198 CRETACEOUS PERIOD. 



nitna) melanopsis. — Subulate; whorls nine, flattened on the sides; ribs 

 regular, slightly curved, about seventeen in number on the body-whorl ; 

 revolving lines distinct, unequal, about seventeen in number on the penulti- 

 mate whorl ; suture impressed, slightly waved ; aperture long, elliptical." 



Suborder TOXOGLOSSA. 



Family ADMETID^. 



Genus ADMETE Moller^ 1842. 



Subgenus ADMETOPSIS Meek, 1872. 



Admete (Admetopsis) gregaria Meek. 



Plate XVIII, fig. 5 a and h. 



Admete f gregaria Meek, 1872, Geol. Surv. Moutana, Idaho, Wyoming, and Utah, 506. 



Shell rather small, subfusiform, excluding the outer lip ; spire promi- 

 nent, tapering to a small apex; volutions six or eight, convex, abruptly 

 rounded in to the suture above ; suture well defined ; last volution moder- 

 ately inflated, its length equal to, or a little greater than, one-half the full 

 length of the shell ; aperture of moderate size, about as long as the spire, 

 narrowing posteriorly and ending anteriorly, at the base of the columella, 

 in a distinct sinus ; columella marked by two spiral folds, the larger one of 

 which blends with the truncated extremity of the columella. The other 

 fold Ls placed a little above the first and passes backward into the aperture 

 a little more obliquely ; inner lip a little thickened along its whole length ; 

 outer lip in adult shells moderately thick, its outer margin broadly rounded, 

 and its anterior margin abruptly truncated to the base of the columella. 



Surface marked by numerous, more or less strongly-elevated, longitudi- 

 nal or slightly oblique folds, of regular but gradually-increasing size, coin- 

 cident with the growth of the shell. These folds are quite distinct upon the 

 middle volutions, scarcely observable near the apex, and sometimes obsolete 

 upon the last volution, or visible only upon its posterior portion. Numer- 

 ous small, revolving, raised lines cross these folds, often not perceptible 

 between, but distinct upon, the folds, giving them a nodulose or corrugated 

 appearance. These revolving lines are always present and usually con- 

 spicuous vipon the anterior part of the last volution. 



