30 PALEONTOLOGY OF NEW-YORK. 



50. 3. RAPHISTOMA PLANISTRIA (w. sj9.). 



Pl. VI. Figs. 3 a, b. 



Turbinate ; length and breadth nearly equal ; spire depressed ; apex a little elevated ; 

 volutions about four, angular ; outer one quite flat or a little concave above, scarcely 

 ventricose below ; surface marked by flat broad apparently imbricating striae, which are 

 bent backwards, and interrupted along a line near the middle of the upper part of the 

 whorls ; aperture narrow, trigonal ; umbilicus small. 



This shell differs from the last, in the greater proportional height, the narrow trigonal 

 aperture and small umbilicus, as well as in the flat plain striae. 



In general appearance, this species differs little from a small Trochus in the Trenton 

 limestone, and, on hasty examination, might be mistaken" by unpractised observers. The 

 spire in this shell, however, is more nearly flat, and the shell more extended below ; the 

 aperture also is longitudinal, while in that shell it is transverse. 



Fig. 3 a. View of the spire ; the striae flat and broad. The figure does not show the interruption. 

 Fig. 3 b. View from beneath, showing the umbilicus. The height of the shell is not shown here.* 



Position and locality. In the fine-grained subcrystalline and oolitic limestone, at Chazy 



village, Clinton county. (.state Collection.^ 



.51. 4. RAPHISTOMA PLANISTRIA, var. PARVA. 

 Pl VI. Figs. 3 c, d, e. 



Depressed-turbinate ; spire elevated in the centre ; volutions about five, outer one sharply 

 angular ; surface marked by fine scarcely distinct striae, which bend beickwards above and 

 forwards below the angle of the volution ; aperture longitudinal, narrow, trigonal. 



Length and height about equal. 



I have seen but two perfect specimens of this minute shell, though it is quite abundant 

 at Chazy, upon the worn surfaces of strata, often presenting vertical and horizontal sections. 

 From the great numbers of specimens of this size, and from the perfection of one or two 

 separate specimens, I am, for the present, inclined to separate it from the last, which it 

 resembles in form, but wants the distinct imbricating striae. 



Fig. 3 c. View of the spire. Fig. 3 d. Lateral view. Fig. 3 e. View of the aperture. 



Position and locality. In the grey fine-grained subcrystalline limestone, at Chazy village, 



Clinton county. State Collection. 



* Fig. 1 of this illustration shows the top of the spire, with the interrupted striae 

 along the middle of the upper side of the volution, which is omitted in the pjate. 

 Fig. 2 shows the height of the shell. 



