BEEDE: NEW FOSSILS FROM THE KANSAS COAL MEASURES. 127 



Measurements: Height, 23 mm.; length, 23 mm.; convexity of 

 valve about 4 mm. 



Taken from the rock at the dam at Lawrence, Kansas. 



A specimen from the dam, at Lawrence, and shown in Figs. 6b 

 and 6c, Plate XXXII, is probably of the same species, though it 

 has a somewhat different appearance and outline. It shows the 

 beak projecting beyond the hinge and the cast of the interior shows 

 the beak to have been hollow beyond the hinge. The cast figured 

 is of both valves in place, one of which is slightly crushed. It 

 may be a distinct species, though as it is from the same horizon it 

 is probable that the difference is individual rather than specific. 



The character of the hinge and the internal markings are too poorly 

 shown in our specimens to permit of the accurate location of the 

 species. It resembles very much in appearance species of the 

 genus Posidononiya, to which it is provisionally referred, and with 

 which it agrees in its surface markings and in having a v^xy thin 

 shell. It also agrees very well in these respects with Faracyclas, 

 but that genus is not at present known from the Carboniferous. 



Posidonoraya? pertenuis, n. sp. Plate XXXII, Fig. 5. 



Shell a little larger than the previous and less oblique. Trans- 

 versely ovate in outline, very thin, quite compressed. The hinge 

 line is nearly straight and about equaling half the length of the 

 shell. The posterior? margin is somewhat truncate and nearly 

 straight; anterior extention of the hinge longer than the posterior, 

 rather flat, not separated from the shell by well defined depression. 

 The front and ventral margins regularly rounded. The shell is 

 compressed, probably most convex near the middle, beak obtuse, 

 not very prominent, protruding above the hinge line. The surface 

 is marked by concentric undulations of growth and fine, close, con- 

 centric striae. 



Measurements: Height, 40 mm.; length, 36 mm.; convexity of 

 single valve, 4 or 5 mm. 



The type specimen was taken from near the dam at Lawrence, 

 and others have been taken since from the same stratum at Cam- 

 eron's Bluff, three miles up the river. 



This species belongs to the same genus as the preceding. It has 

 some resemblance to the figure of Keyes'*, which he refers to 

 Placunopsis carbonaria, though it is very difficult to see why it should 

 be referred to that genus or species; his species may be the same 

 as the one here described. 



*GeoL Surv. Mo., v, p. 108, pi. xliii, f. ». 



