520 NEW YORK STATE MUSEUM 



The genus Eiirystomites may be said to be typically American, 

 since of the eight species referred to it, one comes from Newfound- 

 land, five from the Fort Cassin beds of the Champlain basin (one 

 of the latter also occurring in the west and one at Lexington Va.), 

 the seventh, E. undatus, is a Black river limestone form of the 

 northeastern Mississippian sea (Watertown) and perhaps of the 

 Champlain basin,^ and the eighth, E . p 1 i c a t u s , Whiteaves, a 

 Galena-Trenton limestone form from the Lake Winnipeg region. 



As Whiteaves has lately [1903, p. 163] stated that the true 

 Inachus undatus of Emmons has been found only in the 

 Black river limestone at Kingston Ont. (Mississippian sea) and the 

 forms currently referred to that species from the Province of Quebec 

 are either Plectoceras halli (Foord) or undetermined or un- 

 described forms, it is probable that the Lituites undatus of 

 White is referable to one of the latter species and Eurysto- 

 mites undatus is restricted to the Mississippian sea. 



The western type of E. undatus has been described by Hall 

 as a separate variety, viz, E . undatus var. occidentalis. 

 It is stated by Clarke, that this has a more general distribution than 

 the eastern form and the correlation table of the Minnesota report 

 lists it as occurring in the Stones river group (Lowville limestone). 



A fact that is worthy of special notice here is the identity of the 

 single nautiloid yet found below the Black river-Trenton beds in the 

 west with our most common species of Eurystomites in the Fort 

 Cassin beds of the Champlain basin, viz, E , k e 1 1 o g g i , 

 [see p. 460] . There is, hence, no doubt that the genus Eurystomites 

 occupied already in Beekmantown time the Mississippian or epicon- 

 tinental American sea and persisted there into Trenton time. 



In summing up we may say that Eurystomites finds its principal 

 development in the Beekmantown formation of the Champlain basin 

 and extended in that period far south in the Appalachian trough, 

 northward into the Newfoundland embayment and also occupied 

 .the Mississippian sea ; that is, it held the American epicontinental 

 sea into Trenton time when it was carried by the Trenton encroach- 

 ment to Baffin Land, whence Schuchert [1900, p. 173] records an 

 Eurystomites ( p 1 i c a t u s Whiteaves ?) . 



^ See List of Champlain Upper Ordovicic Fossils, published or circulated by 

 Th. G. White in 1898. 



The "Lituites undatus" cited by P- E. Raymond from the 

 Chazy of Crown Point is probably a Plectoceras, of the group of 

 P. jason, since Eurystomites undatus is in the east strictly a 

 Black river form. 



