CARBONIFEROUS FOSSILS OF IRELAND. 67 



obliquely incurved in the present genus : these fossils resemble the Saxicava, but as a genus they are at once 

 distinguished by being regular, while the irregularity of form in the species of Saxicava, is so essentially con- 

 nected witli their habits that it becomes of importance ; on the whole, tlie nearest approach among recent shells 

 to our fossil genus, is perhaps Dr. Leach's genus Tkracia. 



Leptodojius fragilis. M'Coy. (PL X. fig. II). 



Sp. C%.— Transversely oval, gibbous; shell very thin; surface with regular, sharp, elevated, concen- 

 tric striae ; five-sixths of the width ; anterior side large, rounded ; posterior side slightly narrowed, subtrun- 

 cate; beaks large. 



This shell is so ob'S'iously related to the Corbula cjujantea of the Greensand, that I have no hesitation in 

 placing it in the same genus, at the same time that I do not think either of those shells congeneric with the Cor- 

 bula of our coasts, and that they should rather form a distinct genus which would be found only in the fossil 

 state. The present species is very convex ; the beaks large, tumid ; the shell is exceedingly delicate ; the con- 

 centric striae are extremely regular, small, but sharp and distinct, they are distant and smooth. Length one Inch 

 eight lines, width two inches two Hues. 



Leptodomus senilis. Phil. sp. 



Corbula senilis. Phil. Geol. York. 



Sp. Ch. — Transversely oval, gibbous; surface with very irregular, transverse wrinkles. 



This Is easily distinguished from the L.f raff ills, M'Coy, by the thick, rugged. Irregular ridges which cross 

 the surface. Instead of the delicate, sharp, regular striation of the latter species ; the beaks are very larwe and 

 gibbous. Length one Inch three lines, width two inches. 



Venerupis ciNGULATUs. M'Coy. (PI. X. fig. 1). 



Sp. CA.— Transversely elongate, oval, cylindrical, very convex; beaks close to the anterior side, which is 

 very small, rounded ; posterior side elongated, obliquely truncated, rounded ; surface with about ten or eleven 

 large, angular, concentric ribs, which are sometimes crossed by fine, longitudinal striae. 



In this species the concentric ribs are very regular; they are large, angular, and sharp above. Lentrth four 

 lines, width seven lines. 



Venerupis obsoletus. M'Coy. (PI. XI. fig. 16). 



Sp. Ch. — Transversely ovate, convex ; surface with about ten obtuse, concentric ribs on the sides, becoming 

 obsolete on the middle of the shell. 



From its strong, general resemblance to the V. scalaris, I have placed this shell In the present genus, rather 

 than in Pullastra, to which it seems closely allied ; the surface is uniformly but slightly convex ; the beaks 

 rounded, but prominent ; sides concentrically marked, with slightly convex wrinkles, which disappear before 

 they reach the middle of the shell ; the surface is otherwise perfectly smooth ; the form Is remarkably rounded 

 in all its parts. Length seven lines, width eleven lines. 



Venerupis SCALARIS. M'Coy. (PL X. fig. 6). 



Sp. Ch. — Transversely ovate, short, very gibbous; beaks large, prominent, close to the anterior end, which 

 Is small ; surface with about ten large, angular, concentric ridges. 



This is one of the most strongly-marked fossils of the carb. limestone, and its large, smooth, angular, con- 



