PHTHONIA. 85 



unequal growtb-ridges. Anterior muscle- scar apparently large, and occupying the 

 anterior corner. Posterior muscle-scar large, circular, and indistinct, and situated 

 below the end of hinge-line on the posterior slope. Escutcheon very long, 

 narrow, and apparently concave and defined. 



Size. — Height 16 mm., length 52 mm., depth of the closed shell 12 mm. 



Locality. — There is a specimen in the Mantell Collection in the British Museum 

 without a locality, but resembling in the mineral character the fossils of the 

 Marwood Cucullasa beds. 



BemarJcs. — The only specimen of this shell, though very remarkable in form, 

 is so badly preserved that it is very difficult to say what it is. The hind margin 

 is gaping, but the front is so much worn away that its true shape is doubtful. It 

 appears to me very closely to resemble the figure which Beushausen gives in the 

 text of his latest work as the undistorted form of Goldfuss's Sanguinolaria 

 soleniformis. This, as far as can be judged, chiefly differs from ours in being 

 slightly shorter, and slightly less concave in the post-umbonal slope, and in having 

 a rather longer front margin ; differences probably due to the German fossil 

 having the shell. Whether Beushausen is right in identifying his shell with 

 Goldfuss's, which is totally different in appearance, I have no means of judging, but 

 if he is, it seems clear that our fossil may also be referred to it. 



Beushausen places his shell under Sphenotus, with which it appears agreeable 

 except in its extreme length. Our specimen has so much the appearance of 

 straight-hinged species of Hall's genus Cimitaria (regarded by Beushausen as a 

 synonym of Leptodomus, to which it is at all events allied), that it is quite 

 possible it may prove to belong to it, but that cannot be ascertained till a specimen 

 showing the true shape of its front side be found. 



5. Genus — Phthonia, Eall, 1870. 

 1. Phthonia, sp. Plate IX, fig. 19. 



? 1S95. Phthonia, cf. cylindeica, Kay&er. Ann. Soc. Geol. Belg., vol. xxii, p. 201, 



pi. i, fig. 9. 



Description. — Shell small, convex, extremely transverse (umbo and anterior 

 ]3arts unknown). Upper and inferior margins very long, straight, and nearly 

 parallel. Posterior margin roundly and evenly convex. Coutour of back straight 

 horizontally, roundly convex vertically. Surface with a few unequal, indistinct, 

 transverse stride. 



Size. — Length more than 17 mm., height G mm., depth of valve 2 mm. 



