CARBONIFEROUS FOSSILS OF IRELAND. 157 



deep as almost to divide the shell into two lobes. Martin describes the beak of this species as perforated, but I 

 think it must have been from accident, or perhaps wear, as some specimens now before me seem perfectly im- 

 perforate. Length six lines, breadth four lines. 



Atrypa semisulcata. M'Coy. (PI. XXII. fig. 15). 



Sp.Ch. — Orbicular, depressed; beak small; mesial fold broad, flat, with about five, strong, rounded, 

 radiating ridges, continvied to the beak ; sides smooth, or very finely striated longitudinally. 



This species is very remarkable, from its coarsely ridged mesial fold, and nearly smooth sides. ' Length 

 seven lines, width eight lines. 



Atrypa striatula. Sow. 



Atrypa striatula. Sow. Geol. Trans. 



A few nearly hemispherical casts in decomposing slate are the only data we have for the occurrence 

 of this species in Ireland, they shew a very fine striation on some parts of the surface ; Mr. Sowerby's original 

 description and figure appear to have been from equally imperfect specimens ; before receiving his definition, 

 I considered the Irish fossils to belong to the genus Orthls, although they are too imperfect to be certain of 

 the fact. 



Atrypa sublobata. Portk. 



Atrypa sublobata. Portk. Geol. Eep. 



I feel the definition of this very remarkable species so difficult, that I must refer to Captain Portlock's 

 figures and description, from which the reader will gain a much clearer idea of the species than I could convey. 

 I may, however, state, that in the same locality, namely, the red sandstone of Kildress, Cookstown, I have ob- 

 served all the forms noticed by that author. 



Atrypa sulcirostris. Phil. sp. 



Terebratula sulcirostris. Pliil. Geol. York. 



Sp. Ch. — Transversely oval, tumid; front much elevated, with about five large, rounded, distinct plaits, 

 which are continued to the beak ; there are usually four broad, flattened plaits on each side, which do not reach 

 the beak, but fonu large, acute notches in the margin. 



This species receives Its specific name from the prolongation of the jneslal plaits to the beaks, giving them 

 a sulcated appearance. The lateral plaits are broader than the mesial ones, greatly flattened, and disappear 

 when they reach about half way to the beak. Length seven lines, width six lines. 



Atrypa triangularis. Sow. 



Atrypa triangularis. Sow. Geol. Trans. 



A few very obscure specimens have occurred, resembling some of the smaller varieties of the A. acumi- 

 nata, but I have referred them provisionally to Mr. Sowerby's species. 



Atrypa triplex. M'Coy. (PL XXIL fig. 17). 



Sp. Ch. — Transversely oval, gibbous ; beaks very small, pointed ; surface with nine short, angular ribs, 

 which reach but half way to the beak ; front elevated with three of the ridges ; the three ridges on each side 

 slightly larger than the mesial ones. 



This pretty little shell is remarkable for its three equal lobes, of three ridges each, it is distinguished from 



2R 



