JNVvr Sperirs of Juj.ssi/s frmii (lliia. 'Z'i'-\ 



olongcite, and cyliudrically oval, the cai'diual aud basal luargius parallel and 

 very slightly curved^ and the exlreiiiities very nearly equally rounded ; 

 beaks small, inroUed, barelj^ projecting above the cardinal line, and situated 

 at about one-fourth of the entire length from the anterior end. Body of the 

 shell very evenly and highly rounded from the cardinal to the basel margins, 

 and almost as convex posteriori}- as in front. Umbonal ridge scarcely per- 

 ceptible, and the umbonal slope convex; escutcheon and lunule not defined; 

 anterior slope abruptlj' rounded. Surface of the shell marked b}' faint con- 

 centric undulations of unequal strength, but most strongly marked on the 

 posterior end and on the umbonal slope. 



The evenly convex and regularly cylindrical form of the shell, 

 together with the inconspicuous beaks and the equal-sized ante-- 

 rior and posterior extreniiti'es, are distinguishing features of the 

 species. The shell shows evidence in its form and curvature, in 

 a profile view, of having been slightly gaping behind. 



Formation and Locality. — In limestone of the age of the 

 Chester group of Illinois, at Newtonville, Ohio. 



GASTEROPODA. 



Naticopsis zic-zac, n. sp. 



Pal. O., Vol. Ill, Plate 10, Figs. 15 and 16. 



Shell small, the greatest diameter of the body-volution, in the only indi- 

 vidual seen, being about nine-sixteenths of an inch; and the entire vertical 

 height of the shell only half an inch. The shell is very obliquely ovate 

 in form, and consists of about two and a half ventricose volutions, 

 which increase somewhat rapidlj^ in size to the last one, which forms nearly 

 the entire bulk of the shell. The surface of .the shell is ornamented by a 

 series of strong and raised transverse lines, which, on the upper volutions, 

 are simple as far as the suture below, and are directed strongly backward 

 in their passage ; but on the body-volution they appear more distant and 

 conspicuous, and o,re directed strongly backward in their passage for about 

 one-third the vertical diameter of the volution, where they are bent for- 

 ward at an acute angle, and after continuing for a distance nearly equal 

 to their length above, are again bent backward. Across the midde of the 

 volution, they make two or more zig-zagging bends in vertical lines, forming 

 a revolving band of vertical ridges on the peripheiy; below this band, the 

 lines are directed forward obliquely, running nearly parallel to the base of 

 the shell. 



The peculiarity of this shell consists entirely in the structure 

 of the surface ornameutatioii, as the general form of the species 



L 



