230 J. F. BLAKE ON THE KIMMERIDGE CLAY OF ENGLAND. 



4 of height. The other valve is smaller, and with the ribs nearly 

 obsolete. Average breadth 1 in. 



This appears to have been called Av. incequivalvis ; but, though 

 it is inequivalve, it differs from that species in having much finer 

 ribs, with the small intermediate ones, and is altogether a more 

 delicate shell. 



Generally in the Lower Kimmeridge, but chiefly at the base, 

 especially at Woodhall-Spa pit. 



AVICULA NTJMMULINA, n. Sp. PI. XII. fig. 3. 



Beak -\ from the anterior end, which is strongly convex, stretching 

 half the breadth of the hinge-line beyond it ; posterior side also 

 convex, but slightly so, meeting the hinge-line at at angle of 100° ; 

 ornaments concentric rounded ribs, and fine, numerous, regular 

 transverse ones ; the concentric ribs strongest near the umbo, gradu- 

 ally giving way to the others ; shell excessively compressed, like a 

 Nummulite except for the posterior angle ; nearly as high as broad ; 

 average breadth 1 in. 



In the upper zone of Lower Kimmeridge, near Market Rasen. 



AVICULA VELLICATA, 11. Sp. 



Hinge-line very short. The general shape is that of an oval 

 with the axis making an angle of 55° with the hinge, the ends of 

 which join the oval by two tangents ; umbones moderately elevated, 

 having a pinched appearance along the axis of the oval ; ornaments 

 strong concentric bands fimbriated in the intervals by very fine 

 radiating stria? ; diam. about f in. 



Common in Upper Kimmeridge, Lincolnshire. 



AVICULA DORSETENSIS, n. Sp. 



Shape somewhat similar to the last, but with a long narrow 

 wing added behind, which the posterior border meets in a gentle 

 curve. It is, however, not so oblique, and more nearly round ; outer 

 surface nearly always covered by a thick coat of the matrix, which 

 adheres to it (? from there being a strong epidermis) ; when clear 

 it has faint transverse ribs. 



In the Lower Kimmeridge, Eingstead; also in Lincolnshire and 

 in the Oxford clay. 



Lima jedilignensis, n. sp. PL XII. fig. 9. 



Very oblique, almost like a short Lithodomus ; main axis making 

 an angle of 60° with the hinge ; inflated ; beaks prominent ; greatest 

 length 1 J inch, along main axis ; breadth perpendicular to this, less 

 than | inch ; ornaments very fine, regular, close -set striae, which 

 fimbriate the concentric lines of growth. 



Rare in the Lower Kimmeridge, Lincolnshire, near the base. 



Pecten midas (D'Orb.). 



Pecten nitescens (Phillips). 



t)'Orbigny's short description (Prod. vol. ii. p. 54) might answer 



