CRUSTACEA. 219 



TtJRRILEPAS TENER, 11. Sp. 



PL \ 11: xxxvi. i 



To this species are referred certain plates which have the same general out- 

 line ami surface features as in all the other specimens observed. One fragment 

 of shale retains ten of these plates over the surface of a square inch. The out- 

 line is equilaterally triangular and the surface nearly flat : the nucleus apical ; 

 the anterior and posterior margins straight, diverging at an angle of seventy-five 

 degrees: the basal margin is gently sinuous, curving upward toward the poste- 

 rior, and downward toward the anterior margin. Along the posterior margin, 

 the plate is abruptly deflected toward the opposite side, but this is only tor a 

 very short distance. When the plates are not flattened there appears to be an 

 elevated fold or broad ridge, situated in front of the axial line of the plate, 

 running from the apex to the basal margin. The concentric striai are tine, ele- 

 vated and crowded closely together, becoming obsolete just before reaching the 

 anterior margin. As in other forms of this genus, these lines curve upward at 

 or near the anterior and posterior margins. 



All the specimens observed have about the same Length and height, which 

 is 3.5 mm. 



Distribution. Hamilton group. In the lower shales at Centerfield, Ontario 

 county. 



TURRILEPAS(?) NEWBERRYI. 



PLATE XXXVI. FIGS. 16-19. 



Plwmidites Neibberryi, Whitfield. Annals New York Acad. Sciences, vol. ii, No. S, p. 217. 1 S82. 

 Plumviites Newberryi, Whitfield. Pal. Ohio. vol. iii. pi. viii, figs. <i-ll (unpublished). 



The specimens referred to this species consist of detached plates, of large 

 size, and generally obliquely sub-triangular outline. They are usually flattened 

 in the shales and somewhat indistinctly preserved, but were evidently of sub- 

 conical form. With a single exception, the nucleus is apical and inclined 

 slightly to one side, the anterior margin gently incurved, the posterior convex, 

 and the basal margin sinuous, a feature caused by a broad depression running 

 from the apex obliquely backward. A single specimen preserved in a rolled con- 



