1 68 



FIG. 

 I 



NEW YORK STATE MUSEUM 

 PLATE 13 



A M Q) 



O © 



Orthoceras trusitum sp. nov. 



(See plate 10, fig. 25, 26) 

 Page 77 



Fragment preserving the longitudinally lineated surface 

 Internal casts, showing the numerous, shallow camerae and 



straight transverse suture lines 

 Young individual, showing the slenderness of conch 

 Internal cast, showing undulating septal sutures 

 Septum with excentric siphuncle 

 Broken internal cast, showing the depth of camerae and the 



tubular siphuncle 



7 Septum, showing the circular section of conch and subcentral 



location and relative size of siphuncle 



8 Section of specimen represented in fig. i, showing the rela- 



tively great thickness of conch 



9 Part of living chamber, showing longitudinal lineation 



! 



