lOO GIBBONS : ON OMALONYX UNGUIS AND O, FELINA. 



0/nalonyx felina (as observed in Demerara) differs from the 

 above in being somewhat smaller and more tumid, and in having 

 the posterior end more abruptly pointed ; the spots too are larger, 

 darker, and more numerous, and consequently the longitudinal 

 streaks appear less prominent. 



The shell is distinguishable from that of O. unguis by its 

 more oval and less oblong shape, by being flatter and more 

 depressed, and by having the spire smaller, less twisted, and 

 altogether more rudimentary; viewed from below, less of the spire 

 is visible than in the other species; lastly there is a difference in 

 the color, O. tinguis being a bright amber, while this is more of a 

 dull greyish straw color. 



Mr. Guppy's description of the Trinidad mollusc was origin- 

 ally published in the 'Proceedings of the Scientific Association of 

 Trinidad' (Dec, 1872); as this publication may not be easily 

 accessible to some of the readers of this journal, and as Mr. 

 Guppy's remarks are of very great interest, I take the liberty of 

 extracting the following. At page 4 he says: — "I have been 

 "favoured by Governor Rawson, C.B., with a specimen of 0. 

 '^ imgins,Y€v., from Guadelupe. That shell is faithfully repre- 

 " sented in 'Woodward's Manual of the MoUusca' (pi. xii., fig. 24), 

 " and it scarcely differs from the Trinidad form. I do not know the 

 "soft parts of the Guadelupe mollusc, but it appears to me that a 

 " question here arises — the soft parts of O. unguis, as figured by 

 " D'Orbigny, are different from the Trinidad mollusc. D'Orbigny's 

 "animal was from South America, but Ferussac's type appears to 

 " have been the Guadelupe shell. It may then possibly turn out that 

 " D'Orbigny's species is not the same as Ferussac's. Should the 

 " latter prove to be identical with the Trinidad shell, the name 

 " given by me must be abandoned, and a new appellation given 

 "to D'Orbigny's; but it is not improbable that all three are really 

 "distinct, for in a group like Omalonyx, where the shells are 

 " rather deficient in very marked characters, it may easily be that 



J.C., ii., April, 1S79 



