TRENTON CONGLOMERATE OF RYSEDORPH HILL 17 



Eafinesquina deltoidea Conrad var. An. geol. rep't. 1838. p. 115 

 In the gray, cryistalline limestone occurs a Rafinesquina, which, 

 on account of certain peculiarities, is worthy of notice. While 

 it has the outline of Rafinesquina deltoidea, it is 

 more convex, holding in this feature an intermediate position 

 between R. deltoidea and R. c a m e r a t a , as figured by 

 Hall, and it lacks the concentric wrinkles on the depressed con- 

 vex cenitral disk, usually occurring in both of these species. Its 

 most striking feature, how^ever, is the entire absence of the fine 

 radiating striae between the coarse ones, having only about 15 

 prominent, equidistant striae on an otherwise smooth shell. In 

 view, however, of the great variations ofR. alternata and 

 its allies, R. earner at a and R. deltoidea, on account 

 of which it is often difficult to even assign a normal form 

 to any of these three species, it would seem unwarranted to give 

 any importance to such a varietal difference, if it were not fo^r 

 the fact, that the whole fauna of the conglomerate differs in so 

 many of its constituents from the other New Y'ork faunas, 

 thereby giving alsO' to such varietal differences a certain 

 significance in the comparison of provincial faunas. 



According to Hall the species abounds in the Trenton lime- 

 stone at Trenton Falls and at Sugar river in Lewis county and is 

 scarcely known to occur in the Champlain valley. Dr T. G. 

 White found that it characterizes certain Middle Trenton beds at 

 Trenton Falls, and that it also occurs in the Trenton of the 

 Champlain valley. Winchell and Schuchert report it from the 

 middle and upper Trenton and the Lorraine beds of localities 

 in Minnesota and Wisconsin ; and according to Davidson ^ it is 

 widely distributed in the Caradoc of Great Britain and through 

 corresponding beds o<f Norw^ay and Russia. The latter state- 

 ments, however, are questioned by Winchell and Schuchert, as 

 the identity of the European and American forms is still 

 doubtful. (Group 7) 



I Monograph Brit. Sll. Brach. 18T1. v. 3, pt 7, p. 292. 



