CONTRIBUTIONS TO PALiEONTOLOGY. 43 



times mucli coarser than the revolving striae ; and finer striae are implanted 

 between the coarser, and do not reach the suture-line. In old specimens, 

 the revolving band is a quarter of an inch in length. The species has had a 

 wide geographical distribution, and its vertical range is not less than one 

 thousand feet. A very symmetrical specimen has a diameter of a little more 

 than two inches, and is nearly an inch and three-fourths in height. Another 

 specimen, which has suffered some compression, has a breadth of about three 

 inches, with nearly the same height of spire. 



Geological formal ion and locality. In the Corniferous limestone : llel- 

 derberg mountains, Williamsville, Clarence-hollow, N.Y.; and Falls of the 

 Ohio river. In the Hamilton group : York, Moscow, Genesee, Skeneateles 

 lake, etc., N.Y. 



PLEUROTOMARTA DORIS (n.s.) n. ^/ f 

 Shell very depressed-conical, the elevation of the spire being about 

 two-thirds the width across the base of the shell. Volutions three 

 or four, very gradually expanding, their elevation above the su- 

 ture line being greater than the width exposed : body- volution 

 moderately ventricose and rounded above; the periphery a little 

 contracted vertically, and the lower side rounded and expanded 

 more abruptly towards the aperture, gently depressed towards the 

 centre, which is partially umbilicate. Aperture nearly circular. 

 Surface marked by strong revolving striae, which are crossed by 

 fine and less conspicuous concentric striae, giving sometimes a 

 denticulate character at .the crossing of the two series. Shell of 

 moderate thickness. Suture neatly defined, not canaliculate. 



This species is less rotund than the P. lucina; the spire is more elevated, 

 and the revolving striae proportionally stronger. 



Geological formation and locality. In the Schoharie grit, Schoharie ; 

 and in the Corniferous limestone, Clarence-hollow, Erie county, N.Y. 



PLEUROTOMARIA UNISULCATA (Conrad). 



Pleurotomaria unisulcata : Conrad, Jour. Acad. Nat. Sciences, Philadelphia, 1842, 



pjig. 271, pl.iri. f. 9. 



" Short - fusiform : spire conical - depressed ; upper surface of the 

 " large volution slightly concave from the outer margin to a ca- 

 " rinated line which borders a transversely rugose sulcus; an- 

 " other, but more obtuse line, margins the suture; penultimate 

 " whirl rounded, obtusely carinated at the suture; base nearly 



1861.1 



