62 NEW YORK STATE MUSEUM 



Hall, Hipparionyx proximus Vanuxem, Rensse- 

 laeria ovoides (Eaton) and the gastropod Platyostoma 

 ventricosa Conrad. 



As an example of a derived fossil we may cite Stromatopora, and 

 it is not unlikely that the cosmopolitan Leptaena rhomboi- 

 d a 1 i s owes its presence here to the same causes. The absence of 

 the Helderbergian strata at certain localities in the quadrangle 

 renders it highly probable that these two fossils were derived from 

 beds of this age which were planed away by the advancing Oris- 

 kanian sea. 



THE FAUNA OF THE ONONDAGA LIMESTONE 



Lying above the thin sands of the Oriskany comes the massive 

 Onondaga limestone. In the numerical abundance of its individuals 

 and in its diversified nature, as well as in the beauty of many of its 

 species, the Onondaga is the most noteworthy fauna to be found in 

 the local Paleozoic series. At certain places and at certain hori- 

 zons the rock may, it is true, be quite barren of fossils: sometimes 

 secondary crystallization has obliterated or at least obscured the 

 traces of life ; but, on the whole, it is a highly fossiliferous formation. 



At the famous collecting ground in the Split Rock quarries, the 

 sea must have literally teemed with life. Crinoidal fragments and 

 corals (many probably in the position of growth) are the most 

 abundant fossils, but bryozoa, brachiopods, gastropods and trilobites 

 are well represented. 



This assemblage gives a picture of the rich life of a favorable 

 Paleozoic marine environment, and, if one is permitted to judge it in 

 the light of what is going on today, he is justified in assuming a 

 warm sea of moderate depth, vigorous currents, and an abundant 

 food supply of minute organisms. 



In addition to the corals of difficult specific determination, but re- 

 ferable to the genera Zaphrentis, Heliophyllum and Favosites, it is 

 practicable to list here only a few of the most common fossils of the 

 local exposures, as : 



Atrypa reticularis Linn. 



Meristella nasuta (Conrad) 



Dalmanella lentiformis (Hall) 



Leptaena rhomboidalis Wilckens 



Platyostoma turbinata Hall 



Strophostylus varians Hall 



Platyceras (numerous species) 



Phacops cristata Hall 



Dalmanites (Odontocephalus) selenurus (Eaton) 



