86 
PALAEONTOLOGY OF NEW YORK. 
Pleurotomaria quadrilix, n. sp. 
PLATE XXX, FI(x. 18. 
Shell trocliiform, depressed-conical, a little higher than wide. Volutions five 
or six, moderately convex on the upper side, the higher ones minute, or 
gradually increasing in size from the apex and becoming somewhat ventri- 
cose. Aperture unknown. 
Surface marked by simple sharp ecpial concentric stride, which make a slight 
curve just below the suture, and are thence directed backward to the 
upper margin of the peripheral band. The striae are about equal to half 
the space between them; below the peripheral band on the outer volution 
they are nearly vertical for a short distance. The band is compound, 
being limited above and below by a canaliculate belt, which includes a 
somewhat wider depression between. There are no visible revolving 
striae. 
This species differs conspicuously from any of those described in this volume 
by the character of the peripheral band, which presents the appearance of 
being limited above and below by a sharply grooved carina leaving a narrow 
intermediate space. The absence of revolving carinae, other than those of the 
periphery, is also a distinguishing feature. In the strength of the concentric 
striae it is intermediate in character between the P. nitella and P. adjutor. In the 
character of surface striae and the peripheral band it is similar to P. costulato- 
canaliculata of Sandberger; the volutions are about equally convex, but the 
spire is more elevated, and the band appears entirely above the suture-line in 
the higher volutions. In all its essential features, except in the greater eleva¬ 
tion of the spire, this species corresponds to the P. lenticularis of Goldfuss, from 
the Devonian rocks of Nassau. 
This fossil is extremely rare in the rocks of New York, since, at the 
present time, we know but a single example. 
Formation and locality. In the Upper Helderberg limestone at Babcock’s 
Hill, town of Bridgewater, Oneida county, N. Y. 
