128 BRITISH CARBONIFEROUS BRACHIOPODA. 



ventral valve is slightly concave, the beak alone presenting a small convexity ; while the 

 dorsal one is moderately convex, with a mesial furrow or depression. The surface of both 

 valves is closely covered with numerous radiating, imbricated striae, a smaller one or two 

 intervening between the larger, as in 8. crenistria. The typical specimen measured, length 

 19^, width 28^, depth 5 lines. 



Professor M'Coy has stated that his species " seems to be constantly distinguished from 

 0. crenistria, by its deep rounded mesial furrow, which indents the frontal margin ;" 

 but it is not always more convex than 8. crenistria, nor are the angles in the last always 

 acute, for many examples had them rounded, as in 8. Kellii. It is quite true that the 

 striation is so variable a character as to be of little use in specific distinctions, in the 

 British species of Streptorhi/nchus ; but, at the same time, I cannot allow that, in all the 

 examples of 8. Kellii that have come under my observation, the striation was finer, closer, 

 or more equal than is commonly the case with 8. crenistria, although such is the case in 

 many individuals. 



In England, 8. Kellii has been found in the Black Rock, Clifton. In Scotland, it 

 occurs in Ayrshire. In Ireland, at Monaghan ; Annghilla, three miles south-west of 

 Ballyganty in Tyrone, &c. 



Var. C— S. cylindrica, M'Coy. PI. XXVII, fig. 9. 



Orthis cylindrica, M'Coy. Synopsis of the Characters of the Carboniferous Fossils 



of Ireland, p. 123, pi. xxii, fig. 1, 1844. 



Almost circular, hinge-line shorter than the greatest width of the shell, with rounded 

 cardinal angles: area triangular, not very wide ; fissure covered by a pseudo-detidium. 

 Ventral valve convex at the beak, concave from near the middle to the margin ; dorsal 

 valve very convex, almost geniculated. Surface covered with numerous radiating striae, 

 of which two or three smaller ones intervene between the larger ones. Of this beautiful 

 species or variety (?) I have never been able to obtain the sight of any other besides the 

 type, which measures eighteen lines in length, by twenty-one and a half in breadth, 

 and ten in depth. 



Professor M'Coy observes that, in this species, the striation is similar in character to 

 that of 0. crenistria, 0. Kellii, and L. euglypha, but that the form at once distinguishes 

 it from every known species. 



It is at all times hazardous to make a new species upon the inspection of single 

 examples ; and as my knowledge in the present instance does not extend beyond the one 

 figured in the ' Synopsis,' I dare not venture to conjecture too closely as to its probable 

 affinities or variations in shape. The original example in Sir R. Griffith's coljection is 

 said to have been found in Arenaceous Limestone at Castle Espie, Comber, Ireland. 



