SPIRIFERA. 57 



almost upon a level. The dorsal valve not quite so deep or convex as the opposite one ; 

 mesial fold defined, but not much elevated above the level of the valve. In the ventral 

 valve the sinus extends from the extremity of the small incurved beak to the frontal margin ; 

 hinge line and area as long as the greatest width of the shell, to which the lateral margins 

 of each valve rapidly converge, producing acute terminations. The area is of moderate 

 width, and divided by a small triangular fissure. External surface finely striated (?). 



Length 4|, width 14, depth 4 lines, 



Obs. I am acquainted with but a single imperfect individual of this shell, the original 

 type forming part of Gilbertson's collection now in the British Museum. Professor 

 Phillips states the surface to be finely radiated ; but the Museum specimen, which is 

 deprived of almost all its shell, is nearly smooth, showing indications of radiating striae, 

 but at the umbone and in the vicinity of the cardinal edge ; therefore, from such imperfect 

 material, it is hardly safe to conjecture as to the condition of its external sculpture. It is, 

 however, probable that in the perfect shell the surface may have been such as was 

 described by Professor Phillips, and this opinion appears to be strengthened from the fact 

 that an American mountain limestone Spirifer, collected at Clifton, Illinois, by Mr. 

 Worthen, closely resembles in shape the shell under description, and the external surface 

 of which is finely striated. Sp. fusiformis cannot be confounded with Sp. cQtwoluta, 

 Phillips, or Sp. subconica, Martin, on account of the difference in the character of its 

 surface, which could not have been strongly ribbed. 



Loc. Bolland. 



SriRIFERA RHOMBOIDALIS, M'Coy. PI. XII, figS. 6, 7, 



Maetinia RHOMBOIDALIS, M'Coy. Synopsis of tlie Carboniferous Tossils of Ireland, p. 141, 



pi. xxii, fig. 11, 1844. 



Spec. Char. Rhomboidal, gibbous, slightly wider than long ; hinge line much shorter 

 than the width of the shell ; cardinal angles rounded ; beak of the ventral valve small, 

 much iiicuived, with a deep wide, angular sinus extending from the extremity of the beak 

 to the front; area small, fissure partially covered by a pseudo-deltidium. In the dorsal 

 valve the mesial fold is prominent and almost angular from rapid slope of its lateral 

 portions ; surface of both valves ornamented with numerous small radiating obscurely- 

 rounded ribs. 



Length 9, width 10, depth 7 lines. 



Obs. This shell does not appear to have often exceeded the dimensions above given, 

 and is easily distinguished by its rhomboidal shape, almost angular elevated fold, deep 

 linguiform sinus, and small undefined rounded ribs. Professor M'Coy's original example 

 was derived from the Carboniferous limestone of Cork, and I possess another from 



8 



