130 University Geological Survey of Kansas. 



Range and distribution : Upper Coal Measures ; Kansas City, 

 Turner, Lawrence. 



The short, gibbous shell with a moderately long spine sepa- 

 rates this species from the rest of the genus. 



Limopteria alata. Plate V, fig. 5. 



Monopteria gibbosa alata Beede, Kans. Univ. Quart., vn, p. 189, f. 5, 



(1898). 



Shell small, extremely thin, laterally compressed; beak ex- 

 tending a trifle beyond the hinge line, prominent on account of 

 the lunule, but not much elevated, and placed well back for a 

 member of this genus ; umbonal ridge less prominent than in any 

 other species of the genus and less curved. Posterior ear very 

 greatly developed, about equaling the entire body of the shell 

 in area. Antero-dorsal margin sinuate on account of the turn- 

 ing down of the margin to form the lunule ; anterior margin 

 circular nearly to the postero-ventral extremity of the shell, 

 which is acute ; the posterior margin consists of a broad, shal- 

 low sinus, extending from the postero-ventral end to the point 

 of the ear, which is apparently rounded and obtuse. The ear is 

 not separated from the shell by a distinct depression, but slopes 

 gradually from the umbonal swell, save at the extreme lower 

 edge, where the depression is more abrupt. Very fine con- 

 centric lines of growth are visible, all of which pass around the 

 shell with a double curve to the ear, where they again curve 

 backward, and then forward to the hinge line. Length, 20 

 mm. ; depth, 18 mm. ; convexity of single valve, a trifle less 

 than 4 mm. 



Range and distribution: Upper Coal Measures; Turner, 

 Law r rence. 



This shell differs from L. gibbosa M. and W., to which it is 

 most closely related in some respects, in being much less gib- 

 bous, the ear much larger and more obtuse, antero dorsal out- 

 line more sinuous, umbonal ridge more nearly straight and less 

 prominent, beak placed farther back, and the depression sepa- 

 rating the ear from the umbonal ridge more shallow. 



