BEEKMANTOWN AND CHAZY FORMATIONS OF CHAM PLAIN BASIX 521 



The genus Tarphyceras has a distribution, which in Pretrenton 

 time is identical with that of Eurystomites. It is represented by 

 three species in the Newfoundland embayment, by four in the Cham- 

 plain basin (one from Philipsburg), and by one in the Appalachian 

 trough in Virginia. It has hence the center of its development 

 approximately in the Champlain basin and extends into the New- 

 foundland embayment, and the middle Appalachian trough. A later 

 form (Discoceras convolvens ? Angelin and Lindstrom) 

 from the Baltic basin is referred by Hyatt with doubt to this genus. 



The genus Deltoceras is known by one species from the Beekman- 

 town formation of Newfoundland and one from the lower Chazy of 

 the Champlain basin. 



The genus Barrandeoceras is present with two species in the 

 Chazy formation of the Mingan islands (Newfoundland embay- 

 ment), one of which extends into the Champlain basin ; with three in 

 the Bohemian basin and it persisted in L i t u i t e s convolvans 

 Hall into the Black river formation of the Alississippian basin. Its 

 distribution points to a previous marine connection between the 

 Bohemian-Mediterranean sea and the Newfoundland embayment by 

 way of the Atlantic. 



A genus of the Tarphyceratidae which, though not observed in 

 the Champlain basin of New York and Vermont, invites mention, is 

 Aphetoceras. This is known in two species from the Beekmantown 

 of Philipsburg and in two more from the same formation in New- 

 foundland. 



The genus Schroederoceras is distinctly Baltic in its distribution, 

 for it is there represented in the Lower Siluric with no less than 

 eight species against but two in the Champlain basin. 



The genus Trocholites is again quite suggestive in its distribution. 

 Even in its restricted scope it has a very wide range and geographic 

 distribution, when compared with the other nautiloid groups here 

 described. Besides the two forms, originally referred by Conrad to 

 this genus ( T . am m o n i u s and planorbiformis) , 

 Schroder recognizes 10 species in the Lower Siluric of the Baltic 

 basin (mostly from the Echinosphaeriten-Kalk) , and Hyatt refers 

 to this genus — besides the Fort Cassin form described in this paper 

 — a Canadian species from the Falls of Montmorency, another from 

 the Cincinnati group (besides one previously made known 

 by Miller and Dyer) and two more, published by Blake from the 

 Lower Siluric of England. Trocholites ranges therefore through 

 the whole Lower Siluric and is found in both Europe and America. 



