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 IS 1(1. described an entire individual from the limestone at Auburn, Cayuga 

 county, under the name of Odontocephalus selenurus (Inc. at.). 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 bad 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 ami disappear opposite the lateral extremities of the anterior 

 lobe of the glabella. In like manner, in the sub-genus Corycephalus, the 

 Lower Helderberg species I), dentatus seems to be the forerunner of D. regalis 

 of the Schoharie grit, and D. pygmmis of the Corniferous limestone, in all of 

 which the dentate ornamentation extends around the entire cephalic margin. 



Distribution. Upper Helderberg group. Corniferous limestone: Marbletown, 

 Qlster 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 LeRoy, Genesee 

 county ; Clarence, Erie county. 



