348 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



east. At Albany and at Schenectady, in Ulster and Green Counties, 

 the dip is E.S.E., and very high. 



Thickness. — The maximum thickness in Schoharie County is 700 

 feet. It varies from 500 to 800 feet on the Hudson River in the 

 eastern part of New York (Mather). On the west of Lake Cham- 

 plain, the thickness is 500 feet ; but at Schenectady, the Frankfort 

 Slate alone is 500 feet thick (Mather). 



Fossils. — Consult the General Table No. I. and Table No. II. 



Frankfort Slate and Sandstone are very poor in fossils, except in 

 Graptolites, of which it possesses ten species. 



The animal remains are 103 in species, of which 42 have been de- 

 rived from previous strata, and most of them from the Trenton Group. 

 We here notice especially the effects of sediment on Invertebrate 

 life. Most of the Brachiopoda, Monomyaria, Crustacea, Gasteropoda, 

 and Cephalopoda have disappeared ; and there are few Zoophytes, 

 for want of lime. 



Several Trenton fossils (Strophodon semiovalis, Leptcena alternate/, 

 Orthis testatus, Calymene senarid) being continued through Utica 

 Slate into this group, we may almost consider it as a continuation of 

 Trenton Limestone, beginning with a shaly limestone passing through 

 shale and shaly sandstone to the end of the series. Many of the 

 Brachiopoda of Trenton Limestone are characteristic of the upper 

 part of this group (Hall). The Orthocerata are sometimes flattened. 

 The Zoophytes here are very few (5), for want of lime. 



Fossils typical. — These are numerous (60), because nearly every 

 order has a number of representatives, especially the Dimyaria. Cyrto- 

 lites ornatus (Porcellia) is peculiar to the upper part of the Hudson- 

 River- group. It was at one time supposed that no fossils were 

 transmitted into the newer groups ; but Table II. shows that 14 

 of this group pass upwards beyond the Oneida Conglomerate. They 

 are principally Brachiopoda. 



Fossils occurrent in Europe. — Graptolites Sagittarius; G. scalaris; G. 

 tenuis; Ptilodictya lanceolata ; Glyptaster brachiatus ; Leptaena alternata; 

 L. depressa; L. (Stroph.)grandis; Orthis lynx; O. biforata; O. occidentalis, 

 Lyell; O. parva; O. testudinaria ; Spirifer biforatus; S. lynx; Terebratula 

 bidentata; A try pa reticularis; Trinucleus Caractaci; Avicula demissa?; 

 Clidophorus planulatus ; Lyrodesma plena ; Modiolopsis modiolaris ; 

 Nucula levata; N. poststriata; Orthonota nasuta; Cyrtolites ornatus; 

 Lituites planorbiformis ; Bellerophon bilobatus. 



Fossils recurrent in New York. — The received organisms of the 

 Hudson-River-group are principally Brachiopoda (14). The others 

 are scattered, a few of each order. The fossils which this group 

 transmits are Leptcena depressa, L. sericea, Atrypa didyma ?, Theca 

 triangularis, Calymene Blumenbachii. 



Grey Sandstone, 



Mineral Character. — In some parts of this basin a grey sandstone 

 succeeds the Hudson-River-group. It is of a uniform character, 

 and may be described in general as an even-bedded greenish-grey 

 stratum, fine-textured, siliceous, but not vitreous, with a little mica 



