24 m:\v vokk state mtskim 



Aiiuni«r tho Kussian forms is tij^ured a pediclo valve with 

 dopress(Hl umbo and vim\v convex pallial region, ovhicli is quite 

 similar to our form. Takinj? all these facts into account, it 

 appears that the internal cliaracters will hardly furnish any 

 points of difference between llie forms, and that, when the gen- 

 eral form and the exterior are compared, the Trenton form com- 

 bines the cardinal extremities of the British with the striated 

 surface of the Russian epecies. 



TRIPLEGIA Hall 

 Triplecia nucleus Hall 

 A t V y pa nucleus Hall. Tal. N. Y. 1847. 1 :138 

 A small Triplecia, evidently identical with Triplecia 

 nucleus Hall, was found to be common in the gray crystal- 

 line liniiestone iK^bbles of the conglomerate; a few specimens 

 wei-e also obtainetl from the com]xict reddish limestone with 

 ostracodes. Triplecia nucleus has thus far been found 

 only in the middle Trenton of New York. (Group-s G, 7) 



ORTHis Dalman 

 Orthis tricenaria Conrad. Acad. mat. sci. Phil. Proc. 1843. 1:333 



Orthis tricenaria occurs quite frequently in typical 

 specimens of somewhat smaller size than those from the western 

 side of the Adirondacks, in the gray crystalline and compact 

 black limestone pebbles and in the cement. Its similarity to the 

 Chazy form, Orthis c o s t a 1 i s , together with the occurrence 

 of numemus cranidia and pygidia of Ami»yx and Remopleurides 

 in the compact black limestone was at the first collecting quite 

 suggestive of the Chazy age of the compact black limestone i)eb- 

 bles; a suggestion, however, which the common occurrence of 

 typical Trenton fossils in the same pebbles proved to be mislead- 

 ing. (Cement and groups H, G) 



Orthis tricenaria is reported by Hall from the lower 

 Trenton of Middleville; in tlie west it ranges from the Stones 

 river (Lowville) beds through the Black river beds into the Tren- 

 ton. Dr Wliite did not locate it in (lie Tn^nton and Kathbone 

 brook sections. 



