30 Bulletin 14 296 



localities, but is almost always partially exfoliated or in casts. 

 More perfecfth' preserved specimens are needed to make sure its 

 specific identification. 



As would be expedled from the nature of the sediments, pel- 

 ecypods are almost entirely wanting. 



The Birdseye limestone in this sedlion is a lighter colored, 

 purer subdivision of the Black River, grading gradually into it. 

 The latter can here be subdivided into faunal zones, which 

 might be named from the class of fossils which is most abundant 

 in them. At the base is the Birdseye zone, 5 feet in thickness, 

 characterized by Phytopsis tubulosits Hall and Leperditia fahdites 

 Conrad. Above it, the Pelecypod zone, 7 feet in thickness, con- 

 tains an abundance of lamellibranchs of the genera Ctenodonta, 

 Cuneaniya and Whitella. The remainder can be put into one 

 zone, 55 feet in thickriess, in which both the brachiopoda and 

 Crustacea are common, the latter being more prominent in the 

 lower 30 feet and the brachiopoda in the upper part. 



There seems to be a direCl: connedlion between the lithologi- 

 cai chara(5lers of these zones and the fossil contents. The first is 

 a very pure, light colored, fine grained limestone; the second, 

 pure, lumpy, black and heavy bedded; the third, impure, coarse, 

 light gray and rather crystalline in the lower part, becoming finer 

 grained, but still impure, toward the top. 



The fossils which at this locality occur commonly in the 

 Black River, and in none of the other formations, are: Maclurea 

 logani Salter, PleHorthis plicatella Hall, Strophomena incurvata 

 Shepard, Zygospira recurvirostris Hall, Stroniatocerium rogosum 

 Hall, Columnaria alve.olata Goldfuss, and Leperditia fabulites 

 Conrad. The abundance of Rhy7lchotrema incsquiva/ve Castelnau, 

 Ceraiirus pleurexanthemus Green, and Dalmanites callicephalus 

 Hall is a feature of these limestones at many localities and is well 

 illustrated in this sedlion. Only the branching form oi Moiiticuli- 

 pora lycoperdon Say occurs below the Trenton, thus agreeing with 

 the statement of E. R. Cummings* regarding the same fossil in 



*Lower Silurian Sedlions. Bull. N. Y. State Museum, No. 34. Al- 

 bany, 1900. 



