382 CARBONIFEROUS LAMELLIBRANCHIATA. 



umboaes to the inferior border, but no evidence of any notch. I have remarked 

 before of several genera of Carboniferous Laniellibranchs that the byssal sulcus 

 was present, probably as an ancestral relic. Such a character is markedly 

 present in all species of the genus Sanguinolites. M' Coy's figures of his ovate 

 varieties show the contour of the valves very perfectly, but the peculiar arrange- 

 ment of the markings of the surface are not well brought out or commented 

 upon. 



I have been fortunate enough to see the hinge-plate in a small example, 

 PL XLIV, fig. 6, where it is seen to be narrow and edentulous ; but there is no 

 trace of any external or internal ligament to be made out. 



Sanguinolites V-scriptlfs, sp. nov. Plate XLII, figs. 5 — 7. 



Specific Characters. — Shell below the medium size, somewhat inequilateral, 

 subquadrate, compressed, carinate. The anterior end is comparatively large, 

 comprising about a quarter of the valve, compressed, its dorso-ventral diameter 

 very little less than that of the posterior extremity, with a bluntly rounded 

 margin, most prominent towards the antero-inferior angle. The inferior margin 

 is gently and regularly convex, the postero-inferior angle being well marked and 

 a rounded right angle. The posterior margin is straight, obliquely truncate from 

 above downwards and backwards, making a slightly obtuse angle with the hinge- 

 line. The latter is only slightly arched, and is shorter than the inferior margin. 

 The umbones are tumid, incurved, contiguous, pointed, much elevated above the 

 hinge-line, and placed a little in front of the central dorso-ventral diameter of the 

 valve. An oblique swelling passes downwards from the umbo to the postero- 

 inferioi" angle, separating the small but compressed dorsal slope from the rest of 

 the valve, the convexity of which is interrupted by a narrow but well-marked 

 sinus, passing from the apex of the umbo to the inferior margin. Lunule small ; 

 escutcheon elongate and comparatively large. 



Interior. — Unknown. 



Exterior. — The surface is ornamented with flattened ribs and sulci, close and 

 narrow in the umbonal region, but becoming larger and further apart as they 

 approach the margin. The ridges have the following curious arrangement : — 

 Arising as very thin lines near the anterior margin, they descend parallel to the 

 margin, and, soon becoming stronger and rib-like, are interrupted as they cross 

 the shell by the narrow sinus which passes from the umbo to the inferior margin. 

 The ribs then pass backwards with an upward curve, so that they are concave 

 downwards, and the posterior limb of the curve is produced lower than the 



