146 PALEONTOLOGY. 



Inoceeamus defoemis, Meek. 



Plate 14, ligs. 4, 4 a. 



Inoceranms ?, Hall (1845), in Gen. Frdmont's Eeport Expl. Eocky Mts., 309, pi. 



Iv, fig. 2. 

 Inoceramus deformis (1872), Hayden's Second Ann. Eeport U. S. Geol. Survey of the 



Territories, 296.— White (1876), Palseout. Wheeler's Survey, 179, pi. xv, figs. 



1 ffl, &. 

 Comijare Saploscapha capax, Conrad (1874), in Hayden's Ann. Geol. Eeport for 1873, 



456; also H. grandis, Conrad (1875), in Cope's Eeport on the Vertebrates of 



Hayden's Survey, 23, pi. Ivi. 



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 inequivalve, 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 the anterior margin ; neither greatly more elevated 

 than the other. Surface ornamented with large, strong, concentric undula- 

 tions, which are sometimes moderately regular, 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 Rocky Mountains between the south branch of Platte River and New 

 Mexico have brought in specimens of it, but almost always in a distorted 

 or broken condition. Its distortion, however, is evidently not always due 

 to accident, since it often resulted from one of the depressions between two 

 of the undulations being so much larger and deeper than the others, as to 

 give the valves a remarkably constricted appearance. In other cases, it 

 resulted, in part at least, from the great irregularity in the size of the undu- 

 lations themselves. Although it is often found distorted in general form by 

 accidental pressure, it was evidently also naturally quite variable in out- 

 line, particularly in convexity. 



