CARBONIFEROUS FOSSILS OF IRELAND. 155 



Atrypa LATICOSTA. Pltil. SP. 



Terebratula laticosta. Phil. Pul. Fos. 



A few fragments of a large Atrypa, with broad, rounded, transversely striated ribs, liavc been referred to 

 this species with doubt. 



Atrypa NANA. MCoy. (PL XXII. fig. 1<J). 



Sp. Ch. — Orbicular, or slightly ovate, compressed, beak pointed; surface radiated with about ten, straight, 

 equal, obtusely angular ridges, none of which reach the beak. 



This little species resembles the T. radialis in form, but is much flatter, and has considerably fewer, larger, 

 and more angular ribs, all of which disappear before reaching the beak, as in the A. subdentata and rotunda. 

 Sow., from both of which it is distinct, by its greater flatness, and more numerous radiating ridges ; it is also 

 much smaller than any of those shells. Length two lines, width two lines. 



Atrypa ? oblonga. Sow. 



Atrypa oblonga. Sow. Geol. Trans. 

 A few very obscure casts, resembling Mr. Sowerby's figure of this rather doubtful species, have occurred. 



Atrypa? OBTUS A. M'Coy. (PL XXII. fig. 20). 



Sp. Ch Orbicular, convex ; length and width equal, depth two-thirds the width, margin very obtusely 



rounded ; surface marked with rather distant, smooth, concentric strias. 



The margin of this species is broadly rounded, and the edges being thickened, give, particularly to old 

 individuals, a peculiarly rugged character to this portion of the shell, very unusual in the genus Atri/pa ; the 

 concentric lines are very delicate and more distant than those of the A. concentrica, scarcely interrupting the 

 smoothness of the surface; the thickened edges and obtusely rounded margin distinguish it from the A. con- 

 centrica and other allied species. It probably should be referred to Athyrit. Length one inch two lines, width 

 the same, depth ten lines. 



Atrypa platyloba. Sow. sp. 



Terebratula platyloba. Sow. Min. Con. 

 This very depressed variety of the A. acuminata is not uncommon in several localities. 



Atrypa pleurodon. Phil. sp. 



Terebratula pleurodon. Phil. Geol. York. 



Sp. Ch. — Transversely oval; mesial elevation large, square, with several large, acutely angular plaits, 

 which reach to the beak, forming deep notches or teeth in the margin. 



This species is exceedingly variable in the number of the mesial and lateral plaits, but in all instances they 

 are acute, and extend perfectly distinct to the beak, which characters serve to distinguish all the varieties ; the 

 lateral plaits are of unusually large size, and form deep notches in the side margin. The form also varies con- 

 siderably, but the character of the ribs seems to distinguish the species under all its modifications. Length nine 

 lines, width one inch. 



Atrypa prisca. Scldottheim. sp. 



Terebratulites prisons. Schlottheim. Petref. — Terebratula afEnis. Sow. Min. Con. 

 Sp. Ch. — Longitudinally ovate or subtrigonal; front very narrow, rounded; sides nearly straight; beaks 

 small; ventral valve most convex; surface covered with very numerous, rounded strise, which frequently 

 branch as they approach the margin, and are crossed by close, imbricating lamina; of growth. 



