CARBONIFEROUS FOSSILS OF IRELAND. 81 



Meleagrina TESSELLATA. Phil. SP. 

 Avicula tessellata. Phil. Geol. York. 



Sp. Ch. — Semicircular, liingc-line straight, ears acute; posterior car undefined, once and a half the lengtli 

 of the anterior car; surface with fourteen or fifteen distant, rounded, radiating ridges. 



This is a very boldly-formed species ; the few large, distant, radiating ribs giving it a strongly- 

 marked character ; the spaces between the radiating ribs are smooth, and slightly concave ; they are crossed by 

 distant, imbricating lines of growth ; the posterior ear is not distinctly defined from the body of the shell. Length 

 eight lines, width nine lines. 



Pteronites. il/' Coy. 



Gen. Ch. — Equivalve, transversely elongate, very much compressed; beaks small, nearly terminal; ante- 

 rior side very small ; a sinus in the front margin, under the beak ; posterior side very wide, subtruncate ; 

 hinge-liue exactly equal to the width of the shell ; no hinge teeth. 



This genus contains a number of very similar little shells, intermediate in character between Avicula 

 and Modiola; they resemble Avicula in their very oblique form, large posterior side, and compressed contour; 

 but they diSer from them in the hinge-line never being extended into a lengthened wing, and in being 

 equivalve, while their want of cardinal teeth distinguish them at once from the genus Pterinea of Goldfuss ; 

 the length of the hinge, and compressed, flattened form, distinguish them from the Modiola:. The following 

 species are the only ones I have seen of the genus : 



Pteronites angustatus. MCoy. (PL XIII. fig. 6). 



S]i. Ch. — Width three and a half times the length; surface with very obscure wrinkles, parallel witli the 

 posterior margin ; anterior end very small, pointed ; posterior end obliquely pointed. 



This shell is distinguished from the others of its genus by its more slender form ; the front margin and 

 hinge-line form an acute angle, the anterior end being bluntly pointed ; the posterior end is also pointed, the 

 margin rounding directly from the extremity of the hinge-line ; the surface has some small, obscure wrinkles 

 parallel to the posterior edge. Length six lines, width one inch eight lines. 



Pteronites latus. M'Coy. (PL XIII. fig. 7)- 



Sp. C/;.— Transversely triangular, width rather more than twice the length; beaks convex, prominent; 

 anterior end small ; a distinct sinus in the front margin below the beak ; posterior end broad, subtruncate, 

 slightly emarginate. 



This species is well distinguished from the P. angustatus, M'Coy, by its great length in proportion to its 

 width : there is an obsolete sulcus running from the beak to the posterior extremity, and obscui-e indications of 

 distant striae, parallel to the posterior margin. Length eight lines, width one inch five lines. 



Pteronites semisulcatus. M'Coy. (PL XI. fig. 32). 



Sp. Ch. — Transversely trigonal, gibbous; beaks small, tumid, nearly terminal ; hinge-line equal to the 

 width of the shell ; much elevated, rectangular ; anterior and posterior sides of the shell smooth ; about seven 

 or eight obtuse, rounded ribs extend obliquely from near the beak to the inferior posterior end. 



This species is remarkable for having only a few radiating ribs on the middle of the shell, having the sides 

 perfectly smooth, with the exception of a few delicate lines of growth ; the hinge-line considerably elevated and 

 compressed ; the beaks prominent ; anterior side very small, tumid ; sinus in the front margin moderate. Width 

 ten lines. 



X 



