NIAGARA FALLS AND VICINITY 



215 



Fig. 146 Orthoceras 

 multiseptum 



convex septa. 



chamber lodges the animal. The septa are pierced by a correspond- 

 ing series of holes, the walls of which are often prolonged backward 

 or forward into siphonal funnels, the whole constituting the siphuncle. 

 In the Xautiloidea, the sutures are, as a rule, simple or but 

 slightly lobed, and the siphuncle is commonly central or eccentric, 

 but seldom marginal, with the funnels generally di- 

 rected backward. The embryonic shell, or proto- 

 ) conch, is rarely retained. 



The shells of cephalopods are either straight 

 (more or less conic) or variously curved and coiled 

 to close involution. 



NAUTILOIDEA 



Genus orthoceras Breyn 



[Ety. : 6pG6<$, straight; zipas, horn] 



(1732. Dissert at io physica de poly thalamus) 



Shell a straight conic tube, with a large body 

 chamber and numerous air chambers, separated by 

 Sutures simple, at right angles to 

 the long axis of the shell; siphuncle central, sub- 

 central, or eccentric, cylindric or sometimes 

 widening in the chambers. Surface smooth or 

 variously ornamented by transverse or longitud- 

 inal striae, or by annulations. 



Orthoceras multiseptum Hall (Fig. 146) (1852. 

 Pal.N. Y. 2:14, pi. 4 (bis)) 



Distinguishing characters. Cylindric, gradually 

 tapering; septa distant one sixth to one seventh 

 the diameter. 



Found in the upper Medina sandstone at Lock- 

 port, etc. (Hall). Probably also at Niagara. 



Orthoceras annulatum Sowerby (Fig. 147). 

 Orthoceras undu latum Hall (1852. 

 Pal.N. 7.2:293, pi. 64, 65) 



Distinguishing characters. Strong annulations; 

 moderately strong longitudinal lines which node 

 the annulations, fine transverse striae; 

 cross-section; subcentral siphuncle. 



Found in the Clinton limestone lenses in the Rome, Watertown 

 and Ogdensburg railroad cut above Lewiston. Also in the Roches- 





Fig. 147 Orthoceras an- 

 nulatum. Terminal por- 

 tion showing shell of liv- 



ii* , • uou snowing sneiioi iiv- 

 elliptlC jng chamber and section- 

 ed camerae (after Bar- 

 rande) 



