1 62 NEW YORK STATE MUSEUM 



FIG. 



21 Young individual, showing the longitudinal lines with marked 



distinctness. Natural size. Rochester (Arey collection) 



Kionoceras darwini Billings (sp.) 



(See plate II, fig. 6; plate 12, fig. 1-8) 

 Page 84 



22 Fragment of shell, showing both the longitudinal ribs and 



transverse lines. Rochester (Arey collection) 



Kionoceras medullare Hall (sp.) 



Page 86 



23 Fragment of shell, showing the ornament ; from a gutta-percha 



impression of a natural mold. Natural size. Lower Shelby 

 bed (N. Y. State Museum) 



Orthoceras trusitum sp. nov. 



(See plate 13, fig. 1-10) 

 Page 77 



25 Internal cast of a slightly curved individual with very closely 



arranged septa. Natural size 



26 Young individual, showing the smooth surface and the depth 



of the camerae. Natural size. Rochester (Arey collection) 



Orthoceras crebescens Hall 



(See plate II, fig. 2-5) 

 Page 80 



24 Internal cast of camerae and siphuncle of young specimen, 



referred with some doubt to this species. Natural size 



27 Septal view of specimen figured on plate n, fig. 2, showing 



the section of conch, position and size of siphuncle. Natu- 

 ral size 



28 Septal view of specimen figured on plate 1 1, fig. 3. Lower 



Shelby bed (N. Y. State Museum) 



