516 
PALAEONTOLOGY OF NEW-YORK. 
Graptolitluis wliitfieldi (n. s ). 
Stipe simple, flat, gradually expanding from the base to near the middle 
of its length, the upper part gradually narrowing in the direction of the 
apex, rarely continuing of the same width above the middle : serra- 
tures shallow, angular; the upper margin of the denticles short and 
nearly rectangular to the axis, the lower side twice as long as the 
upper, the tips furnished with mucronate or short setiform extensions 
which project in a line with the upper margin of the denticle. Serra- 
tures twenty-two to twenty-eight in the space of an inch. 
Length from one inch to an inch and a half. 
This species has the general form and proportions of the G. pristis ( Hall, Pal. 
New-York, Yol. i, pa. 265, pi. 72, f. 1); but that species does not contract its width 
towards the upper extremity, the denticles are concave above, and the points di¬ 
rected upwards. The form of the serratures and denticles is quite diiferent in the 
two species, and the setiform processes are never observed on that species as in this 
one, where it is a constant feature. 
The present form is not unlike the one described as G. mu- 
cronatus ( Hall, Pal. New-York, Yol. i, pa. 268, pi. 73, f. 1) ; 
but that species has differently formed serratures and denticles, 
and the entire stipe is more lax. The upper margins of the den¬ 
ticles are traceable nearly to the midrib in well-marked speci¬ 
mens of that species, and the mucronate tips appear to be formed 
by the gradual narrowing and extension of the substance of the 
denticle; while in this one, it is an abrupt extension from the 
apex of the denticle. 
For the purpose of comparison with the G. pristis , I have 
presented figures of the two species, which are enlarged to twice 
the natural size. 
These specimens are from the same locality, and the differences 
are constant. 
Fig. 1. G. wliitfieldi. Fig. 2. G. pristis. 
Geological position and locality. In the shales of the Hudson-river group : Near 
Albany. 
