﻿104 



BRITISH CARBONIFEROUS BRACHIOPODA. 



able to discover the original examples in the Gilbertsonian collection ; the conclusions here 

 recorded are therefore based upon an examination of the figure only, for the few words of 

 description which accompany it do not materially assist. 



Thirdly, — Rhynchonella Davreuxiana, De Koninck (PI. XXIII, figs. 18 — 20), (De 

 Koninck, ' Animaux Eossiles qui se trouvent dans le terrain Carbonifere de la Belgique.' 

 Supplement, p. 664, 1851). 



Notwithstanding the superior authority of my distinguished friend, Professor De 

 Koninck, I cannot help feeling impressed with the idea that the form above named is only 

 a small thick variety, or local race of R. pleurodon (?). None of the specimens I have 

 been able to examine (and which were all obtained at Gilling, by Mr. E. Wood) did 

 exceed 3^ lines in length, 4 in width, and 2\ in depth. In the larger number of 

 specimens, three and four ribs were prevalent upon the fold, but in some others five could 

 be counted ; the ribs generally extend from the beak and umbone to the margin, but 

 sometimes, as was the case with certain young shells of R. pleurodon, the ribs became 

 obsolete close to the extremity of the beaks. Should my present views relative to this 

 shell be considered erroneous, palaeontologists will do right in adopting Professor De 

 Koninck's specific denomination, and I may observe that the specimens of R. Davreuxiana 

 figured in my plate, were so determined by the Belgian author himself. 



Fourthly. — RhynchonelJa triplex, M'Coy, sp. (pi. xxiii, figs. 16 — 18) ; Atrypa triplex, 

 M'Coy, « Synopsis of the Carb. Foss. of Ireland,' p. 157 (pi. xxii, fig. 17, 1844). 



Professor M'Coy describes his shell as "transversely oval, gibbous; beaks very small, 

 pointed ; surface with nine short, angular ribs, which reach but half-way to the beak ; 

 front elevated with three of the ridges ; the three ridges on each side slightly larger than 

 the mesial ones. This pretty little shell is remarkable for its three equal lobes, of three 

 ridges each ; it is distinguished from the A. raricosta, Phillips, by the ridges extending 

 only half-way to the beaks on the ventral valve, and its very small size. Length, two 

 and a half lines; width, three lines." In our Plate XXIII, fig. 17 is copied from the 

 ' Synopsis.' 



No locality is given, but Mr. Kelly supplies the deficiency, by informing us that the 

 shf;ll was found in yellow or reddish sandstone, forming the base of the Carboniferous 

 system, at Kildress, in Tyrone ; and he kindly furnished me with specimens of the sand- 

 stone, which I found to contain, in addition to casts of Spiriferina octoplicata, Athyris 

 ambigua, St. crenistria, and R/i. pleurodon, many examples of M'Coy's Atrypa triplex; 

 and although some few of the specimens of the last did present exactly the characters 

 described by the author, still it was easy to perceive that this little Rhynchonella varied as 

 well as all other species of the genus in the number of its ribs ; and on the same slab 

 could be seen specimens which connected by gradual passages R. triplex to R. pleurodon, 

 proper, and of which I believe it to be the fry. All the fossils above enumerated as 

 occurring in the sandstone of Kildress are in the state of casts, and the ribs in some of 

 the examples referable to R. triplex, extend much further along the surface of the valves 



