18:2 BRITISH CARBONIFEROUS BRACHIOPODA. 



convexity from several of those represented in my plate." The area, I am ready to admit, 

 is certainly wider in both Mr. Sowerby's specimens than in those belonging to Mr. 

 Ormerod (figs. 1 — 6), but the area generally varies much in its width in specimens of a 

 same species, as I have already often had occasion to notice. Mr. Sowcrby's second 

 example (not figured in the 'Min. Conch/) is an incomplete interior of the ventral valve, 

 in which, from the shell being young and shallow, the muscular impressions could not be 

 as deep or as indented as in adult, very convex and thickened valves, such as is the 

 original specimen figured in the ' Mineral Conchology/ or those illustrated in my plate 

 (figs. 3, 4) ; nor could I perceive that the interior of Sowerby's specimen varied in any 

 essential particular from those more perfect examples I had examined. In any case, fig. 7 

 must be regarded as the typical shape of C. con/aides, of which the other specimens figured 

 by me are probably variations. 



Chonetes comoides does not appear to be a very common species, and all the speci- 

 mens hitherto procured are from the Carboniferous limestone. It has been found in 

 England and in Ireland in the following localities : — Llangaveni and Beaumaris, in 

 Anglesea; Llanymynech and Tidenham Chase, in Gloucestershire; Chepstow, Treflach 

 Wood, south-west of Oswestry; Bundoran, County Donegal; and Lough Erne, 

 Fermanagh. On the Continent it appears to be equally rare ; Prof, de Koninck 

 mentions having found a single specimen at Vise, in Belgium, and that he possesses 

 another example from Sable, in France; that Count Keyserling has found it in the 

 Carboniferous limestone at the banks' of the River Ylytsch, in the Ural, and that the 

 Museum of St. Petersbnrgh possesses examples from the neighbourhood of Switschei, a 

 village on the banks of the Ugra, in the Government of Kaluga, in Russia. 



Chonetes papilionacea, Phillips. PI. XLVI, figs. 3 — G. 



Pectinites flabellifoemis, Lister. Hist. Conch., lib., iii, pi. 475, fig. 31, lo'88. 

 Spibifera papilionacea, Phillips. Geol. of York., vol. ii, pi. ii, fig. (5, 1836. 

 Chonetes papilionacea, Be KonincJs. Description des Anim. foss. du Terr. Carb. de 



Belgique, pi. xiii, fig. 5, and pi. xiii bi3 , fig. 1, 1843; and 

 Monog. du genre Chonetes, pi. xix, fig. 2, 1847. 

 multidentata, M'Coy. Synopsis of the Char, of the Carb. Fossils of 

 Ireland, pi. xx, fig. 8, 1844. 

 — papybacea, M' Coy ? Ibid., pi. xx, fig. 2. 



Spec. Char. Shell thin, sometimes rather large, transversely semicircular, depressed, 

 slightly concavo-convex, but almost flat when young. Hinge-line straight, and as long as 

 the width of the shell. Ventral valve slightly convex at the beak, but much flattened at 

 the sides, and especially so near the cardinal edge ; beak small, and not protruding beyond 

 the cardinal edge ; dorsal valve very gently concave along the middle, lateral portions 

 much flattened ; a well-defined area is present in each valve, the ventral one, which is 

 the widest, being divided in the middle by a triangular fissure, partially arched over by 



