PRODUCTUS 165 



shorter than the greatest width of the shell. Ventral valve gently convex from the extremity 

 of the beak to the front, the lateral portions being much extended and bent downwards 

 at almost right angles to the plane of the valve ; beak and auriculatc expansions small, 

 with a ridge commencing at their extremity, extending to some distance on cither side, 

 thus dividing the visceral from the labial extensions of the valve. The surface is covered 

 with numerous threadlike, radiating striae, which increase in number by interstriation at 

 various distances from the beak, from which project a few scattered spines ; it is also 

 ornamented by many concentric, undulating wrinkles, which become larger or wider as 

 they recede from the extremity of the beak. The dorsal valve is concave, following closely 

 the curves of the opposite one, and is similarly ornamented. Interior like that of 

 other Producta. A British example measured — 



Length 10, width 9^, lines. 



Obs. This species differs from P. proboscideus, by its dorsal valve following exactly 

 the curves of the ventral one, and by the last-named valve not being prolonged in the 

 form of a cylindrical tube. It occurs in the Carboniferous limestone of Settle, in York- 

 shire, where it was found for the first time in England by Mr. Burrow, and is there 

 associated with P. proboscidens, as well as at Vise, in Belgium, the only two localities in 

 which the species has been hitherto discovered. 



Productus tessellatus, Be Koninck. PI. XXXIII, figs. 24, 25; PI. XXXIV, 



fig. 14. 



Productus muricatus, I)e Koninck. Descript. des Animaux foss. du Terr. Carb. 



de Belgique, p. 192, pi. ix, fig. 2 ; pi. 13 1,u - fig. 5 (not 



Phillips), 1843. 

 Productus tessellatus, De Koninck. Monographic du genre Productus, Memoires 



de la Soc. Royale des Sciences de Liege, vol. iv, pi. xiv, 



fig. 2, 1847. 

 — — Morris. Catalogue, p. 145, 1854. 



Spec. Char. Shell small, transversely oval, a little wider than long ; hinge-line 

 much shorter than the width of the shell. Ventral valve evenly convex and regularly 

 vaulted, without sinus ; beak small, prominent, and incurved, not projecting beyond the 

 hinge-line ; auriculate expansions very slightly developed. Surface ornamented by from 

 fifteen to twenty round, salient costae, from which project a few scattered spines, and inter- 

 sected by about as many concentric grooves ; margin bent upwards, wide, flat, or slightly 

 concave, and marked by numerous rounded, bifurcated, or trifurcated ribs, with dorsal 

 valve gently concave, and ornamented as in the ventral one. Interior unknown. Dimensions 

 variable ; two British examples have measured — 



Length 11, width 12, lines. 

 r> m 



