160 BRITISH CARBONIFEROUS BRACHIOPODA. 



Productus arcuarius, Be Koninck. PL XXXIV, fig. 17. 



Pboductus arcuarius, De Kon. Descript. du Animaux foss. du terrain Carb. de la 



Belgique, p. 171, pi. xii, fig. lO"''' 1843, and Mon. du 

 genre Productus, pi. iv, fig. 2. 



Spec. Char. Shell small, transversely oval ; hinge-line much shorter than the greatest 

 width of the shell. Ventral valve almost hemispherical and regularly vaulted up to a 

 certain distance or age, when it is again continued under the shape of a wide, prominent 

 border, separated from the rostral half by a groove, which, originating on either side of the 

 beak, curves round the valve. The margin is also sometimes bent up at right angles, and 

 thus forms a flattened rim all round the shell. Beak and auricular expansions small. 

 Surface ornamented by numerous radiating, thread-like striae, which become more numerous 

 by interstriation, and are here and there swollen out, giving rise to a variable number of 

 slender, tubulated spines, which are more numerous on the ear-shaped expansions. Dorsal 

 valve concave, following the curves of the ventral one, and similarly ornamented. Interior 

 unknown. Dimensions variable; a British example measured — length 5|, width 8 lines. 



Obs. This little shell does not appear very rare in the Carboniferous limestone of 

 Settle, in Yorkshire, where it was discovered for the first time in Britain by Mr. Burrow. 

 Having submitted specimens to Prof, dc Koninck, he declared them to be specifically 

 identical with those from Vise, in Belgium. The concentric groove which divides the 

 ventral valve into two portions is not, however, always so distinctly marked in the British 

 specimens that have come under my observation as in certain Belgian individuals figured 

 bv Prof, de Koninck. 



Productus carbonarius, De Koninck. PI. XXXIV, fig. 0. 



Piioductus cakbonarius, De Koiti/ick. Descrip. des Animaux t'oss. der terr. Carb. 



de la Belgique, pi. xii bi "' fig. 1, 1843, and Mon. du genre 

 Productus, pi. x, fig. 4, 181". 



— — De Verneail. Russia and Oural Mountains, pi. xvi, fig. 2, 



1845. 



— — Dav. A Mon. of the Carb. Brachiopoda of Scotland, pi. iv, 



fig. 14, 1860. 



Spec. Char. Shell of median size, about as wide as long, or slightly transverse ; 

 \ en tral valve very gibbous, evenly rounded, tin d without sinus; auriculate expansions small; 

 hinge-line nearly as wide as the greatest width of the shell. Surface ornamented with very 

 fine, thread-like, radiating striae, from which project at short intervals numerous slender 

 spines, the rib becoming thickened at the spot where the spine originates ; beak small, 

 much incurved, and covered with a few slight concentric wrinkles. Dorsal valve following 



