Logan ] The Invertebrates, Niobrara Group. 487 



lar, and generally becoming rather abruptly smaller on the urn- 

 bones, where their curves indicate the greater obliquity of the 

 young shell. Height of a medium-sized specimen, about four 

 and fifty-hundredths inches ; length of same, four and thirty - 

 hundredths inches ; convexity of right valve, about two and 

 fifty-hundredths inches." 



This species is found somewhat abundant in the uppermost 

 Fort Hays limestone of the Niobrara Cretaceous. Should Hap- 

 loscapha be made a subgenus of Inoceramus , as I have sug- 

 gested, the thickness of its test and the depths of its undulations 

 would place this species under that subgenus. 



Inocercunus simpsonii Meek. Plate xcvu. 



Inoceramus simpsonii Meek, 1860, Proc. Acad. Nat. Sci. Phil., p. 312; 1876, 

 Simpson's Exp. across Great Basin of Utah, p. 360, pi. iv; 1877, U. S. 

 Geol. Expl. 10th Par., vol. iv, pt. 1, p. 112, pi. xin, f. 4; Whitfield, 1880, 

 Geol. Black Hills of Dakota, p. 395, pi. vin, f. 1; Stanton, 1893, Bull. U. S. 

 Geol. Surv. No. 106, p. 79. pi. xn, f. 1. 



Meek's description: "Shell (right valve) attaining a rather 

 large size, transversely oval suboblong, gibbous., the greater con- 

 vexity being in the antero-central region, cuneate posteriorly ; 

 length nearly twice the height ; anterior end very short and 

 rounded from the beaks ; base forming a long, semielliptic 

 curve, most prominent near the middle and somewhat straight- 

 ened, or even sinuous, posteriorly ; hinge long, straight, and 

 ranging parallel to the longer axis of the shell ; posterior mar- 

 gin subtruncated, with a slight backward slope above, and 

 forming an oblique curve into the posterior basal margin ; 

 beaks depressed so as to extend a little above the hinge line, 

 incurved, and placed nearly over the anterior margin. Surface 

 ornamented with moderately distinct regular, concentric undu- 

 lations and lines of growth. Length, eight and ten-hundredths 

 inches ; height, about four and thirty -hundredths inches ; con- 

 vexity of right valve, nearly two inches." 



This form is found in the Fort Hays limestone of the Nio- 

 brara formation. The species is not abundant in the Kansas 

 area. 



