128 University Geological Survey of Kansas. 



Limopteria marian. Plate XVI, figs. 5-5c. 



Monnpteria marian White, Prelim. Rep. Inv. Foss., p. 22, (1874); U. S 

 Geog. Surv. West 100 Mer., iv, p. 151, pi. xi, ff. 4a-c, (1877). 



White's description (with additions): "Shell of moderate 

 size, slender, nearly or quite equivalve, narrow and much ex- 

 tended posteriorly, the curvature being much the greater in 

 the anterior half of the shell, the posterior half being nearly 

 straight ; body of the shell gradually tapering to near the pos- 

 terior end, which is abruptly rounded ; a more or less promi- 

 nent ridge, which is sometimes in part raised as a distinct 

 carina, extends along the middle of the body of each valve 

 from the beak to the posterior end ; from this carina, or angle, 

 the sides slope abruptly to both the inferior and upper borders, 

 so that a cross-section of the shell behind the ear would have a 

 rhomboidal outline ; beaks moderately prominent, separate ; 

 hinge equal in length to about one-half the full length of the 

 shell, and its direction is nearly parallel with the posterior 

 half of the body; posterior wing well developed, not sharply 

 defined* from the body by an auricular furrow ; its cardinal 

 portion narrow and moderately extended ; anterior ear obso- 

 lete ; lunule moderately large and deep, the borders of which 

 are slightly prominent laterally, but its margins sharply 

 rounded inward. Surface smooth in aspect, but it is marked 

 by very numerous fine lines of growth. Length, from the front 

 to the posterior extremity, about 4 cm. ; height, from the base 

 to hinge margin, 18 mm. ; average width of the body of the 

 shell, about 1 cm." 



We have a left valve, probably of a large specimen of this 

 species, showing part of the muscular impressions. The ad- 

 ductor is located behind the umbonal ridge, just above and in 

 front of the marginal sinus formed by the ear and the body of 

 the shell. From the lower side of the impressions a slight line 

 runs directly forward across the umbonal ridge, then turns 

 abruptly and runs toward the anterior end of the lunule, but 

 fades out at about two-thirds of the distance. In front of the 

 scar, and crossing the front edge of it, is a line at right angles 

 to the first, beginning a little above the scar and fading out 



