1867.] DR. J. E. GRAY ON THE CALYPTR^ID^. 7S7 



3. Crepipatella lingulata, Brod. 



The internal plate with a subcentral radiating fold, forming a notch 

 in the margin of the lip. 



4. Crepipatella dorsata, Brod. 



The apex rather above the margin. 

 Ilab. Vancouver Island. 



2. Crypta, Humphrey. 

 Crepidula, Lamk. 

 Sandaliian, Schum. 



Shell oblong, elongate. Apex submarginal, subspiral. Internal 

 lamina concave, covering about half the cavity. The lip transverse, 

 nearly straight, or with a slight subcentral notch. 



Messrs. H. and A. Adams formed the genus Inacus for the white 

 flat specimen of this genus. All the specimens of the different species 

 that take up their residence in the inside of the shell assume this 

 form and colour. It has been suggested that, instead of being de- 

 pendent on the accident of locality, their living in such places is a 

 habit peculiar to the species, and a proof that they are of a distinct 

 kind. This theory is set at rest by the fact that some specimens of 

 the shell show the two states ; that is to say, an animal growing on 

 the outside of a shell has moved to the inside, and an animal that 

 commenced life on the inside of a shell has moved to the outside. 

 In the first case the apex of the shell is convex and brown, and the 

 circumference white and flat ; and in the other the apex is flat and 

 white, and the circumference brown and convex. I have seen one 

 specimen in which the animal has moved twice, and the shell has a 

 brown lip and margin and a white flat intermediate space. 



The change of form, surface, and colour of the shell of this 

 family was described in my paper, published in the ' Philosophical 

 Transactions' for 1838, and reprinted in Johnston's 'Letters on 

 Conchology;' so there is less excuse for the formation of species, 

 much less genera, on such characters. 



* Apex lateral, posterior, subspiral. Crepidula. 



1 . Crypta aculeata. 



Crepidula acideata, Lamk. Patella aculeata, Grmelin. 



C. echinus, Brod. 



C. hystrix, Brod. 



C. californica, Nuttall ; Chenu, Man. f. 2355, 2356, 2359. 



Surface with spiral lines of spines or small scales. 

 Hab. Jamaica ; Rio Janeiro ; Honduras ; California ; Australia ; 

 Sydney ; Kurrachee ; Natal ; Japan. 



2. Crypta costata, Deshayes (Chenu, Man. f. 2353). 

 Shell with broad spiral ribs, sharp-edged above. 



