CARBONIFEROUS FOSSILS OF IRELAND. 63 



This is by a great deal the smallest species of the genus, scarcely equalling in size the numerous Entomos- 

 traca of the shales in which it occurs, and wliicli it much resembles to the naked eye. Length about one- 

 twentieth of an incli. 



AXINUS. Sow. 



Gen. Ch. — Axiniform ; posterior side short, rounded, with a long ligament placed in a furrow along the 

 entire edge ; posterior side produced, angulated with a small lunule under the beak ; surface smooth. 



AxiNus AxiNiFORMis. Portk. SP. 



Amphidesma axiniformis. Portk. Geol. Eep. (Without references). 



Sp. Ch. — Rhomboidal, slightly oblique, depressed; length and width nearly equal; beaks prominent, acute, 

 nearly central ; anterior side subtruncate, rounded ; posterior side very slightly oblique, convex ; an oblique 

 ridge from the beak to the posterior angle ; surface smooth. 



This species has frequently a glossy membranous expansion round the margin of the valves, visible on the 

 shale in which it occurs. Length nine lines, width ten lines. 



AxiNUS CAEBONARIUS. Portk. SP. 



Amphidesma carbonaria. Portk. (Without references). 



Sp. Ch. — Orbicular, compressed, smooth, or very finely striated transversely; length five-sixths of the 

 width ; beaks small, central ; anterior and posterior sides equal, the latter slightly truncated. Length ten lines, 

 width one inch. 



AxiNUS CENTRALIS. M'Coy. (PL XI. fig. 8). 



Sp. Ch. — Trigonal, depressed, smooth; beaks central, or nearly so; posterior slope truncated; posterior 

 end obtusely pointed ; anterior side narrow, rounded. 



This is distinguished from every other Axinus I know, by its triangular outline, and nearly central beaks ; 

 the body of the shell is flattened, the ventral margin nearly straight, and the surface perfectly smooth. Length 

 four lines, width five lines and a half 



AxiNUS DELTOIDEUS. Phil. SP. 

 Cypricardia deltoidea. Phil. Pal. Fos. 



Sp. Ch. — Ovate, deltoidal, depressed, smooth; posterior side obliquely truncated, defined by a sharp 

 angle or keel, extending from the beak to the posterior angle ; anterior margin convex. 



This species is described by Professor Phillips as a Cypricardia ; he, however, notices the resemblance it 

 bears to the Axinus ohscurus of the magnesian limestone ; the examination of some good specimens leaves 

 no doubt on my mind that they are of the same genus : the two valves of the present species are usually found 

 together, and are perfectly alike. Length nine lines, width eleven lines. 



Axinus NucuLoiDES. M'Coy. (PI. XL fig. 9)- 



Sp. Cli. — Transversely ovate, length two-thirds the width, convex ; beaks small, one-third the width from 

 the anterior end, broad, rounded; posterior side attenuated, pointed, extremity rounded; ventral margin 



