308 UNITED STATES GEOLOGICAL SURVEY OF THE TERRITORIES. 



Closteriscus tennilineatns, H. & M. (sp.). 



Plate 19, figs. 10, a, b, and 9 c. 



Fusus^ tenitilineatus, Hall and Meek (185fi), Mem. Am. Acad. Arts and Sei. Boston, V (n. s.), 392, pi, iii, fig. 



9.— Gabb (1861),Synop. Moll, Cret. Form., 53. 

 Tritoiiifusus? lenuilineatus, Meek (1864), Smithsonian Check-List N. Am. Cret. Fossils, 22. 



Shell elongate-fusiform ; spire acutely elevated ; volutions about seven, 

 very slightly convex, last one compressed above and contracting abruptly 

 into the beak below; suture distinct; surface appearing to the eye smooth, 

 or even polished, but, by the aid of a magnifier, seen to be marked by 

 extremely minute, obscure lines of growth, and equally small, but slightly more 

 regular, minutely flexuous, revolving striae, which become a little larger near 

 the upper margin of volutions, and still stronger and much more oblique 

 near the base of the last turn ; aperture rhombic-oval, being rather acutely 

 angular above, and contracting rapidly on the outer side into the canal below; 

 length of canal unknown. 



Length of the largest specimen known, exclusive of the canal, about 2 

 inches; breadth, about 0.70 inch ; slopes of spire nearly straight ; divergence 

 of same 30°. 



No specimens of this species have yet been found with the beak and 

 the apex of the spire unbroken. From the general appearance of the broken 

 beak, and the base of the body-volution, it is probable, however, that the 

 former was rather shorter and a little more curved than represented by the 

 outline-restoration of our figures; which also have the suture represented 

 slightly too oblique, and the lines of growth too strong. Generally, the sur- 

 face appears smoothly polished to the unassisted eye; but, under a magnifier, 

 the minute lines of growth and revolving striaj are seen nearly as in the 

 enlargement, numbered by mistake 9c, instead of 10c, on our plate 19. 



The denticulate internal varices, or, more properly, their impressions, are 

 distinctly seen on casts of the interior, as shown in figure 9, a, plate iii, of the 

 memoir in which the species was originally described. Since our figures 

 were drawn, I have also picked off a piece of the shell at about the same posi- 

 tion in our figured specimen, and found that it shows this character equally 

 well developed. 



As already intimated, Pterodontal terebralis, from the East Indian Cre- 

 taceous rocks, more nearly resembles this shell than any other with which 

 I am acquainted. Its volutions, however, are more flattened than in the 

 species here under consideration, and its last one differs in being sub- 



