CARBONIFEROUS FOSSILS OF IRELAND. 53 



PSAMMOBIA DECUSSATA. M'CoiJ. (PI. X. fig. 2). 



Sp. Ch. — Transversely rhomboldal, gibbous ; beak near the anterior end, which is short, rounded; posterior 

 end obliquely truncated ; surface with irregular, transverse sulci, decussated by close, fine, longitudinal striae. 



There is an obtuse ridge separating the posterior side from the body of the shell, the transverse sulci are at 

 unequal distances, but the longitudinal striaj are very regular, close, and rounded. Length eight lines, width 

 one inch two lines. 



LUCINA ANTIQUA. M'Col/. (PL VIII. fig. 9). 



Sp. Ch, — Orbicular, slightly convex ; beaks pointed; lunule very small; surface marked with delicate, 

 sharp, concentric strias. 



This handsome species is almost perfectly orbicular, the posterior margin being very slightly angulated ; 

 the lunule is small, but deep, ovate; concentric striaa very fine; it is less convex than most species of the genus. 

 Length one inch three lines, width one inch four lines. 



UnGDLINA ANTIQUA. M'Col/. (PL VIIL fig. 8). 



Sp. Ch — Longitudinally ovate; length one-sixth greater than the width, evenly convex; beaks small, 

 rounded from the posterior side ; a depression in front of the beaks, where the anterior margin is slightly 

 flattened ; sui-face nearly smooth, with an irregular, concentric plication, strongest on the posterior side. 



This singular shell appears so closely allied to the recent Ungulina transversa, that I have included it in 

 the same genus. Length one inch three lines, width one inch one line. 



AmPHIDESMA SUBTRUNCATA. il/'Co?/. (PL X. fig. 10). 



Sp. Ch. — Subquadrate, rhomboidal, depressed, smooth; anterior side rounded; posterior side subtrun- 

 cate, very obscurely flexuous ; beaks small, pointed, subcentral ; surface smooth. 



This species has a very thin, smooth shell ; the beaks are small but prominent ; the posterior end is 

 slightly beaked and flexuous. Length one inch one line, width one inch three lines. 



CORBIS CANCELLATA. M' Coi) . (PL VIIL fig. 14). 



Sp. Ch. — Transversely obovate, one-third wider than long, compressed; shell thick, regularly cancellated 

 by equal, radiating, and transverse, thin, prominent ridges ; beaks large, prominent ; anterior side small ; poste- 

 rior side somewhat attenuated, subtruncate, rounded. 



The thick, regularly cancellated shell induces me to include this fossil in the genus Corhis, for the pre- 

 sent, although it is much more compressed, and inequilateral, than the other species. The general form is ob- 

 ovate, the posterior portion of the shell being perceptibly narrower than the anterior; the beaks project 

 considerably, but are compressed ; they are about two-thirds the length from the posterior extremity. Length 

 one inch tlu-ee lines, width one inch nine hnes. 



Venus centralis. M'Cod. (-P^- ^^- ^S- 6)- 



Sp. Ch. — Transversely oval, convex ; anterior and posterior sides equal or nearly so, rounded ; beaks small, 

 central ; surface marked transversely with close, unequal, rounded ridges. 



This is distinguished from the V. elliptica, Phil., by the almost perfectly central position of the beaks, the 

 transverse wrinkles are also finer and more numerous in the present shell ; they are sharpest at the anterior side. 

 Length two lines, width three lines. The beaks are rather more central than in the figure. 



O 



