332 UNITED STATES GEOLOGICAL SURVEY OP THE TERRITORIES. 



Tanikoropsis Tiieiiiryana, M. & H. (sp.). 



Plate 39, figs. 2, a, b. 



Nalica Tuomeyana, Meek and Hayden (1856), Proceed. Acad. Nat. Sci. Philad., VIII, 270. 

 Naticopsist Tuomeyana, Meek and Hayden (1860), it., XII, 423. — Meek (1864), Smithsonian Check-List 

 N. Am. Cret. Fossils, 18. 



Shell depressed-subglobose, very strong; volutions four to four and a 

 half, convex, last, one composing most of the entire bulk, and regularly 

 rounded; suture rather deep; aperture ovate or nearly so, being a little 

 straighter on the inner side; columella with the faintest appearance of a very 

 small umbilical indentation by the side of the smooth, scarcely thickened, 

 inner lip. Surface of the upper volutions showing only the regular, distinct, 

 revolving lines and fine striaa of growth, the former of which increase regu- 

 larly in size on the body-whorl, on which the strong, vertical, or more or less 

 oblique, folds, or plications, are inclined to be angular on their crests, with 

 broad, rounded, deep depressions between. 



Length and breadth, each, about 0.88 inch. Apical angle with nearly 

 straight slopes, and a divergence of about 110°. 



This species will be at once distinguished from all of the other known 

 Upper Missouri univalves resembling it in other respects, by its thick shell 

 and distinct revolving lines, crossed on the body-volution by large, strong, 

 oblique folds, or plications; thus giving it a peculiar rough appearance. I am 

 not acquainted with any described foreign species resembling it closely 

 enough to render a comparison necessary. It seems to be very rare, as all 

 of the collections yet brought from the Far West have only afforded us a single 

 specimen. 



Locality and position. — Mouth of Judith River, on the Upper Missouri; 

 from Cretaceous beds holding a position at the horizon of the top of the Fox 

 Hills group. 



TURRITELLID/E. 

 Genus MESALIA, Gray. 



Synon.— Mesalia, Gray (1842), Synon. Moll. Brit. Mus.,61, 90; and (1847) Zool. Proceed., 155.-H. and A. 

 Adams (1856), Genera Keccut Moll., I, 35. — C'hcnu (1859), Man. Conch., I, 317 (as a 

 subgenus under TurriteUa). 



Etym. — (? Mesal, Ad., a word of barbarous origin.) 

 Type. — Cerithium nasal, Adanson. 



Shell many-whorled, short-subterete ; volutions more or less convex, and 

 spirally striated, the last one rounded below; aperture suborbicular, produced 



