526 NEW YORK STATE MUSEUM 



I 



lachian trough) in part of the Beekmantown stage stood in closer 

 marine connection with the Pacific basin than with the Atlantic. 



In the Chazy rocks proofs of a closer connection between the 

 Champlain basin and Newfoundland embayment become more fre- 

 quent among the Champlain cephalopods and the faunas of the 

 Champlain basin, the St Lawrence channel and the Mingan islands 

 have in common a number of forms other than cephalopods. Of the 

 24 species of Chazy cephalopods here described, 4 are known from 

 the Mingan islands. 



Freeh [1897, p. 93, 100] has inferred from an analysis of the 

 trilobite genera and species of North America and Europe, that 

 the Mississippian sea and Appalachian valley trough had no con- 

 nection with the Atlantic sea, the Bohemian-Mediterranean and 

 the Baltic basins during the earlier Lower Siluric era and that 

 an exchange of species did not begin until the Trenton period. The 

 inferences to be drawn from the distribution of the cephalopods here 

 described would seem to corroborate this view. 



On the other hand the Newfoundland embayment does not seem 

 to have stood in such open and direct connection with the Atlantic 

 sea, as Freeh's chart [op. cit. chart II] would indicate. We have 

 before pointed out that the common possession of the important 

 genera Eurystomites, Tarphyceras, Deltoceras and Plectoceras by 

 the Newfoundland and Canadian-Champlain basins and their absence 

 in the Atlantic basin in the early Lower Siluric could only be ac- 

 coimted for by the assumption of a connection of the Newfound- 

 land basin with the American basin closer than that with the Atlantic 

 basin at some time previous to the Fort Cassin stage. It must, how- 

 ever, be conceded here that in the great number of genera of ortho- 

 ceraconic and cyrtoceraconic forms, which have been excluded from 

 the discussion for reasons before stated, many may be contained 

 which are common to the Atlantic basins and Newfoundland 

 embayment. 



A like restriction as that here placed on the inference of a separa- 

 tion of the Newfoundland embayment and Atlantic basin would have 

 to check a conclusion of a closer connection between the Champlain- 

 Newfoundland sea and Baltic basin, which apparently follows easily 

 from the greater number of common genera, listed in the synoptic 

 table on page 513, the checking being necessary on account of the 

 fact that the important family of the Lituitidae, which is so char- 

 acteristic of the Baltic basin, failed entirely to reach the Champlain 

 basin and is known from the Newfoundland embayment in but one 

 species. It is different with the evidence in regard to a connection 



