152 University Geological Survey of Kansas. 



YOLDIA. 



Moeller, Kroyer's Nat. Tid., IV, p. 91, (1812). 



Yoldia subscitula. Plate XX, fig. 8. 



Lecla subscitula Meek and Hayden, Trans. Alb. Inst., iv, p. 79, (1858). 

 Yoldia subscitula f Meek, Fin. Rep. U. S. Geol. Surv. Neb., p. 205, pi. x, 

 f. 10, (1872); etc. 



Meek's description: "Shell longitudinally subovate or sub- 

 elliptic, compressed, the greatest convexity a little in advance 

 of the middle, about twice as long as high ; anterior extremity 

 wider than the other but rather narrowly rounded, the most 

 prominent point being usually slightly above the middle ; out- 

 line of base forming a broad semiovate curve, being more 

 prominent anteriorly than behind ; posterior side narrowed, its 

 margin rounding up gradually from the base, so as to meet the 

 dorsal margin at nearly right angles, sometimes faintly truncate 

 at the immediate extremity ; posterior dorsal margin compressed 

 or cuneate, and declining gradually, with a nearly straight, or 

 slightly concave outline ; anterior dorsal margin not cuneate, 

 sloping forward gradually, and a little convex in outline ; beaks 

 rather depressed or subcentral, or very little in advance of the 

 middle ; umbonal slopes without any defined ridge or angle. 

 Surface smooth, or only showing traces of \ery minute con- 

 centric striae. Length, 0.77 inch ; height, 0.37 inch ; convex- 

 ity, 0.14 inch. 



" It is with considerable doubt that I have concluded to refer 

 this shell to Y. subscitula M. and H., because the specimens from 

 Nebraska City are distinctly more compressed than the type 

 upon which that species was founded, their convexity being 

 uniformly not more than half as great proportionally. The 

 five or six individuals in the collection are constant in this 

 character, and yet show no evidences whatever of accidental 

 compression. Otherwise the two forms are very similar in their 

 general outline, but we know nothing of the internal and hinge 

 characters of the form under consideration. I strongly suspect, 

 however, that it will be found to be a distinct species, in which 

 case I would propose to call it Yoldia propinqua, from its near 

 resemblance to Y. subscitula." 



