(STANTON.) LUCINID^E. 97 



probably from about the same horizon, that was found near Canyon city, 

 Colorado. 



The specimen from Morrison is a part of the thick outer layer of the 

 lower valve. It shows the characteristic structure 01 Badiolites, con- 

 sisting of large prismatic cells arranged in layers parallel with the 

 upper surface of the shell, and the surface of each layer showing im- 

 pressions of a few slender, branched, radiating ridges on one side and 

 corresponding furrows on the other. A little of the outer surface of 

 the shell is preserved, showing narrow longitudinal ridges and grooves 

 each about a millimeter wide. The individual to which this fragment 

 belonged must have been 6 or 8 inches in diameter. The shell sub- 

 stance is over 2 inches thick. 



Compared with Badiolites austinensis Roeiner, which occurs in the 

 equivalent of the Colorado formation in Texas, this specimen seems to 

 have narrower ridges and grooves on the outer surface, while the pris- 

 matic cells of the thick shell are larger. It is doubtful, however, 

 whether these differences are of specific importance, and I think it 

 probable that better material will show that the Colorado specimens 

 b along to B. austinensis. 



' Large specimens of u Hippurites " probably belonging to this genus 

 have been reported from the Niobrara beds of Kansas. 



LUCINID^E. 

 Genus LUC IN A Bruguiere. 



LUCINA SUBUNDATA H. & M. 



PL xxii, Figs. 5 and 6. 



Lucina subundata Hall and Meek, 1856, Mem. Am. Acad. Arts and Sci., vol. v (n. s.) 

 PL 1, Fig. 6; White, 1876, U. S. Geog. & Geol. Sur. West 100th Meridian, vol. i\, 

 p. 184, PI. 18, Fig. 12a ; Meek, 1876, U. S. Geol. Sur. Terr., vol. ix, p. 133, PI. 17, 

 Figs. 2a, b,c, d, e; Whitfield, 1880, Geol. Black Hills of Dakota, p. 411, PI. 11, 

 Figs. 17 and 18. 



The following is Meek's description : 



"Shell small, subcircular, compressed, very thin; anterior side 

 broadly rounded; basal margin semiovate, the most prominent part 

 being toward the front, more or less contracted behind, smooth within; 

 posterior side narrower than the other 5 and usually subtruncate at the 

 extremity; dorsal margin concave in outline just before and convex 

 just behind the beaks, which are rather prominent, pointed, and nearly 

 central. Surface ornamented by small concentric undulations and very 

 small parallel striae, which are sometimes crossed by obscure traces of 

 very fine, nearly obsolete, radiating striae. 



" Length, 0.42 inch; height, 0.32 inch; convexity, 0.12 inch. 



" This little shell evidently varies much in form, some specimens 

 Bull. 106 7 



