386 UNITED STATES GEOLOGICAL SURVEY OF THE TERRITORIES. 



between the angle of the volutions and the suture above; surface marked by 

 fine but distinct lines of growth, which are crossed by numerous, rather 

 small Thread-like, revolving lines. 



Length, 1.09 inches; breadth, 0.55 inch; length of aperture and canal, 

 0.70 inch; breadth of aperture, 0.24 inch; slopes of spire nearly straight, 

 with a divergence of about 42° in adult examples. 



I am not quite sure thai tins shell falls strictly within the subgenus 

 Surcula; though it seems to agree more nearly with that than any of the 

 other established sections of the genus. It has not the elongate-fusiform 

 outline and narrow labial slit seen in Tunis proper; and, although most of 

 the specimens seem to have the inner lip obsolete, as in Surcula, some have 

 it pretty well developed, but not naturally as distinct as represented in our 

 figure 7, a, in which it is too strongly apparent on account of the weathering- 

 auay of the surface of the body-volution by its side. Specimens with the 

 outer lip broken away, and the lines of growth obliterated by weathering, 

 would not be suspected to have had a posterior labial sinus, as in this and the 

 allied genera; and it was from having at first only seen specimens in that 

 condition that this shell was originally referred to the genus Fusus. Unfor- 

 tunately, none of the figures of this species on plate 31 have the curves of 

 the lines of growth properly delineated, as they would convey the impression 

 that the deepest part of the labial sinus is coincident with the most promi- 

 nent part- of each volution, instead of farther up between this and the suture, 

 as correctly represented by the annexed wood-cut. This want of the proper 

 curve of the lines of growth in the figures of this species on plate 31, makes 

 the shell more nearly resemble Neptunella Newberryi, as represented on the 

 same plate, than is natural. The foregoing wood-cut is intended to correct 

 this defect in the figures on the plate. 



Locality and position. — Moreau River, Dakota ; from the Fox Hills 

 group of the Upper Missouri Cretaceous series. 



Till'i'is (Surcula)l II b f /. i . Meek. 



Shell elongate-conical (or fusiform), thin; spire much produced and 

 turreted ; volutions about seven, distinctly convex, or subangular' around the 

 middle, and flattened or concave with an outward slope above the angle, and 

 convex below; last one not larger than the regulai enlargement of the others 

 from the apex, each provided with about thirteen prominences or little 



