52 
PALEONTOLOGY OF NEW YORK. 
Observations. This species was originally described by Professor Amos Eaton, 
from a caudal shield bearing elongate, divergent spines, giving the posterior 
margin a crescentiform outline; and at the time of publication this was the 
only part of the animal known. The original of Culymene? odontocephala. Green, 
was a detached head, and was regarded as a distinct species until Mr. Conrad, 
in 1840, described an entire individual from the limestone at Auburn, Cayuga 
county, under the name of Odontocephalus selenurus {loc. cii.). The species is 
abundant in many outcrops of the Corniferous limestone, and appears to be 
restricted to this formation. Entire individuals are, however, seldom met 
with unless in an enrolled condition. Although very closely allied in general 
features and in many details, with the associated species here referred to the 
same sub-generic group, Dalmanites selenurus is distinguished by the follow¬ 
ing persistent features; (a) the denticulations on the frontal margin number 
nine; (b) the extremities of the cheeks are obtuse or produced into minute 
spines; (c) the caudal spines are long, slender, divergent and bent upward, 
with their bases distant; (d) the number of pleural annulations on the pygidium 
is eight, with indications of a ninth. The peculiar frontal ornamentation in 
the species of Odontocephalus appears to have had its inception in the marginal 
crenulations or thickenings on the frontal limb of Dalmanites pleuroptyx of the 
Lower Helderberg, a feature reproduced in the species D. anchiops of the Scho¬ 
harie grit. In both these species the crenulations are longest and most con¬ 
spicuous in front and disappear opposite the lateral extremities of the anterior 
lobe of the glabella. In like manner, in the sub-genus Corycephalus, the 
Lower Helderberg species D. dentatus seems to be the forerunner of D. regalis 
of the Schoharie grit, and D. pygmceus of the Corniferous limestone, in all of 
which the dentate ornamentation extends around the entire cephalic margin. 
Distribution. Upper Helderberg group. Corniferous limestone; Marbletown, 
Ulster county; near Clarksville, Albany county; Schoharie, Schoharie county; 
Eastman’s and other quarries, Waterville, Oneida county; Cherry Valley, Otsego 
county; Manlius, Onondaga county; Auburn, Cayuga county; Canandaigua, 
Clifton Springs and Phelps, Ontario county; Lime Rock, near Lelloy, Genesee 
county ; Clarence, Erie county. 
