70 MOLLUSCA FROM THE GREAT OOLITE. 



horizontali producto, postice subrostrato, attenuate ; margine cardinali subrecto, oblique 

 declivi ; costis concentricis crebris imbricatis ; margine interno integro. 



Shell thick, convex, transversely elongated, uinbones large mesial ; anterior side pro- 

 duced subhorizontal ; posterior side more attenuated, slightly rostrated ; hinge border 

 nearly straight, elongated, and sloping obliquely ; concentric costae densely arranged, 

 regular imbricated ; inner margins of the valves smooth. 



A very rare shell readily distinguished from other contemporaneous species by the 

 finer and more densely arranged costae. 



Height 16 lines; length 25 lines; diameter through both the valves 13 lines. 



Locality. Minchinhampton Common, where it occurs in the bed of coarse planking. 



Corbis lajoyei, Var. eingenda. Tab. VII, fig. 1 1 . 



Testa ovate-rotundatd concentrice costatd ; costis magnis subdistantibus prominulis 

 lamettiformibus ; latere anfico brevi, margin/bus- rotundis. 



Shell ovately rounded, convex, concentrically costated ; costae rather distant, regular, 

 prominent, lamellar, anterior side short, margins rounded. 



The figure is less elongated than in the preceding species, more especially the anterior 

 side ; the costae are much more distantly arranged. 



Height, one inch ; length, an inch and a quarter ; rare. 



Locality. Minchinhampton Common, in the bed of coarse planking. 



Corbis aspera. Tab. VII, fig. 13, 13a. 



Cokbis aspera, Lycett, Ann. Nat. Hist., Dec. 1850, pi. 11, f. 7. 



Testa ovate-elongatd, convexd, umbonibus subacutis prominulis, costis concentricis 

 subacutis regnlaribus distantibus. 



Shell ovately elongated, convex, umbones prominent, mesial, rather acute ; concentric 

 costae regular, distinctly arranged, and rather acute. 



Compared with C. eingenda, the figure is more elongated, the umbones more pointed, 

 and the costae are more elevated and distantly arranged. 



Height, S lines, length, 1 1 fines ; but larger specimens occur in the Inferior Oolite. 



Localities. Minchinhampton Common, in the Great Oolite ; the vicinity of Nailsworth, 

 in the Inferior Oohte. 



Sub-Genus, Sph^ra, Sow. 



Shell thick, subaequilateral, equivalve, globose, umbones large, contiguous, directed 

 forwards, luuule small, but slightly excavated, ligament external, surface smooth, or 

 impressed only with the folds of growth. Hinge, massive, with two cardinal teeth in the 

 right valve, these are thick and united beneath the umbo ; the posterior one is prominent, 

 and placed transversely to the hinge plate, the anterior one is oblique and elongated 



