NIAGARA FALLS AND VICINITY 



21 



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 Nautiloidea, 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. 



:r NAUTILOIDEA 



Genus orthoceras Breyn 



[Ety.: o/z^/ov?, straight; -/Jpa^:, horn] 



\ \ f i'^73^- Dissertatio physica de polythalamiis) 



Fig. 146 oi^ti^ras Shell a straight conic tube, with a large body 

 muitiseptum chamber and numerous air chambers, separated by 



convex septa. Sutures simple, at right angles to 

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

 central, or eccentric, cylindric or sometimes 

 w^idening in the chambers. Surface smooth or 

 variously ornamented by transverse or longitud- 

 inal striae, or by annulations. 



Orthoceras muitiseptum 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. Y. 2:293, pi. 64, 65) 



Distinguishing characters. Strong annulations; 

 moderately strong longitudinal lines which node ^S^^J ^'enSf por- 



, ,. r , 2_ • iTi." tiou showing shell of liv- 



the annulations, ime transverse striae; elliptic ing chamber and section- 

 ed camerae (after Bar- 



cross-section; subcentral siphuncle. rande) 



Found in the Clinton limestone lenses in the Rome, Watertown 

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



