BIVALVIA. 35 



squamatis, intervallis, triplolatioribus ; costis extremis minoribus ; auriculis subeequalibus, 

 transverse lamellosis. Valva dextra convexiori quinquesulcata, concentrice tenuiter lamellosa ; 

 sulcis concavis, costis altera valva respondentibus ; costis latioribus convexis, subdivisis. 

 (Buvignier.) 



Shell suborbicular, inequivalve, depressed. The left valve nearly flat, with fine radiating 

 ribs, separated by very wide intervals ; the costse have large, squamous plications, rather 

 irregular, and nearly disappearing as they approach the apex, the costse near to the margins 

 being the smaller ; the intervals between the costae have five regular, concentric, squarnous 

 plications ; the auricles are nearly equal, they are transversely lamellated. The right 

 valve is convex, with five radiating sulcations, corresponding to the five costae of the other 

 valve ; the whole surface of the valve is covered with delicate, regular, concentric, closely 

 arranged lamellae. The interior of the valves present an appearance corresponding with 

 the ornamentation of the exterior. 



Height rather greater than the breadth, and thrice the diameter through both the valves. 



Geological Position and Locality. The Cornbrash of Scarborough and of Northampton- 

 shire ; the collections of Mr. Leckenby and of the Rev. A. W. Griesbach contain fine 

 specimens. M. Buvignier quotes the species from the lower ferruginous beds of the Oxford 

 Clay, Ardennes and Meuse. 



HINNITES GRADUS, Bean, sp. Tab. XXXIII, figs. 10, 10 a. 

 PBCTEN GRADUS, Bean. Mag. Nat. Hist., 1839. 



Testa valva sinistra, ovato orbicuJari convexo-plana, radiatim nndulato costata et con- 

 centrice lineata ; umboni acuto submediano, auricula antico magno, oblique radiatim lineatis ; 

 auricula postica subnullo ; costulis radiantibus numerosis, costa una majora et minora al- 

 ternatim instructis, semel varicibus duobus radiantibm magnis. Lineis decussantibus densis 

 regularibus ; valva qffixa ignota. 



Shell with the left valve ovately orbicular, somewhat convex, the surface irregular, with 

 unequal, undulating, radiating costae and concentric lines; umbo acute, mesial straight, the 

 anterior auricle large, with oblique radiating lines, the posterior auricle scarcely produced ; 

 the surface of the valve has very numerous, unequal, radiating, rounded costae, in two series, 

 a larger and a smaller costae being arranged alternately ; there are also two elevated, 

 irregular, large, radiating varices upon the middle of the valve, as in Hinnites abjectus. 

 The cost33 are about equal in width to the intercostal spaces ; the entire surface of the 

 shell has densely arranged, very regular, concentric lines, which are scarcely visible without 

 the aid of a magnifier. The other valve is unknown. 



Nearly allied, both in figure and aspect, to Hinnites abjectus, from which it is dis- 

 tinguished by the regularity and smoothness of the costae and by the regular, concentric 

 lines crossing both the costae and the intercostal spaces; the latter are equal in width to the 



