LOWER SILURIAN SYSTEM OF EASTERN MONTGOMERY CO. 425 



above designation. Three miles north of Amsterdam it is said to 

 be " quite pure, compact and durable."^ 



In the Second annual report by Vanuxem the Trenton is definitely 

 spoken of as '* Trenton limestone " with the statement that " South 

 of the Mohawk the Trenton limestone both in Herkimer and Mont- 

 gomery counties rarely exceeds a thickness of lo feet nor much 

 beyond that thickness in any part of the latter county/'^ The 

 faunal character of the rock is stated as follows: 



This limestone is readily distinguished from all the other rocks 

 by the numerous individuals of the Leptaena alternata [R a f i n e s - 

 quina alternata (Con.) Hall and Clarke], Delthyris striatula 

 [Orthis (Dalmanella) testudinaria Dal. ?] , Orthoceras 



striatum, Bellerophon apertus^ Favosites , Calymene blumen- 



bachii [C. caUicephala Green], Cryptolithus tessellatus 

 [Trinucleus concentricus Eaton] , Isotelus gigas [A s- 

 aphus platycephalus Stokes] and cyclops [same as pre- 

 ceding] (p. 283). 



In the Fourth annual report Vanuxem says that on the Mohawk 

 river the Trenton is in no place 30 feet in thickness,^ but again 

 "On the Mohawk its thickness rarely exceeds 30 feet " (p. 371). 

 In his final report this statement is repeated with the addition that 

 " it is not so thick at the east as at the west end."^ Here also he 

 says that '' the gray variety of limestone does not appear upon the 

 Mohawk." 



In Mather's reports the occurrence of the Trenton in Schenec- 

 tady county near Amsterdam is several times mentioned specially 

 in the final report,^ and in this report a section is given made by 

 Cadet T. Seymour at " Marlit & Denham's quarries, near Hoff- 

 man ferry " which foots up 20 feet, 10 inches (p. 400). This may 

 be the Weatherwax quarries of the present paper. 



In the i^th annual report (1893) the Trenton is said to comprise 

 three principal members, a '* thick bedded, coarse grained, light 

 colored crinoidal limestone. . ~. underlaid by a series of thin 

 bedded, dark limestones, with more or less intercalated black 

 shale. . . Then there is a very massive, dark, coarse limestone 

 which begins as a basal series near the Mohawk in the eastern 



^Loc. cit. Assembly doc. no. 161, p. IfiS, 164. 

 ^Loc. cit. Assembly doc. no. 200, p. 275. 

 ^Loc. cit. Assembly doc. no. 50, p. 365. 

 *Geology of New York, pt 3, p. 49. 

 ^Geology of New York, pt 1, p. 397, 398. 



