28 BRITISH CARBONIFEROUS BRACHIOPODA. 



Spirifer triangularis, Be Koninck. Aniraaux fossiles de la Belgique, p. 234, 



1843. 



— ornithorhyncha, M'Coy. Synopsis of the Carb. Foss. of Ireland, p. 133, 



pi. xxi, fig. 2, 1844 ; and British Palaeozoic Fossils in 

 the Camb. Museum, p. 418, pi. iii D, fig. 27, 1855. 



— triangularis, Semenow. Ueber die Fossilien des Schlesischen Kohlenkalkes, 



1854. 



Spec. Char. Triangular, twice as wide as long, with a straight, elongated hinge-line, 

 and slightly concave, nearly parallel-sided area, towards the attenuated extremities of 

 which the lateral margins of each valve converge, forming acute angles with the hinge. 

 The fissure is triangular, and partly covered by a pseudo-deltidium. The dorsal valve is 

 less convex than the opposite one, with an elevated mesial fold, which commonly assumes 

 the character of a single produced and acutely angular cuneiform ridge or rib, at times 

 considerably prolonged beyond the frontal level of the lateral portions of the valve. On 

 either side of this central ridge from six to ten smaller ribs ornament the lateral portions 

 of the valve. The beak of the ventral valve is narrow, produced, and incurved. A shallow 

 mesial sinus commences at the extremity of the beak, and extends to the front ; but at a 

 short distance from its origin a mesial or central rib originates, which becomes wider and 

 more elevated and produced as it approaches the front, and corresponds with the central 

 ridge of the dorsal valve. Seven to eleven smaller ribs exist also on the lateral portions 

 of the valve, on either side of the sinus. The dimensions taken from a perfect individual 

 have produced — 



Length 10|, width 21^, depth 6^ lines. 



Obs. This elegant shell was first described and figured by Martin, from a specimen 

 which, at a subsequent period, became the property of the late J. Sowerby, and of which 

 he gave a somewhat restored illustration in the ' Mineral Conchology/ Through the 

 kindness of Mr. J. de C. Sowerby, I am myself enabled to portray this individual 

 (figs. 16, 17), so that there can exist no doubt as to the identity of the original type. I 

 have said so much to be able to prove that Professor M'Coy was decidedly mistaken when, 

 in 1844 and 1S55, he considered his so-termed Sp. ornithorhjncha to be distinct from 

 Martin's species •} for, after a careful inspection of the last-named author's type (fig. 23), 

 it will be easily seen that the only visible difference between it and Martin's specimen 

 consists in the more or less developed condition of the mesial ridge in either valve. 

 Martin's specimen clearly shows the ridge that originates in the sinus of the larger valve, 

 so characteristic a feature of his species. Sp. triangularis appears to be a rare fossil, both 

 in Great Britain and on the Continent, the only perfect example I have been able to 

 examine being the one in the possession of Mr. Reed, of York (figs. 18 — 21). It here also 

 assumes much of the cruciform aspect described by Professor M'Coy, and is intermediate 



1 Professor De Koninck allows me to state that he entirely coincides in the view here expressed. 



