CONCHOLOGY. 89 



and adheres to extraneous bodies ; one sub-central muscular 

 impression divided into three. 



Anomia ephippium. Anomia pyriformis. 



A. patellaris. A. fornicata. 



A, cepa. A. membranacea. 



A. electrica, A. squamula. 

 A. lens. 



A. ephippium. The Saddle Anomia. PI. 16, fig. 1. 



Shell sub-orbicular, irregularly wrinkled and waved ; up- 

 per valve convex, under flat and perforated at the hinge, 

 through which passes the ligament by which it is affixed to 

 other bodies ; inside pearly, and of various changing colours, 

 such as green, purple, violet, and yellow. 



6. Crania. The Scull. One species. 



So called from the appearance caused by three holes or 

 cavities on the surface of the lower valve. 



Shell irregular, orbicular, inequivalve ; the inferior valve 

 almost flat, and marked on the interior with four muscular 

 impressions, sometimes very deep, and of which the two 

 sub-central are sufficiently connected to form but one ; the 

 superior valve like a Patella, more or less convex, with four 

 very distinct muscular impressions, rather distant. 



C.personata. The masked Crania. PI. 16, fig. 4. 

 Orbicular; upper valve gibbous and conical, lower valve 

 flat, with three perforations. 



FAMILY XX. 



Brachiopoda. Three genera. 

 1. Orbicula. One species. 

 Greatly resembling a Patella, for which it is often mista- 

 ken on account of the lower valve being very thin, flat, and 

 adhering. 



Shell sub-orbicular, very compressed, inequilateral, very 

 inequivalve ; the inferior valve very thin, adherent, and im- 



M 



