﻿PTERINEA. 



57 



Isocardia vetusta, Goldfuss, 1 differs from the widest variety of our shell by 

 having a blunter umbo, a staighter hinge-line, and more definite wings. 



Inoeeramus inversus, Goldfuss, 2 which is Posidonomya inversa, Geinitz, 3 has a 

 more terminal umbo, no anterior ear, and indistinct posterior radiations. 



Rutotia obtusa, de Koninck,* is much higher than long, and has more equal 

 and angular wings and a blunter umbo. 



R. obesa, de Koninck, 5 is transversely striated, and has a more obtuse umbo 

 and a more defined and higher hind winsr. 



R. ornithocephala, de Koninck, 6 has a more prominent, twisted, and sharper 

 beak, and is more oblique and not quite smooth. 



R. amygdalina, de Koninck, 7 very nearly agrees in shape with our younger 

 forms, but is striated, and has a smaller, blunter umbo and less unequal wings. 



3. Genus. — Pterinea, Goldfuss, 1826. 



This genus seems distinguished from Avicula and Actinopteria by its large 

 prominent central and lateral teeth, by its strong horizontal ligamental furrows, 

 and by the great inequality of its valves. The shell seems generally to be thick 

 and the hinge-area broad and flat. The anterior muscle-scar is moderately 

 developed and deep. 



Freeh has placed it with Actinoderma, Sandberger, in a separate sub-family, 

 which he calls Pterinseinse, while Hall ranks it with Actii copter ia under a distinct 

 family, Pterinidae. 



It finds its chief development in the Devonian period, but it is also quoted 

 from the Silurian and the Carboniferous. 



1. Pterinea bellula, Whidbome. PI. IV, fig. 11. 



1889. Pterinea bellula, Whidbome. Geol. Mag., dec. 3, vol. vi, p. 79. 



Description. — Left valve large, slightly oblique, apparently much broader 

 than long, moderately convex. Umbo small, anterior, proximate, incurved, and 



1 1834-40, Goldfuss, ' Petref. Germ.,' vol. ii. p. 284, fig. 1G0, fig. 14 



2 Ibid., vol. ii, p. 108, pi. cix, figs. 6 a, b. 



3 1853, Geinitz, ' Verst. Grauw. Sachsen,' pt. 2, p. 53, pi. xii, fig. 25 ; and pi. xiii, figs. 1. 2. 



■ 4 1885, de Koninck, ' Ann. Mus. Eoy. H. N. Belg.,' vol. ix, pt. v, p. 199, pi. xxii, figs. 6, 17. 

 5 Ibid., p. 199, pi. vii, figs. 3, 4. 



G Ibid., p. 200, pi. vii, figs. 29, 30 ; and pi. xxii, figs. 25, 29. 

 ' Ibid., p. 200, pi. xiii, figs. 24, 25, 44, 45. 

 VOL. II. 8 



