INVERTEBRATE PALEONTOLOGY. ;U9 



The canal of our specimen being imperfect at the extremity, we have no 

 means of determining its comparative length ; though the remaining portion 

 shows that it ranges more nearly in a line with the central axis of the spire 

 than that of P. Newbemji. The edge of the outer lip is likewise broken 

 away, hut the curve of the lines of growth indicates that it was prominent a 

 little below the middle, and broadly retreating or sinuous above and at the 

 base, as in the other species of the subgenus. 



Locality and position. — Yellowstone River, 150 miles above its mouth; 

 from a bed composed of a blending of the Fort Pierre and Fox Hills groups, 

 or formations Nos. 4 and 5 of the Upper Missouri Cretaceous series. 



BUCCINID^E. 



? Genus PSEUEOBUCCINUM, M. & H. 



Synon. — Bucvinum, and Bullia ? (sp.) uf some, but not as properly understood. 



Pseitdobuccinum, Meek and Hayden' (1856), Proceed. Acad. Nat. Sci. Philad., VIII, 67. — Meek 

 (1867), Smithsonian Check-List N. Am. Cret. Fossils, 22.— Stoliczka (1868), Pala-out. 

 Indica, II, 142. 



Etijm. — ipevdog, false ; Buccinum." 



Type. — Buccinuml Nebrascensc, Meek and Hayden. 



Shell oval, thin, ventricose ; spire very short; body-volution large, not 

 produced below; aperture large, terminating below in a rounded sinus; outer 

 lip thin and simple ; inner lip very thin, smooth, and closely and rather broadly 

 folded upon the imperforate umbilical region and body-volution above, so as 

 to form, with a low revolving umbilical ridge, a kind of profoundly arcuate, 

 strongly-spiral, false columella; surface with more or less distinct revolving 

 lines and furrows. 



One of the most marked features of this type is its entire want of a 

 proper columella, which is merely represented by the very strongly spirally- 

 ascending, inner folded edge of the thin, inner lip, as in Bulla. It has, how- 

 ever, a low, spiral umbilical ridge, passing around up under the inner lip, and 

 terminating below at the sinus at the base of the aperture This absence of 

 a columella, the deeply arcuate and spiral character of its thin inner lip, and 

 the thinness and general form of the shell, at once distinguish this genus 

 from Buccinum, as now generally restricted. It much more nearly resembles, 

 in form and some other characters, Sulcobucci/iuin, d"Orbigny, apparently 

 synonymous with Pseudoliva, Swainson ; but its much thinner shell, want of a 



* Hybrid names like this are objectionable ; but custom seems to have sanctioned their use. 



