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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 in the 

 American continental basin proper until Cincinnati time, though in 

 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. 



Trocholites is phylogenetically connected with the more primitive 

 genus Litoceras by the genus Trocholitoceras, which is represented 

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

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

 stricted to the Newfoundland embayment. Present evidence would 

 hence indicate that this race originated in the northwestern Atlantic 

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

 the British embayment and the Baltic sea. 



The genus Plectoceras finally existed in one species in Chazy time 

 in the Newfoundland embayment and Champlain basin, persisted in 

 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 

 Vaginatus limestones of northern Europe and Niagara limestones 

 and Quebec faunas in this country. They seem to be absent from 

 more southern faunas of the same stages. 



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

 Britain, and I think he could have positively denied their appearance 

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

 characteristics of any of this family. 



Hyatt does not cite any representatives of the Lituitidae from 

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

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

 C y c 1 o 1 i t u i t e s americanus, from the Gargamelle cove 

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

 Ancistroceras (?) dyeri from the Niagaran near Chi- 

 cago and R h y n c h orthoceras (?) d u b i u m from the same 

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

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

 the Atlantic and Bohemian-Mediterranean basins, but remarkably 

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

 genera Cyclolituites, Lituites, Angelinoceras, Holmiceras, Ancistro- 

 ceras and Rhynchorthoceras. 



Hyatt's suggestion that the Lituitidae are ■ " absent from more 

 southern faunas of the same stages " would seem to hint at climatic 



