DESCRIPTIONS OF NEW SPECIES. 121 



The whole surface marked by fine revolving striae, which are more 

 distinct upon the last volution and wing ; last volution also marked by a 

 moderately strong revolving carina, which extends outward upon the wing 

 and is continued to the point of the falciform process. 



Length, sixteen millimeters; breadth across the body volution, includ- 

 ing the wing, twelve millimeters. 



This species resembles A. Americana Meek and Hay den. in general 

 form and surface markings, but it differs from that shell by its large anterior 

 sinus, the inflection of the anterior border, and the reflexion of the posterior 

 border of the wing, and also in the general shape of the wing. 



Position and locality. Sulphur Creek Group; Upper Kanab, Utah. 



Ancliura prolabiata (sp. nov.). Shell rather above medium size, sub- 

 fusiform ; spire elongated and tapering, with nearly straight sides, to a 

 point ; volutions, nine or ten, convex, the last one proportionally more en- 

 larged than the others ; suture impressed ; wing large, broad, its outer 

 border nearly straight or slightly convex, its anterior and posterior corners 

 abruptly rounded ; posterior border bearing a strong, broad, blunt process 

 about midway between the spire and the outer margin of the wing, the 

 outer margin of the process having a direction parallel with that of the 

 outer margin of the wing ; posterior border of the wing concave between 

 the outer corner and the base of the process, and also regularly and con- 

 tinuously concave from the spire to the end of the process ; anterior border 

 of the wing broadly and regularly concave to the base of the anterior canal, 

 which is apparently rather short. 



Inner lip unknown. 



Surface of the volutions of the spire marked by numerous vertical or 

 slightly oblique folds or ridges, which disappear upon the body volution 

 and wing ; these folds are crossed by numerous fine revolving raised lines, 

 which are hardly visible without the aid of a lens, except those adjacent to 

 the sutures, which are stronger ; these revolving lines are perceptible upon 

 the body volution, but are very faint upon the wing. No revolving ridge 

 passes out upon the wing from the body volution, such as is common upon 

 shells of this genus. 



Length about four and a half centimeters ; breadth, measured across 



