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 Isocardia tenera, Sow., 

 from which, also, it differs in having an acute posterior angle. When the external shining 

 surface has been abraded, it becomes the Isocardia 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 valves 

 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 STKIATULA, Buv. (var.). Tab. XXXVIII, fig. 7. 



LUCINA STRIATULA, Buvignier. Paleont. de la Meuse, Atlas, p. 12, pi. 12, figs. 6, 7, 8. 



Testa orbiculari, depressa, striis concenlricis, tenuibus, interdum majoribus et striis 

 radiantibus obsoletis decussata ; cardine subbidentato ; impressione musculari anteriore 

 lont/a, anyusta, 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 L, 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. 



