DESCRIPTION OP SPECIES 257 



upper half of the body whorl which show excellently on the light color 

 substance of the shell; indications of color markings on the lower half 

 of the whorl which, however, is much discolored by the dark, carbon- 

 aceous shale in which the shell was embedded. Shell thick. 



Dimensions. Height 9.5 mm. (slightly crushed); width 14 mm.; 

 height of body whorl 8.5 mm. 



Remarks. In spite of its imperfect condition, this interesting 

 little shell differs so markedly from any described species, and shows 

 so excellently the color markings which are sometimes retained on 

 representatives of the genus Naticopsis, that it seems justifiable to use 

 it as the type of a new species. The single specimen which has been 

 found is slightly crushed with a portion of the lower half and the end 

 'of the last volution missing. The species is characterized by its low 

 spire and explanate shape (with allowances made for compression). 

 It is closely related to Platyceras ? peoriense, N. nanus, and N. splendens, 

 but differs from all of these forms, especially from the two latter ones, 

 in the above-mentioned ways. The shell is thick, while that of P. ? 

 peoriense which it resembles closely is said to be thin. 



Horizon and locality. Lower Mercer black shale: Stark County, 

 near East Greenville, Locality 52, r. 



Naticopsis tortum (Meek) 

 PL XV, figs. 17, 18 



1871 Platyceras tortum. Meek, Proc. Acad. Nat. Sci. Phil., p. 171. 



Coal Measures: Greentown, Summit County, Ohio. 

 1875 Platyceras tortum. Meek, Pal. Ohio, Vol. II, p. 345, PL 20, Figs. la-c. 



Coal Measures: Greentown, Stark County, Ohio. 



Meek's description. "Shell very thin, dextral, attaining about 

 a medium size, in young specimens composed of about one and a half 

 to two volutions, subglobose, these first turns being contiguous, rounded, 

 and rapidly increasing in size, after which the next turn, which com- 

 poses the larger part of the shell, becomes free, very oblique, and in- 

 creases more gradually in size, thus making the entire outline very 

 obliquely elongate-rhombic; body volution a little flattened on the 

 upper slope, subangular above, and somewhat prominently rounded 

 near or below the middle; aperture apparently oval-suborbicular; lip 

 without sinuses. Surface non-plicate, and with only moderately dis- 

 tinct lines of growth." 



Dimensions. The dimensions of the figured specimen are: length 

 32 mm., width 24 mm., length and width of aperture about 21 mm. 



Remarks. This species is represented in the collections of Potts- 

 ville fossils studied by about six specimens from the McArthur lime- 

 stone which have been for the most part distorted vertically by press, 

 o G. B. 25. 



