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BRITISH CARBONIFEROUS BRACHIOPODA. 



the dorsal valve, which generally projects beyond the level of the beak, the curious 

 convexity of the smooth lateral portions of both valves, and especially of the ventral one, 

 which present the unusual appearance of hanging below the margin (as noticed by Sowerby), 

 are not, to my knowledge, characters ever seen in B. acuminata. The last-named shell is 

 also generally much more elevated in front, and the frontal commissure of the valves is 

 peculiar, and different from that of B. reniformis. 



The shell under description is usually transverse, with three or four ribs on the fold, 

 and two or three in the sinus ; five on the fold, and four in the sinus, are of much rarer 

 occurrence. In the ' Geology of Yorkshire,' Professor Phillips represents two specimens, 

 without mesial fold or ribs, as varieties of B. reniformis, but it appears doubtful to me 

 whether these very exceptional specimens are properly defined. 



Loc. Bh. reniformis is not a rare fossil in the Carboniferous limestone of Bolland, of 

 Settle, in Yorkshire, at Twiston, in Lancashire, and in the Isle of Man, &c. In Ireland, 

 Sowerby mentions Dublin and Cork, and Mr. Kelly adds Lisnapaste, Millecent, and 

 Little Island. I am not certain whether the species really occurs in Scotland, at least I 

 have not seen any well-authenticated examples. 



Rhynchonella cordiformis, Sowerby. Plates VIII, IX, X. 



Terebratula cordiformis, Sowerby. Min. Con., vol. v, p. 495, tab. ccccxcv, fig. 2, 1825 > 

 Atrypa — M'Coy. Synopsis of the Carboniferous Fossils of Ireland, 



p. 152, 1844. 



Rhynchonella — Morris. A Catalogue of British Fossils, p. 446, 1854. 



Spec. Char. Obscurely pentagonal, either slightly wider than long or longer than wide ; 

 dorsal valve gibbous, front much elevated, with three or five ribs on the mesial fold, 

 which become obsolete before reaching the extremity of the umbone ; profile arched ; the 

 lateral portions of the valve are convex and tumid. In the ventral valve the beak is small 

 and often adpressed ; the sinus is wide and deep, with from two to four ribs along its 

 middle ; the lateral portions of the valve are smooth, and do not hang below the margin 

 of the opposite one. Dimensions variable ; three examples have measured — 

 Length 13^, width 16^, depth 16 lines. (Sowerby's type.) 

 „ 12, „ 14, „ 13 „ 

 » 9, 10, ,, 9 ,, 



Obs. It is with much doubt and many misgivings that I here provisionally introduce 

 Ter. cordiformis as a separate species, and in this respect I have followed both Professors 

 M'Coy and Morris. Sowerby describes his shell as " heart-shaped ; front much elevated, 

 with a deep sinus in the margin ; sides rather convex, sharp edged ; middle ornamented 

 with several acute furrows reaching to the beaks ;" that it " differs from Ter. acuminata 



