135 



has seen this shell affixed to the root of the Isis nobilis 

 or stony red coral, but very rarely with both the valves. 

 In Sowerby's Genera of Shells this genus is very mi- 

 nutely described. 



Crania personata. 

 [There are also four fossil species.] 



ORBICULA. 



PATELLA ANOMALA. 



Midler, table S, fig. 1,7. 

 This shell has been mistaken for an univalve by most 

 writers on Conchology. Poli, however, calls one of the 

 species, A nomia turbinata; but subsequent investiga- 

 tion has proved it a bivalve: the lower vrlve, which is 

 extremely thin, and closely adhering to marine bodies, 

 had escaped the notice of former naturalists; and the 

 upper one might consequently easily be mistaken for a 

 Patella, which it nearly resembles, having a more or 

 less pointed and elevated summit. Shell suborbicular, 

 inequivalve, without an apparent hinge; lower valve 

 extremely thin, flat, and adhering; upper valve subcorn- 

 eal, summit elevated. The animal is a true Brochio- 



