stanton.] AVICULTD^E. 85 



rhombic outline of this species, will readily distinguish it from all the 

 other known forms of the genus in our rocks; and I know of no foreign 

 species nearly enough related to it to render a comparison necessary. 

 Both of its valves are quite convex, but the left one is rather decidedly 

 more so than the right. 



f " One of the specimens of the right valve has its beak so nearly ter- 

 minal and its anterior margin below it so straightened in outline as to 

 present much the appearance of a typical Inoceramus ; but as the others, 

 as well as the left valve we have figured, have the anterior margin 

 more prominent, it is probable that the straightness of the anterior 

 outline in the single specimen mentioned may be, to some extent, due 

 to accidental distortion. 



u Locality and position. — Chippewa point on the Missouri, near Fort 

 Benton; from the Fort Benton group of the upper Missouri Cretaceous 

 series. Collected by Lieut. Mullan." 



Inoceramus deformis Meek. 



PI. xiv, Fig. 1; PI. xv, Figs. 1 and 2. 



Inoceramus deformis Meek, 1871, Ann. Rept. U. S. Geol. Sur. Terr, for 1870, p. 296. 



Haploseapha capax Conrad, 1874, Ann. Rept. U. S. Geol. Sur. Terr, for 1873, p. 456. 



f Haploseapha grandis and Haploseapha eccentrica Conrad, 1875, U. S. Geol. Sur. Terr., 

 vol. ii, pp. 23 and 24, Pis. 6Q and 67. 



Inoceramus deformis White, 1876, U. S. Geog. and Geol. Sur. West one hundredth Me- 

 ridian, vol. iv, p. 179, PI. 15, Figs, la and b. 



Inoceramus deformis Meek, 1877, U. S. Geol. Expl. Fortieth parallel, vol. IV. pt. 1, p. 

 146, PI. 14, Figs. 4 and 4a. 



Inoceramus f Hall, 1845, Fremont's Rept. Expl. Rocky Mts., p. 310, PI. 4, Fig. 2. 



The following is Meek's description: 



" Shell attaining a rather large size, obliquely ovate, and rather com- 

 pressed in young examples, but more rounded, gibbous, and irregular, 

 as well as much less oblique, in adult specimens; more or less inequi- 

 valve, but never very decidedly so ; posterior and basal margins rounded ; 

 the latter curving up more gradually and obliquely to the short anterior 

 margin; hinge short and usually not very oblique; beaks moderately 

 prominent, and placed between the middle and anterior margin; neither 

 greatly more elevated than the other. Surface ornamented with large, 

 strong, concentric undulations, which are sometimes moderately regu- 

 lar, but often very irregular, and generally becoming rather abruptly 

 smaller on the umbones, where their curves indicate the greater obliquity 

 of the young shell. 



" Height of a medium-sized specimen, about 4.50 inches; length of 

 same, 4.30 inches; convexity of right valve, about 2.50 inches. 



" I have frequently had under examination, during the last twelve 

 years, specimens of this shell, without being able to identify them with 

 any described species. Nearly all of the explorers who have visited 

 the eastern slope of the Eocky mountains between the south branch 



