CREPIDULA. 



any volution, is extremely short, and its point or verte?^ 

 is obliquely inclined towards the margin. The under side 

 is generally concave, and the inner lip forms a broad, 

 flattish, sharp-edged, toothless, horizontal plate, which 

 about half covers the aperture. Outer lip rather sharp- 

 edged, entire. Muscular impressions within, The out- , 

 side of the shells of this Genus are for the most part . I 

 covered with a thin epidermis, under which are the lines 

 of groAvth parallel to the edges of the shell, and transverse 

 striae or grooves, sometimes muricated with short spines 

 and imbricated scales. Those species which are nearly 

 orbicular approach very nearly to the Calyptrcece, Nei- 

 ther of these genera have any operculum. 



Of recent species the number with which we are ac- 

 quainted is very limited; we have represented one, the 

 finest we have seen, with which we are obligingly favoured 

 by W. J. Broderip, Esq., it forms part of his splendid col- 

 lection, and is remarkable for the contrast between the 

 brilliant dark colour of the inside and the onychine white- 

 ness of the septum. 



Several fossil species are found in the tertiary forma- 

 tions, as well as in those of more recent origin : it is 

 however desirable to distinguish the little fossil shell 

 published in the Dictionnaire des Sciences Naturelles by 

 M. De France under the name of Crepidula ^ItavillensiSy 

 which, if it be not properly arranged under Neritinay 

 where we have placed it, should be considered as a species 

 of our Pileohfs, to which indeed a similar fossil has 

 already been added by M. Deshayes in his account of this 

 latter Genus published in the Annales des Sciences Natu- 

 relles for February, 1824, and which Genus it appears he; 

 had intended to call Tomastoma. 



Fig. 1. Crepidula fornicata. 



2. Onyx, Nob, 



3. • costatUf Nob. 



4. • aculeata. Patella auricula, Gm. 



5. dilatnta. 



g. unguiformis. 



7. Porcellana ? 



