58 SUPPLEMENT TO GREAT OOLITE MOLLUSCA. 
a slightly concave, posterior area; the base is sinuated posteriorly ; the sides of the valves 
have closely arranged, regular, delicate, longitudinal striations. ‘The nucleus is smooth, 
The anterior side is more produced and less inflated than Jsocardia tenera, Sow., 
from which, also, it differs in having an acute posterior angle. When the external shining 
surface has been abraded, it becomes the Jsocardia triangularis of Bean, with radiating 
striations, which indent the longitudinal ridges, a feature of which there are analogous 
examples in some species of Ceromya, Pecten, &c. The inner border of the valyes 
is crenulated, and the ultimate stage of growth is distinguished by a deeply grooved, 
longitudinal fold. 
Length, 14 lines ; height, 11 lines ; diameter through the valves, 10 lines. 
Geological Position and Locality. 'The Cornbrash of Scarborough, in which it is not 
uncommon. | 
Lucina stRiaTuLA, Buv. (var.). Tab. XX XVIII, fig. 7. 
LucINA sTRIATULA, Buvignier. Paléont. de la Meuse, Atlas, p. 12, pl. 12, figs. 6, 7, 8. 
Testa orbiculari, depressa, striis concentricis, tenuibus, interdum majoribus et strus 
radiantibus obsoletis decussata; cardine subbidentato ; impressione musculari anteriore 
longa, angusta, posteriore obovata ; impressione palleali rugosa, substriata, sulco obliquo 
incurvo notata. (Buvignier.) 
Shell suborbicular, depressed, inequilateral; anterior margin horizontal and nearly 
straight ; outline of the borders of the valves rather irregular; the surface with very deli- 
cate, densely arranged, and a few distant, large, concentric striations, decussated by nume- 
rous faintly marked, longitudinal lines; anterior muscular impression lengthened, narrow, 
the posterior one obovate ; the pallial impression rugose, with an obliquely curved sulcus, 
Height and transverse diameter equal. 
The original of our figure is less transverse than that of M. Buvignier, but in other 
particulars strictly agrees with it ; it is much less convex then Z. rofundata, Roem., and 
the surface ornamentation is quite distinct, but the outline of the two species is very 
similar. 
Geological Positions and Localities. Collected in the Great Oolite of Kirklington, 
Oxon., by Mr. Whiteaves. M. Buvignier records it from the Upper Coral Rag of the 
Meuse. Casts which are not uncommon in the Coral Rag of the southern counties of 
England appear to belong to the same species. 
