738 DR. J. E. GRAY ON THE CALYPTR.EID^. [JunC 27, 



Var. 1 . Shell convex, with brown spiral streaks. 

 Var, 2. Shell flat, pure white. 



3. Crypta porcellana, Adams; Lamk. 



Shell smooth, often irregular, costate, tubercular, or granulated 

 from the form of the surface of the body to which they are or were 

 attached. 



Var. 1. Shell convex, coloured, varied with stripes or spots; on 

 the outside of shells or on rocks. 



Patella porcellana, Linn. 



Crepidula porcellana, Lamk . 



Crepidula fornicata. Patella fornicata, Linn. (Chenu, Man. 

 f. 2354?). 



C. arenata, Brod. 



C. excavata, Brod. 



C aplysioides, Reeve. 



C. onyx. Sow. 



C. marginulis, Brod. 



Var. 2. Shell flat, often concave above, white; living inside of 

 shells or in cavities. 



C. nivea et C. squama, Brod. 



C. navicelloides, Nuttall. 



C. glauca. Say. 



C. unguiformis, Lamk. 



C. exuviata, Nuttall (see Chenu, Man. f. 2360, 2362). 



Surface altered by the body to which it is attached : — 



Crepidula lirata. Reeve. 



C. rvgosa, Nuttall. 



Hab. ? 



In Messrs. Adams's ' Genera of Shells,' the species here united 

 are scattered among the three subgenera Crypta, Crepipatella, and 

 Inacus, the latter being formed from the specimens that happen to 

 take up their abode in the cavities of shells. It was this extraordi- 

 nary distribution of species so nearly allied as to be regarded as 

 derived from the same brood or set of eggs, that induced me to under- 

 take to make notes on them. More than one species may be com- 

 bined in these synonyms, which may be distinguished by some dif- 

 ference in the teeth or other organs of the animal, where the animals 

 from different localities have been examined and compared ; and if the 

 specimens from different localities prove to be distinct, each doubtless 

 will furnish the varieties in shape and surface produced by the form 

 and surface of the body to which they may happen to be attached. 



4. Crypta sitchana. 



Shell smooth, covered with a paleaceous periostraca ; inner lip 

 flat, arched inwards. 



Crepidula sitchana, Middend. 

 Hah. Sitcha. 



