INVERTEBRATE PALAEONTOLOGY. 343 



genus, this shell differs in having a proportionally larger body-whorl, shorter 

 spire, and fewer whorls; its revolving lines are also smaller and more numer- 

 ous. I am not acquainted with any species with which it is apt to be 

 confounded. 



Locality and position. — Morgan River; from the Fox Hills group, or 

 No. 5 of the Nebraska Cretaceous series. 



MURICIDiE. 



Genus PYRIFUSUS, Conrad. 



Synon. — Fusus (sp.) of authors, but not of Lamarck, as properly restricted. 



Pyrifusus, Conrad (1858), Jour. Acad. Nat. Sci. Philad. (n. s.), 332.— Meek (1864), Sniithsouinu 



Check-List N. Ain. Cret. Fossils, 22. 

 ? SeptuneUa, Meek (1SG4), ii.,38 (uot Neptunella, Gray * * which is = Cabastana, Bolten, 1789, 

 and Aquillus, Montf., 1810). 



Etytn. — Pyrula and Fusus. 



Type. — Pyrifusus subdensata, Conrad. 



Shell varying from subpyriform to short-fusiform ; spire one- to three- 

 fifths the length of the aperture and canal, not papillate at the apex; body- 

 volution rather ventricose, and prominent, or obtusely subangrdar around the 

 upper third, dorso-ventrally compressed, or more generally rounded, tapering 

 below into a nearly straight, moderately-produced canal ; aperture rhombic- 

 subovate in outline, being angular, but not notched or canaliculate above, and 

 tapering downward ; outer lip thin, sometimes broadly sinuous above the 

 middle; columella solid, gently arcuate along the middle, nearly straight, and 

 without twist below, sometimes more or less flattened, but always without 

 the slightest umbilical ridge, and at least typically imperforate; inner lip 

 smooth, and closely attached to the columella and body-volution ; surface 

 with vertical, sometimes node-like, folds, around the most convex part of the 

 volutions, and revolving striae, or small ridges. 



The foregoing diagnosis is drawn up so as to include, along with Mr. 

 Conrad's typical form, a group of apparently congeneric Upper Missouri Cre- 

 taceous species, that still seem to differ in some of their characters. I only 

 know Mr. Conrad's type from his figures and description ; but, on sending 

 him some of our specimens of these shells several years back, he wrote that 

 he thought they might go into his genus Pyrifusus. Although not entirely 

 satisfied with this arrangement, having elsewhere adopted it by referring our 

 species to that genus, I prefer not to remove them from all connection with 

 the same, at least until their relations can be more satisfactorily settled; and, 



