Inferior Oolite, in Gloucestershire. 85 



Var. 'a.' shell orbicular, moderately convex; hinge-line oblique, 

 short and curved. Var. k //.' shell transversely ovate, rather flattened ; 

 hinge-line straight, lengthened and nearly horizontal ; the character 

 of the surface, though variable, has nothing peculiar to either variety 

 of figure ; the encircling costoe are narrow, elevated, widely separated 

 and nerer quite regular ; the interstitial spaces have numerous encir- 

 cling lines, which are serrat id or indented, forming a finely granulated 

 surface ; there is also occasionally an obscure rib to be traced within 

 them ; the posterior side has an oblique longitudinal fold, posterior 

 to which the shell is more compressed, and the costae curve nearly at 

 angles to the other surface ; the posterior border is likewise 

 slightly truncated and angulated at it3 junction with the ventral 

 border. 



217. Ceromya striata, syn. Cardita striata. Sow. Min. Con.t.89. 

 f. 1, but not Isocardia striata, Roemer, t. 1 .i. 1, which is likewise 

 a Ceromya, and of which latter shell Ceromya injiata, Agassiz, is a 

 synonym. The present or Sowerby's species has the stria; longitu- 

 dinal, in the other they are transverse. 



212. Tancredia donaciformis ; transverse, subtrigonal, smooth, mo- 

 derately convex ; unibones mesial ; posterior border slightly concave, 

 posterior extremity rather pointed, anterior border straight, obliquely 

 sloping, ventral border rounded ; length f ths the breadth. 



113. Tancredia sulcata-, small, transverse, subtrigonal or donaci- 

 form ; umbones mesial, surface very finely striated concentrically 

 with an anterior dorsal longitudinal ridge grooved at the angle ; the 

 striae anterior to the sulcus rise at a right angle with the others. 



228. Cucullcea amcena ; rhomboidal, fornicated ; umbones large, 

 mesial, distant, both extremities of the hinge-line angulated ; poste- 

 rior dorsal ridge acute, the surface posterior to it concave ; there are 

 also several irregular longitudinal ribs upon each side of the shell ; 

 the middle portion of the surface has- only encircling striae. 



224. Area rudiuscula ; transversely elongated ; width 2 J times 

 the length ; borders elliptically curved ; a wide longitudinal mesial 

 depression; longitudinal costae irregular and rugose, nearly evanes- 

 cent upon the middle portion. 



250. Modiolarca ovata, syn. Area ovata (Buckman) ; oblong, 

 ovate, very gibbose ; umbones anterior, very large, touching each 

 other; hinge-line curved, its extremities rounded; ventral border 

 sinuated by a wide mesial depression, but which does not reach the 

 umbones ; surface imbricated with longitudinal closely arranged waved 

 and tlattened costae, crossed by densely imbricated transverse lines; 

 lines of growth few and strongly marked. The diameter through the 

 umbones is equal to that of the shell longitudinally. The general 

 figure is nearly that of a very gibbose Modiola, but the character of 

 the surface agrees with that of the Arcacea. 



231. Cucullcea triangularis (Phillips?); subtrigonal, rather flat- 

 tened; hinge very oblique to the ventral border, and nearly at right 

 angles to the posterior border, which is straight and elongated ; ante- 

 rior border much shorter, rounded ; umbones oblique, nearly mesial ; 

 surface with exceedingly tine d ting striae producing a finely gra- 



