306 UNITED STATES GEOLOGICAL SURVEY OF THE TERRITORIES. 



of its form. Still, however, supposing our shell to he identical with B.I vin- 

 culum, of which I can scarcely have any doubts, its much larger size, propor- 

 tionally less slender form, and well-developed inner lip, would seem to forbid 

 its reference to F. Shumardii, which, notwithstanding its decidedly smaller 

 size, has the same number of volutions as our largest specimen ; while it is 

 nearly always the case that young univalves are jiroportionally less elongated 

 than the adults of the same species This latter fact strongly favors the con- 

 clusion that the typical specimen of B.\ vinculum (and not that of Fusus Shu- 

 mardii) is a young individual of the shell here under consideration. I have 

 no means of knowing whether or not the type-specimen of Fusus Shumardii 

 has internal varices* ; but it very probably has, whether specifically distinct 

 from J3. ? vinculum or not; because, from its external characters, it probably 

 belongs to the same genus, at least. Casts of our shell, however, show it to 

 possess this character as in the original typical B. 1 vinculum. 



Among foreign forms, this species may be compared with Tritonium 

 Gosauanum, Zekeli (Gast, Gosaugeb., 82, pi. 15, fig. 2), from which it differs 

 in having its body-volution less abruptly contracting below, and its vertical 

 folds, or costa?, much less distinct on the same. The Gosau species also 

 shows more indications of external varices than our shell. I believe, how- 

 ever, that it belongs to the same group. 



Locality and position. — The original type-specimen of Buccinuml vin- 

 culum came from the Great Bend of the Missouri River, Dakota, where it 

 was found in the Fort Pierre group of the Upper Missouri Cretaceous series. 

 Our figured specimens were also obtained from the same locality and bed. 



FAMILY- AFFINITIES UNDETERMINED. 



Genus CLOSTERISCUS, Meek. 

 Synon. — Fusus 1 (sp.), Hall and Meek; not Lamarck. 



jEtym. — n\uar>jp, a spindle (dimin.). 



Type. — Fusus Henuilineatus, Hall and Meek. 



Shell thin, fusiform, with spire slender and produced to a greater length 

 than the aperture and canal ; body-volution not ventricose, terminating below 

 in a canal; surface smooth, or minutely striate ; aperture rhombic; outer lip 

 broadly retreating above the middle, thin, excepting at irregular intervals, 

 where it became thickened and denticulate within, so as to leave internal 



* These comparisons are made with the published figures only of F. Shumardii, as I have uot seen 

 the original type for many years. 



