86 
PALEONTOLOGY OF NEW YORK. 
Above both these pairs of spines are the bases of two or three strong tubercles, 
which were probably spiniform. The principal pair of spines was evidently. 
more divergent than the single pair in Lichas gryps. The lateral lobes are 
almost obsolete, each bearing a spine just within the orbital node. The pos¬ 
terior j)ortion of the head-shield has not been observed. 
Distribution. Upper Helderberg group. Corniferous limestone ; Schoharie, 
Schoharie county; LeRoy, Genesee county. 
[s.-G.] DICRANOGMUS, Corda. 1847. 
Lichas (Dicranogmus) ptyonurus, n. sp. 
PLATE XIX B, FIGS. 19-21. 
Cephalon sub-semicircular in outline. Surface depressed-convex, flattened above 
and sloping gently in all directions to the margin; indistinctly trilobate. 
Border narrow, slightly thickened and produced into short spines at the 
genal angles. 
Glabella large, sub-quadrate. Frontal lobe depressed, narrow, sub-rectan¬ 
gular ; its width less than one-third that of the glabella; not differentiated 
from the lateral lobes on the anterior third of the shield; extending to the 
occipital furrow and constricted just behind the middle by a transverse 
depression, which is continuous with the second pair of lateral furrows. 
First lateral furrows longitudinal, parallel, shallow and becoming obsolete 
on the anterior one-third of the shield; second lateral furrows strong, 
transverse, at right angles with the first pair, and extending to the palpebral 
furrow with a slight forward curve; third lateral furrows beginning at the 
termination of the second pair, thence backward, parallel for a short distance 
and merging into the occipital furrow. First lateral lobes large, indistinctly 
defined on the antero-lateral margins, and coalesced with the frontal lobe 
anteriorly, forming a single conspicuous, semicircular subdivision, extending 
for more than one-half the length of the head; second lateral lobes smaller, 
sub-quadrate, and distinctly separated from the palpebral lobes by a sulcus; 
third lateral lobes obsolete. Occipital furrow narrow, deeply impressed 
