﻿82 



DEVONIAN FAUNA. 



Under the designation Pterinea, sp., Kayser 1 figures the hinder part of a right 

 valve of a species which may, perhaps, be kindred to the present, but his figure is 

 insufficient for specific identification. It seems to differ in having much wider 

 interspaces and narrower ribs, and in not having a minor series coming in 

 between the major ribs. 



Monotis Hercynica, Beushausen, 2 differs in the shape of its anterior ear, in its 

 ribs being coarser, and its umbo more prominent. 



Pterinopecten crenicostatus, Hall, 3 and Pterinopecten suborbicularis, Hall, 4 are 

 American forms that come so near as to be local representatives or possibly even 

 local varieties of the present species. The first is distinguished by its fewer, 

 coarser, and more distant ribs, the second by its much less defined anterior ear. 



2. Ptbrinopecten Cybele, Barrande, sp. PI. VIII, fig. 9, 9 a, 10, 10 a ; PI. IX, 



fig. 1. 



1881. Avictjlopecten Cybele, Barrande. Syst. Sil. Boheme, vol. vi, pi. ccxxviii, 



figs. 2, l-io, Et. E. 



1889. — — Whidborne. Geol. Mag., dec. 3, vol. vi, p. 78. 



Description. — Left valve of moderate size, obliquely ovoid, not transverse; 

 length and breadth nearly equal. Umbo small, low, direct, rather flattened, 

 proximate, extending slightly above the hinge-line, and situated, some distance 

 in front of the middle line of the shell. Hinge-line long, straight, equal to the 

 greatest length of the shell. Anterior wing diffuse, broad, rather large ; convex 

 above and then concave as it passes insensibly into the median part of the shell. 

 Posterior wing broad, triangular, flat. Anterior margin oblique, being nearly 

 erect and slightly concave below the hinge-line, the margin being then continued 

 in a slightly convex curve over the rest of the anterior and inferior rim until the 

 infero-posterior corner, round which the curvature increases. Posterior margin 

 sigmoid, being slightly convex and oblique below and concave above. Contour 

 of surface gently and evenly convex in the central parts, concave at the junction 

 of the wings. Surface covered with about seventy or eighty smooth, rounded, 

 distant ribs, sometimes alternating and mostly extending nearly to the umbo, 

 separated by flat interspaces wider than the ribs ; the whole crossed by minute 

 threads and by ten or twelve well-marked and rather regular concentric undula- 



1 1878, Kayser, ' Abhandl. Geol. Specialk. Preuss.,' Band ii, pt. 4, p. 133, pi. xix, fig. 1. 

 ■ L884, Beushausen, ' Abhandl. Geol. Specialk. Preuss.,' Band vi, pt. 2, p. 61, pi. ii, fig. 4. 

 3 1 88 I , Ball, ' Pal. N. Y.,' vol. v, pt. 1, p. 78, pi. viii, figs. 3, 4 ; and pi. lxxxii, fig. 14. 

 1 Ibid., p. 80, pi. viii, figs. 1, 2; pi. xxiv, fig. 10; and pi. lxxxii, fig. 6. 



