184 UNITED STATES GEOLOGICAL SURVEY OF THE TERRITORIES. 



that it was merely marked by moderately distinct concentric striae. It is 

 very nearly related to, and possibly not distinct from, an Upper Cretaceous 

 species we have proposed to call C. Nebrascensis, from the North Branch of 

 Platte River, near the mouth of Deer Creek, but, in the only specimen 

 seen, it seems to have a decidedly deeper and narrower pallial sinus. 



The specific name was given in honor of the late Dr. David Dale Owen, 

 cf New Harmony, Indiana, the well-known western geologist. 



Locality and position. — Mouth of Judith River; in a Cretaceous bed 

 now known to hold a position at the horizon of the Fox Hills group. 



Callista (Dosiniopsis) Ncbrasccnsis, M. & H. 



Fie. 15. Fig. 10. Fig. 17. 



Callista (Dosintopsis) Nebrascensis, M. & II. 

 Fig. 15. Left side view of exterior. 



Fig. 16. An anterior profile view of the two valves united. 

 Fig. 17. Hinge and internal view of right valve. 



Callista Nebrasccnsis, Meek and Haydeu (1856), Proceed. Acad. N. Sci. Philad., VIII, 83. 



Callista Deweyi, var. robusta, Meek and Hayden (1861), ib., XIII, 443 (not C. Deweyi, M. & H., 1856). 



Dione Xibrascaisis, Meek (1864), Smithsonian Check-List N. Am. Cret. Fossils, 13. 



Shell attaining a medium size, rather thick, suborbicular, or transversely 

 a little oval, the height of large specimens being generally about seven-eighths 

 the length ; valves moderately and evenly convex ; anterior margin somewhat 

 narrowly rounded near the middle, and thence rounding regularly into the 

 ventral outline, which forms a broad, regular, semi-oval curve; posterior mar- 

 gin rather more broadly rounded than the anterior; dorsal border sloping 

 from the beaks, the anterior slope being more abrupt and concave, and the 

 posterior longer and convex in outline ; lunule subovatc, and a little impressed, 

 with sometimes a faint marginal line; escutcheon long, lanceolate, and rather 

 impressed; ligament long, narrow, somewhat deeply seated, or scarcely as 

 prominent as the lateral margins of the escutcheon; beaks moderately promi- 

 nent, rather oblique, and subcentral, or nearer the middle than the anterior 

 margin; surface concentrically striated; muscular impressions shallow, ovate, 



