169 



Calceola. Shell inequivalve, triangular, turbinated, flattened beneath; the 

 largest valve hollowed or hood-shaped, obliquely truncated at the aperture. 

 The cardinal margin straight, transverse, a small notch or indentation in the 

 middle; the superior margin arched; the small valve flat, semi-orbicular, 

 opercular, having a tubular on each side of the cardinal margin, and, in the 

 middle, a pit with a small lamina. 

 1 fossil species. 



Discini. Shell inequivalve, oval-rotundate, rather depressed valves, 

 nearly equal, each having an orbicular disk in the centre, very distinct; disk 

 in the upper valve not perforated, with a mamillated protuberance in the 

 middle; that in the other valve very white, divided by a very small trans- 

 verse slit. 



D. ostreoides. 



Birostrites. Shell inequivalve, bicornate, the disk of the valves elevated 

 conically, unequal, obliquely diverging, nearly straight, the one enveloping the 

 other at the base. 



1 fossil species. 



Crania. Shell inequivalve, suborbicular, lower valve almost flat, perfo- 

 rated in the internal surface by three unequal and oblique holes; the upper 

 valve very convex, furnished interiorly with two prominent callosities. 



C. personata, 4 fossil species. 



BRACHIOPODA.— Three Genera. 



Shell bivalve, adhering to marine bodies, either directly, or by a tendinous 

 cord. 



Orbicula. Shell suborbicular, inequivalve, without any apparent hinge; 

 lower valve very thin, flat, adhering to marine substances; the upper valve 

 subcorneal, the upper more or less elevated.* 



O. Norwegica. 



Terebratula. Shell inequivalve, regular, subtriangular, attached to 



* I have not been able to meet with any shell agreeing with the above description, 

 no 



