158 BRITISH CARBONIFEROUS BRACHIOPODA. 



from the small, slightly convex beak, and extending to the front, dividing the valve into 

 two convex lobes. Cardinal area well defined, snbparallel and narrow, divided by a 

 small fissure covered by a pseudo deltidium. Surface ornamented by numerous small, 

 rounded, longitudinal stria?, sometimes bifurcating or increasing in number by intercalation 

 at various distances from the beak, and crossed by numerous small, concentric lines or 

 wrinkles, while about fourteen long, vertical, slender, tubular spines are arranged in two 

 rows close to the cardinal edge. The dorsal valve follows the curves of the opposite one, 

 but has a mesial elevation in lieu of a sinus, and is similarly sculptured. Dimensions 

 variable ; length 7 inches, width 12 lines. 



Obs. Of this remarkable species a few imperfect examples were discovered for the 

 first time by Prof, de Koninck in the Carboniferous limestone of Vise, in Belgium, and 

 who, misled by the well-defined ventral area, supposed his species to be referable to the 

 genus Leptcena. Prof, de Koninck's figures do not represent the perfect condition of the 

 shell, for none of his examples retained the peculiarly extended and reflexed ears which I 

 have drawn with great care from some very perfect specimens discovered by Mr. Burrow 

 in the Lower Scar limestone of Settle, in Yorkshire, and from which my description is 

 taken. When it so happens that, from fracture, the auriculate expansions are absent and 

 that the area is not exposed, some examples in this condition might be mistaken for 

 certain deeply sinuated specimens of P. lonr/ispinus, but the last-named shell is usually 

 more regularly vaulted and rarely geniculated to the extent observable in P. sinuafus. 

 Interiorly, both species differ in the position which the adductor muscular impressions in 

 the ventral valve occupy relative to the divaricator ones ; those in P. sinuafus being longi- 

 tudinally parallel or on a level with the divaricators, while in P. longispinus the last- 

 named, muscular scars commence under and outside of the adductor impressions, so that 

 in Sowerby's shell the four muscular scars in the ventral valve occupy a larger space than 

 in P. sinuafus, where they are all on a level or parallel to each other, and occupy a small 

 saucer-shaped space in the rostral portion of the valve. In the dorsal valve the muscular 

 and reniform impressions do not appear to differ much in detail from those of P. longispinus 

 or of the generality of other Producta, and in any case the interior markings denote with 

 certainty that P. sinuafus is a true Producfus, and could in no case be classed with 

 Lepfcena. None of the specimens or internal casts exhibited evidence of teeth, so that it 

 is probable that the valves were unarticulated, as they appear to be in all known species 

 of the genus. 



Prof. M'Coy mentions that the shell under description is rare in the Carboniferous 

 limestone of Derbyshire, and it has been recently discovered at Bower trapping, near 

 Dairy, Ayrshire, Scotland, and which I was happy to recognise among some duplicates 

 forwarded to me by Mr. Young. 



