BRITISH SILURIAN BRACHIOPODA. 189 



109. Orthis? Hirmantensis, M'Coy. Dav., Sil. Mon., PL XXXII, figs. 5—9; and 



Sup., PL XI, figs. 8—11. 



When treating of this species at p. 261 of my ' Silurian Monograph,' I had not seen 

 any specimens of the fossil, and M'Coy's figures were not satisfactory, so that all I could 

 do was to reproduce the original description. Subsequently, thanks to my friend, Mr. J, 

 Parrott's exertions, I have been able to study several good examples of the species which 

 he had collected from the Caradoc or Bala shales above the Hirnant Limestone at Aber 

 Hirnant, near Bala. The fossil is abundant in the locality, and occurs in the conditions 

 of impressions of the exterior and of internal casts, but no specimens showing the two 

 valves in position, or the area, have yet been discovered, so that I cannot feel quite 

 certain whether it should be classed with Orthis or SfrojjJiomena. The specimens are 

 also more often distorted or out of shape from the effect of cleavage. When marginally 

 perfect the shell is semi-circular ; the hinge-line is as long as or very slightly shorter than 

 the greatest breadth of the shell, and this does not seem to have much exceeded 8 or 9 lines 

 in length by 10 or 12 in breadth. The ventral valve is moderately convex, the dorsal one 

 very slightly so or nearly flat. The surface of both valves is covered with numerous 

 thread-like radiating radii, some bifurcating, while a shorter riblet is interpolated between 

 the larger ones. The new figures I have given in PI. XI of this Supplement show all I 

 know about the fossil. 



110. Orthis sarmentosa, M'Coy. Dav., Sil. Mon., PL XXXVI, figs. 35—38. 



While reproducing Prof. M'Coy's description of this so-termed species, I had never 

 seen any specimens of the fossil. At p. 60 of his ' Catalogue of the Collection of 

 Cambrian and Silurian Fossils in the Geological Museum of the University of Cambridge,' 

 Mr. Salter states that 0. sarmentosa, M'Coy, is 0. testudinaria in a crushed condition. 

 I question, however, that the Cambridge specimen is a crushed example of 0. 

 testudinaria, Dalraan ; indeed, I feel convinced that it is not so. Mr. Salter has quite 

 misunderstood the characters of Dalman's species, and what he refers to it in the 

 ' Memoirs of the Geological Survey of Great Britain,' vol. 3, p. 371, figs. 5 — 10, belong 

 to an entirely different species and in no way resemble Dalman's type. I know nothing 

 of M'Coy's 0. sarmentosa, and therefore am unable to pass any opinion as to its specific 

 value. 



