 fig. 152 B an analogous, still paler specimen is presented as menkeana . The identical shell is again illustrated on the back page of the "Golden Opportunities"- Section of WS 19, again as menkeana . These two shells are claimed to come from the Seychelles, while the locus typicus of menkeana is La Réunion, as my friend Alex Hubert and I have already pointed out in our "Guide". Shells similar to the holotype of menkeana in size and... quality are today common along the beaches of Mauritius.

The holotype of menkeana in the MNHN, Paris, measuring 10 mm: This is owenii owenii.	Fig. 1: menkeana , after Martini & Chemnitz (1881)	Fig. 2: menkeana , after Roberts (1885)   note that these two illustrations are supposed to be the shell on the left!!
owenii owenii, smaller variety from the South of Mauritius. Such a shell was probably the holotype of menkeana.	Fig. 3: menkeana var. modesta , after Sowerby (1870)= owenii owenii	owenii owenii, resembling the var. modesta, from western Mauritius
Bistolida piae Lorenz & Chiapponi 2005. Above: from Cargados Carajus, 22 mm. Below: Seychelles, 22 mm, coll. Perugia

In Sowerby's Theasurus (1870) there is a specimen illustrated as " menkeana var. modesta " on Pl. 31 fig. 333, 334. It well agrees with Raybaudis shells in shape, colour and pattern. Sowerby dwells upon the name menkeana as follows: "In Owenii both extremities are produced like the hinder one in neglecta , but much more distinctly, while, on each side of the callus, at each end, there is a deep flat depression; the base is very flat, the lateral brown dots much crowded on it, and the back is almost angularly elerated. Specimens of this shell have been brought to me as representing C. menkeana , of Deshayes, with which, however, it does not well agree. Sir David Barclay kindly lent me the shell figured in my last Plate (f.514, 515),and believed at the time to represent Deshayes' shell. But, on more careful examination, I am convinced that the latter belongs to our present group. The teeth, more than half across the base, point this out, and the shell which Mr. Hugh Owens names modesta (...) seems to fulfil all the conditions to identify it with menkeana .". Such shells are today found along the west and north coast of Mauritius and represent a variation of owenii owenii.

Ironically, the name modesta is officially introduced only by these words of Sowerby's, who consequently is the author of modesta . By explicitly illustrating the shell on Pl. 31, fig. 333, 334 as menkeana var. modesta he also supplied an illustration of it.

As a consequence, the large orphaned species was described as a new subspecies, Bistolida owenii piae Lorenz & Chiapponi 2005, but the conchological differences, supported by DNA analysis suggest that it is a valid species.

Literature:

F. Lorenz & M. Chiapponi (2005): "Revision of the Bistolida owenii-complex (Gastropoda: Cypraeidae) with the Description of a New Subspecies." Visaya Vol. 1 No. 5 p. 22-36

Sowerby, G. B. I. (1870): Thesaurus Conchyliorum. London. Martini & Chemnitz (1881): "Systematisches Conchylien Cabinett" Bauer & Raspe, Nürnberg

Roberts (1885) "Monograph of the Family Cypræidæ" in: Manual of Conchology, ed. G. W. Tryon (Philadelphia) Vol. 7, p. 153­304 and Plates 1­23

Raybaudi (1989): Connoisseur of Seashells, p. 45, fig. 136 " (1992): World Shells 3, p. 63, fig. 152 B
Lorenz & Hubert (1993): "A Guide to Worldwide Cowries", Hemmen Verlag, Wiesbaden

first uploaded in 2006