250 UNITED STATES GEOLOGICAL SURVEY OF THE TERRITORIES. 



Glycimeris occidental! s, M. & H. 



Plate 39, figs. 9, a, b. 

 Panopma qccidentalis, Meek and Hayden (1856), Proceed. Acad. Nat. Sci. Philad., VIII, 270. 



Shell transversely suhovate, or oblong, moderately gibbous ; anterior 

 end narrowly rounded ; posterior end broader, subtruncate, and distinctly 

 gaping; base straight along the middle, rounding up abruptly behind, and 

 more gradually in front; dorsum in Front of the beaks nearly straight, and 

 declining forward, and horizontal, or but slightly declining behind them ; 

 beaks small, rather depressed, somewhat incurved at right angles to the 

 hinge, located a little in advance of the middle. Surface ornamented by 

 small, irregular, concentric wrinkles, which are most distinct in the region 

 of the umbopes. 



The only specimen of this species yet seen, has the outer layer of the 

 shell partly exfoliated, and is not in a condition to have preserved fine surface- 

 markings, if they ever existed. Part of the posterior side and base are also 

 broken away ; consequently, it is possilde that, when perfect specimens air 

 obtained, it may be found necessary to modify the foregoing description 

 in some respects, especially in regard to the form of the adult shell. The 

 curves of the lines of growth, however, show that young individuals, when 

 about one inch in length, agreed in form with the above description. 



Not having seen the, hinge and interior of this shell, it has been referred 

 to the genus Glycimeris from external characters only. It may ho congen- 

 eric with sonic of the forms included in the genus Myopsh, Agassi/., 1S45. 



As near as can be determined from our imperfect specimen, it must have 

 been, when entire, about 3.50 inches in length, 2 inches in height, and about 

 1.42 inches in convexity. 



Locality and position. — Mouth of Judith River on the Missouri, in beds 

 holding a position at the horizon of the top of the Fox Hills group. 



SOLENIDiE. 



Genus PHARELLA, Gray. 



Synon.—Pharella, Gray (lK r >4), Ann. and Mag. N. H., V, 24 ( 2d ser.).— H. and A. Adams (1854), Geu. Recent 

 Moll., II, 34:!.— Chenu (1862), Man. Conch., II, 22. 



Solen (sp.), of many authors ; not of Liuiucns. 



Etym. — Pliarits (dimin.). 



Type. — Pharella Javanica, Linn. (sp.). 



Shell much elongated transversely, suhcylindrical, or somewhat com- 

 pressed, with both ends rounded and gaping; surface covered with an oliva- 



