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NEW YORK STATE MUSEUM 

 PLATE 13 



Orthoceras trusitum sp. nov. 



(Si-e plate 10, fig. 25, 26) 

 Page 77 



PIC. 



1 Fragment preserving the longitudinally lineated surface 



2 Internal casts, showing the numerous, shallow camerae and 



straight transverse suture lines 



3 Young individual, showing the slenderness of conch 



4 Internal cast, showing undulating septal sutures 



5 Septum with excentric siphuncle 



6 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 



