;22 



NEW YORK STATE MUSEUM 



It will however, be noted that not only the greatest number of 

 species' occur in Europe, but also that it does not appear m the 

 American continental basin proper until Cincinnati time though m 

 the Champlain basin it was already present during the Beekmantown 

 age and around the Adirondack region in Trenton time. It is not 

 cited from the Pretrenton Newfoundland embayment. 



Trochohtes is phylogenetically connected with the more primitive 

 genus Litoceras by the genus Trocholitoceras, which is -p"^ 

 by one species from the Fort Cassin beds ( T . w a c o 1 1 1 Hyatt) 

 and a doubtful congener from the Baltic basin. Litoceras is re- 

 stricted to the Newfoundland embayment. Present evidence wovild 

 hence indicate that this race originated in the -^^hwestern AtlanUc 

 sea, but spread with the appearance of the genus Trochohtes to both 

 the British embavment and the Baltic sea. . . ^, 



The genus Plectoceras finally existed in one species m Chazy time 

 in the Newfoundland embayment and Champlain basin, persisted m 

 Trenton time in the same region and in Niagaran time reached the 



Mississippian sea. , , , 



In regard to the Lituitidae, Hyatt [1894^ P- 504] makes the fol- 

 lowing interesting statement: 



All of these forms known to me occur in the Orthoceran and 



more southern faunas of the same stages . , P 



Foord doubts the appearance of true Lituites in the rocks of Great 

 Britain and I thnk he could have positively denied their appearance 

 fheJe since L ''ibex sp. Sowerby certainly has none of the usual 



characteristics of any of this family. ;tuitidae from 



Hyatt does not cite any representatives of the Lituitidae Irom 

 the Champlain basin, nor have we observed any in either the Beek- 

 mantown or Chazy beds of that region. He describes, however, m 

 C y c 1 o 1 i t u i t e s a m e r i c a n u s , from the Gargamelle cove 

 in Newfoundland, a lituitid from the Newfoundland basm, and in 

 Ancistroceras (?) dyeri from the Niagaran near Chi- 

 cago and Rhynch orthoceras (?) dubium from the same 

 group in Indiana, two later representatives of that family from the 

 Lerican basin. In Europe the family is absent, or nearly so, from 

 the Atlantic and Bohemian-Mediterranean basms, but remarkably 

 well represented in the Lower Siluric of the Baltic basin by the 

 genera Cyclolituites, Lituites, Angelinoceras, Holmiceras, Ancistro- 

 ceras and Rhynchorthoceras. . k . -frnm more 

 Hvatt's suggestion that the Lituitidae are absent from more 

 southern fauna's of the same stages " would seem to hint at climatic 



