SILURIAN MOLLUSCA. 195 



Traces of two fine internal ridges diverging from the beak of 

 the flat valve where the wings join the body of the shell (resem- 

 bling those of Pecten). The specific name was suggested by 

 Mr. Salter for this species, if it should prove new, in honour of 

 one who has diligently collected these remarkable fossils, and the 

 others occurring near Kendal. 



Very abundant in the greenish quartzite (Upper Ludlow rock) 

 of Benson Knot, Kendal, Westmoreland. 



{Col. University of Cambridge.) 



Pterinea asperula (M'Coy). 



Sp. Char. Obliquely ovate, body of the shell evenly convex, 

 abruptly defined from the anterior and posterior sides ; beak 

 gibbous ; anterior wing rounded, less than half the length of 

 the posterior wing, which is flat, acutely pointed and extending 

 a little beyond the shell, its posterior margin concave ; pos- 

 terior end of the shell broadly rounded; entire surface 

 radiated with nearly equal rough (obscurely tuberculated) 

 ridges separated by flat spaces rather greater than their dia- 

 meter in width (six ridges in one line at margin) ; these ridges 

 are crossed on the body of the shell by fine wrinkles of growth 

 which on the wing and towards the beak become sharp defi- 

 nite strise parallel with the margin ; width from beak to mar- 

 gin 2^ lines, length from beak to posterior end Z~ lines, width 

 of posterior wing from angle to side of shell 1^ line. 



Common in the black shale of Builth Bridge, Radnorshire. 

 {Col. University of Cambridge.) 



Pterinea Mans (M'Coy). 



Sp. Char. Rotundato-quadrate, slightly oblique, moderately gib- 

 bous, most so one-third the length from the beaks, which are 

 one-third the length of the hinge-line from the anterior end ; 

 anterior side large, defined by a deep hollow extending nearly 

 at right angles with the hinge-line from before the beak to 

 the ventral margin, in which it produces a slight sinus ; in 

 front of this it is convex, and then nearer the slightly acute 

 cardinal angle another smaller shallow sinus extends from the 

 margin towards the beak ; posterior wing broad, compressed, 

 not abruptly defined from the body of the shell, slightly acute, 

 and scarcely extending beyond the posterior end of the body 

 of the shell which is obtusely rounded ; ventral margin nearly 

 horizontal, slightly convex; surface with close fine equal thread- 

 like radiations, interrupted by slightly irregular concentric 

 imbrications about half a line apart. Width from beak to 

 middle of ventral margin Q\ lines, length of hinge-fine 9 lines. 



N 2 



