48 NORTH AMERICAN INDEX FOSSILS. 



14. 0. modestum Ruedemann. Ordovicic. 

 Slender, nearly cylindrical, increasing at the rate of i in 30 mm., 



5 camerse in about 10 mm. in adult ; living chamber long, with one 

 or several constrictions; siphuncle small, centren; surface with 

 exceedingly fine, regular, growth lines only. 



Chazy (C6) of the Lake Champlain region. New York and 

 Vermont. 



15. 0. recticameratum Hall. Ordovicic. 

 More rapidly expanding than preceding, somewhat deeper 



camerae (4 in 10 mm.) and septa somewhat angular. 



Lowville (Upper Chazy an) of Mohawk and Black River 



Valleys. 



16. 0. multicameratum Emmons. (Fig. 1245.) Ordovicic. 

 Camerse more irregular in depth varying from one fourth to 



one half the diameter. 



Lowville of New York; Stones River of Cincinnati region of 

 Tennessee; Stones River, Black River and Trenton of Minnesota. 



17. 0. junceum Hall. (Fig. 1246.) Ordovicic. 

 More slender and more gently tapering than preceding ; siphuncle 



centren; septa thin, one third to one fourth diameter apart, 

 strongly arched, more closely ' arranged towards the deep living 

 chamber. 



Stones River and Black River and Trenton of Minnesota and 

 Cincinnati region; Trenton of New York and Canada. 



18. 0. amplicameratum Hall. (Fig. 1247.) Ordovicic. 

 Larger than the preceding; septa strongly arched; about one 



third diameter apart; siphuncle excentric. 



Black River and Trenton of Canada; Trenton of New York, 

 Tennessee and Minnesota (?). 



19. 0. (Geisonoceras) shumardi Billings. Ordovicic. 

 Small, septa separated by nearly half a diameter; siphuncle 



somewhat larger proportionally and less excentric than in the pre- 

 ceding which it otherwise resembles. 



Chazy of Mingen Island and New York (Div. Bg). 



20. 0. (Geisonoceras?) sociale Hall. (Fig. 1248.) Ordovicic. 

 More rapidly expanding than preceding; septa deeply concave, 



