AET. XX -PALEONTOLOGICAL PAPERS NO. l.-DESCPJPTIONS 

 OF UNIONIDJ] AND PHYSID.E COLLECTED BY PROFESSOR E. 

 D. COPE FROM THE JUDITH RIVER GROUP OF -MONTANA 

 TERRITORY DURING THE SUMMER OF 1876. i oC^^jo^yvuju) 



By C. a. White, M. D. 



UNIONIDiE. 



Unio PRiMiEVUS (sp. nov.). — Shell of mediiira size, broadly subovate in 

 marginal outline when adalt, but proportionally narrower when young; 

 valves moderately convex, each having an umbonal sinus or radiating 

 flattened space which ends at the ventral margin a little behind the 

 mid-length of the shell ; the sinus or flattened space is bordered poste- 

 riorly by a broad, undefined, umbonal ridge, or slight radiating promi- 

 nence; beaks situated nearly equidistant from the anterior and poste- 

 rior ends, prominent by reason of the abruptly sloping away from it of 

 both the antero- and postero-dorsal borders as well as the sides; from 

 the beaks to the postero-ventral portion of the shell the margin is 

 broadly convex ; postero-ventral margin abruptly rounded to the ventral 

 margin, and the latter broadly convex, or nearly straight along its mid- 

 length; front regularly rounded ; both cardinal and lateral teeth strong 

 and well developed. The posterior end of the lateral portion of the 

 hinge ends by a thickening and rounding of its substance upon the 

 inner or under side, instead of each lateral tooth or lamellation ending 

 thinly or sharply, as they usually do in this genus. The postero-dorsal 

 portion of the surface is marked by somewhat distant, very irregular 

 raised ridges, or sharp lines, giving the surface a corrugated aspect; all 

 the surface in front of the corrugated portion is marked only by the or- 

 dinary concentric lines of growth and the common fine radiating lines 

 observable in the substance of the shell when it has been exfoliated. 



This shell is somewhat remarkable for its broadly subovate outline 

 and the unusual character of the irregular raised lines on the postero- 

 dorsal surface. 



The peculiar character of the lateral portion of the hinge observed in 

 this species was also observed in Unio .stctvardi AVhite from the .lurassic 

 strata of Northern Utah, but it seems to be characteristic of only a few 

 species of fossil Unios, and not confined to any epoch or period. 



Length of an adult specimen G5 millimeters; height of same from 

 base to beak 49 millimeters. 



Position and locality. — Fernigiiious sandstones, at the summit of the 



