REVIEH^S 543 



With our present knowledge there are thus 1 1 3 recognizable, distinct 

 specific forms in the fauna of the Oriskany at Becraft Mountain, and of these 

 <54 are identifiable with species already known or are clearly new forms 

 peculiar to the fauna. Of the 94, 25 preceded the introduction of the 

 Oriskany sedimentation, having been first described from the fauna of the 

 Helderbergian. In the arenaceous beds of the Oriskany 23 occur; 10 range 

 upward into the faunas of the Upper Helderberg (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 recorded by Schuchert. The fauna contains 35 species which so far as 

 known are peculiar to it. On farther analysis of the 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 

 gasteropods 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. 



The faunal values of the different species are then summed up. 



Concerning the nature of the Oriskany fauna of New York, the 

 author says : 



The fauna of the calcareous Oriskany is in no sense a mixed assemblage, 

 or an intermingling of faunas of adjacent provinces. The sequence of life 

 has continued without interruption from the Helderbergian (Kingston beds) 

 into the sediments of the Oriskany and Onondaga limestone. 



It is extremely probable that important variations from the fauna of the 

 Catskill shaly (New Scotland) limestone had already made their appearance 

 in the Becraft limestone, and that we first become acquainted with some of 

 these in the study of the calcareous Oriskany. No proof therefore could be 

 adduced more emphatically confirmatory of the intimate faunal relations of 

 the Helderbergian with the Oriskany fauna and its successors than the facts 

 brought forward in this paper. 



The fauna discussed is that of the calcareous facies of the Oriskany for- 

 mation. The sedimentary deposits of this and the neighboring sections were 

 essentially limestones notwithstanding the silicious content, whether diffused 

 through the mass or segregated as cherty secondary product. In the earlier 

 presentation of this fauna it was regarded as of lower Oriskany horizon on 

 account of the presence of many Helderbergian species, but we believe it will 

 be more correctly construed as the representative of the proper and normal 

 Oriskany fauna, the true fauna of this time-unit inclosed in the sediments of 

 its proper habitat. 



A chapter is devoted to discussing the Devonic age of the Helder- 

 bergian fauna and the base of the Devonic system in New York. 



