PALEONTOLOGY. 477 



Formation and Locality.— -In the Maxville limestone, Chester group, 

 at Newtonville, and near Maxville, Ohio. Collected by Prof. Andrews. 



Genus NATICOPSIS McCoy. 



NATICOPSIS ZICZAC. 



Plate X, figs. 15 and 16. 



Naticopsis zkzac Whitf., Ann. Sci., 1882, p. 223. 



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

 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 rapidly 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 are directed strongly backward in their passage for about one-third 

 the vertical diameter of the volution, where they are bent forward at an acute angje, 

 and after continuing for a distance nearly equal to their length above, are again bent 

 backward. Across the middle of the volution, they make two or more zig-zagging 

 bends in vertical lines, forming a revolving band of vertical ridges on the periphery; 

 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 ornamentation, as the general form of the species is similar to 

 that of many others, but the peculiar zig-zag feature of the ornamenting 

 ridges will at once distinguish it from all other described species. Sev- 

 eral ornamented forms of the genus are known from the Coal Measures, 

 but their markings consist of nodes, either promiscuously scattered or 

 arranged in patterns. 



Formation a?id Locality. — In the limestone of the age of the St. 

 Louis and Chester beds of Illinois (Maxville limestone), at Newtonville, 

 Ohio. 



Genus HOLOPEA Hall. 

 Holopea Newtonensis. 

 Plate X, fig. 12. 

 Holopea Newtonensis Whitf., Ann. N. Y. Acad. Sci., 1882, p. 224. 



Shell of medium size, ovate in outline and ventricose, with a moderately 

 elevated spire and extremely ventricose volutions, which increase very rapidly in 

 bulk from the apex. Volutions three and a half to four in number, with strongly 

 rounded surfaces and moderate sutures. Apical angle about seventy degrees. Aper- 

 ture broad ovate, modified on the inner side by the preceding volution, pointed at 

 the upper end and broadly rounded at the base. Surface of the shell smooth and 

 substance very thin. 



The form of the shell is much like that . of a Macrocheilus, but the 

 substance is much thinner than those usually are, and the base of the 



