UPPER, OR FLINTY CHALK. 213 



The hinge is a longitudinal furrow, transversely crenulated, extending 

 on one side of the beaks only; its direction, as it regards the transverse 

 diameter of the shell, being generally obUque. 



There are several species, and many varieties, and in some speci- 

 mens the characters are so much blended as to be distinguished with 

 difficulty. The shell represented in fig. 1, Tab. xxvii. is an excellent 

 type of the genus, and is probably the most perfect specimen hitherto 

 discovered. 



83. Inoceramus Cuvieri. Tab. xxvii. fig. 4. Tab. xxviii. figs. 1. 4, 



Convex, with large, obtuse, distant, transverse costae ; surface covered 

 with numerous linear lameDaj; hinge side depressed, expanded; posterior 

 side flat, nearly smooth; beaks small, reflexed; hinge oblique. 



The number of the costee varies from eight to twelve; they are large 

 and rounded, and extend with a gentle sweep across the valves, being 

 gradually lost in the expanded anterior side. The surface is covered with 

 transverse lines, and possesses a lameUated structure, appearing as if com- 

 posed of a succession of tliin plates; but the substance of the shell is per- 

 fectly sohd, and consists of fibrous calcareous spar. The posterior side 

 is nearly flat, and smooth; the hinge is placed obliquely. The com- 

 parative width and length of this species cannot be determined, since no 

 perfect specimen has been discovered. 



The adult shell attains a gigantic size; a specimen in ray possession 

 must, when entire, have exceeded three feet in length, and twenty inches 

 in width. Fragments of the hinge of a corresponding magnitude are not 

 uncommon, some of them being more than 1-5 inch wide, and 1-2 inch 

 thick. 



This species is named in honour of the illustrious Cuvier, to whose 

 researches the comparative anatomist, and the geologist, are so greatly 

 indebted. 



Tab. xxvii. fig. 4, fragment of the hinge, exhibiting the transverse cre- 

 nulated sulci. 



Tab. xxviii. fig. 1, a specimen, the interior of which is filled with flint. 

 fig. 4, represents the upper and lower valve of the same 



