ON THE PSEUDO-GENUS PSEUDOMARGINELLA, v. MALTZAN 

 By the Rev. Dr. A. H. Cooke. 



Read 11th November, 1921. 



About forty years ago H. von Maltzan and J. Carriere published ^ 

 certain papers proposing a new genus Pseudomarginella for mollusca 

 possessing the shell, but not the animal, of Marginella glabella, L. 

 The papers attracted attention ^ at the time from the remarkable 

 nature of the conclusions drawn, which amounted to this^ that we 

 are not justified in concluding that similar shells are inhabited by 

 similar animals, or, stated in the reverse way, that two animals 

 of absolutely different anatomical construction may develop shells 

 which are in distinguishable from one another. 



We know, of course, that a limpet-like form of shell is developed 

 by molluscs whose internal anatomy is widely different, and that 

 snails whose soft parts are quite dissimilar may be protected by 

 shells whose spire is similarly coiled. But does the evidence adduced 

 by Von Maltzan and Carriere justify their conclusions in this 

 particular case 1 



In the bay formed by the Isle of Goree, ofi West Africa, in the 

 latitude of the southern C. Verdes, Von Maltzan collected living 

 shells of Marginella glabella, which he gave to Professor Schmidt 

 of Strasburg, and Schmidt passed them on to Carriere (privatdocent 

 of zoology in the University) for examination. 



There were eleven shells in all, six of which, both in animal and 

 shell, proved to be typical M. glabella. Of the remaining five, all of 

 which possessed an operculum, which is quite unknown to Marginella 

 proper, four had an operculum and radula (both figured), which 

 suggested relationship with the " Buccinacea ", while the remaining 

 one had an operculum and radula which suggested relationship to the 

 " Purpuracea ". All five had the shell of a typical M. glabella, 

 but their internal anatomy, so far as it was examined, differed utterly 

 from that species. 



Carriere, believiag that the five last-mentioned specimens were 

 genuine inhabitants of the M. glabella shells, and finding, too (as was 

 not surprising), that they exhibited other points in anatomy differing 

 from M. glabella, proposed the name of Pseudomarginella lejptopus 

 for the four specimens with a Buccinoid — he means unguiculate — ■ 

 operculum, the radula of which, according to Troschel, was closely 



1 Nachr. Malak. Ges., xii, 1880, pp. 106-8 ; Zool. Anz., iii, 1880, pp. 637-41 ; 

 Zeitschr. Wiss. Zool., xxx-sdi, 1882, pp. 99-120. I deal with Carriere's later 

 paper, as being by far the most complete. 



" The editors of the Journ. de Conchyl., xxviii, 1880, pp. 375-6, state that 

 one of these operculate Marginella has been sent to them, and that they 

 propose soon to figure the operculum and radula. I have failed to discover 

 that they ever did so. 



