864 THE PALEONTOLOGY OF MINNESOTA. 



[Cyrtolltes parvus. 



CYRTOLITES PABVUS, n. sp. (Ulrich.) 



PLATE LXII, FIGS. 45 47. 



Shell small, about 7 mm. in diameter, 6 mm. wide at the aperture, consisting 

 of about two rapidly enlarging volutions, subquadrangular in section and somewhat 

 wider than high; dorsum carinated, the keel not very prominent, minutely wavy in a 

 side view; sides narrowly rounded, scarcely angular; dorsal slopes gently convex, with- 

 out undulations except near the aperture where several obscure ones may be noticed. 

 Surface with comparatively coarse lines of growth, curving strongly backward from 

 the edge of the umbilicus to the dorsal carina which they cross without interruption. 

 These lines are connected by more closely arranged and very delicate obliquely 

 revolving lines, which, being lower than the transverse set, might easily be 

 overlooked. On the last turn seven or eight of the transverse lines occur in 2 mm. 



Considering the size of the shell, the surface markings are stronger than in any 

 of the other species of the genus. From C'. carinatus Miller, which it resembles 

 most, it differs also in having the sides of the volutions narrowly rounded 

 instead of sharply angular. In C. retrorsus and C. ornatus the surface ornamen- 

 tation is much more distinctly reticulated, and, while the former has a much 

 stronger keel and concave dorsal slopes, the latter is especially distinguished 

 by the absence of a sinus in the outer lip and consequently in the more strictly 

 transverse course of the surface markings. Internal casts of Cyrtolitina nitida 

 resemble testiferous examples of this species; but if this fact is borne in mind, and 

 further that in the former the back is flattened, the volutions more compressed 

 laterally, and the surface markings of the cast thicker and wave-like rather than 

 thread-like, it is almost impossible that confusion between them can ever occur. 



Formation and locality.- Near top of Trenton group at Covington, Kentucky. 

 Collection. E. O. Dlrich. 



CYRTOLITES DISJUNCTTJS, n. sp. 



PLATK LXII, PIGS. 48 and 49. 



Shell about 24 mm. in hight, consisting of about two entirely free or disjoined 

 whorls, coiled very nearly or quite symmetrically; volutions strongly and sharply 

 carinated dorsally, the sides somewhat narrowly rounded within the center, and 

 strongly undulated transversely; ventral side less convex, with two abruptly 

 elevated narrow central carina}, forming a groove with raised edges or what is 

 commonly called a "saddle"; hight of volutions increasing with age more rapidly 

 than the width, the transverse section, excluding the dorsal and ventral carinse, 

 changing from transversely subelliptical to almost circular at the aperture of a fully 



