68 NEW YORK STATE MUSEUM 



introduction of Oriskany sedimentation, having been first described from 

 the fauna of the Helderbergian. In the arenaceous beds of the Oris- 

 kany 23 occur; 10 range upward into the faunas of the Upper Hel- 

 derberg (Ulsterian), but a part of these are restricted to the sandy, 

 lower beds of this formation (Schoharie grit), and others have been 

 noted only in the chert beds of Ontario, Canada, where the intermixture 

 of Oriskany and Onondaga species is well marked and has been re- 

 corded by Schuchert. The fauna contains 35 species which so far as 

 known are peculiar to it. On farther analysis of the foregoing table, 

 it is evident in some cases that species which range down and upward 

 are restricted to particular groups. Thus the alien trilobites are from 

 the Helderbergian ; the gastropods are exclusively Oriskany ; while the 

 alien lamellibranchs are mostly Helderbergian. But the leading factor 

 of the fauna, the brachiopod, has its derivation as freely from below 

 as in the Oriskany invasion. 



FAUNAL VALUES OF THE SPECIES 



The following is a statement of the faunal values of these species 

 or their closest affiliations with species of other faunas. 



Dalmanites (Synphorla) stemmatus C. — D. (Syn.) Maecurna C, Maecuru sandstone, 



Amazonas 

 " var. convergens C. 



D. pliacoptyx H. & O. — idem, Onondaga limestone, Ontario 

 D. bii^ignatus C. — D. dentatus Barrett, Helderbergian, Port Jervis 



D. pleuroptjx Conrad, Helderbergian and Ulsterian, N, Y. 

 Phacops correlator C. — Ph. anceps C, Onondaga limestone, Ontario 



Ph. braziliensis (7., Maecuru sandstone, Amazonas 

 Ph. logani H. — idem, Helderbergian, N. Y. 



Cordania becraftensis G. — Cord, cjclurus H. «fe C, Helderbergian, N. Y. 

 Cord, hudsonica C. 



Cj'phaspis minuscula H. — idem, Ulsterian, N. Y. 

 Proetus conradi II. — idem, Schoharie grit, N. Y. 

 Acidaspis tubereulata Conrad — idem, Helderbergian, N. Y. 

 Lichas cf. pustulosus H. — idem, Helderbergian, N. Y. 

 Homalonotus sp. 

 Autodetus beecheri C. 



