Xll 
TABLE OF CONTENTS. 
PTEROPODA, of the Palaeozoic formations — ( Continued ): pagk. 
Hyolithes: Historical sketch ......... 191-193 
Distribution of species. 193-195 
Descriptions of species .......... 195-202 
Clathroccelia : Generic features and description of species .... 203, 204 
Conularia : Historical sketch ......... 205-207 
Geological distribution .......... 207, 208 
Descriptions of species. 208-216 
CEPHALOPODA, of the Palaeozoic formations ....... 217-478 
Orthoceras : Historical sketch ......... 217-226 
Subgeneric, stratigraphical and geographical relations .... 226-230 
Distribution of species. 230-232 
Orthocerata of the Schoharie grit ........ 233-264 
Orthocerata of the Upper Helderberg limestone ..... 264-271 
Orthocerata of the Hamilton group ........ 272-304 
Orthocerata of the-Portage group \ ...... . 304-308 
Orthocerata of the Chemung group ........ 308-314 
Bactrites: History, and description of species.315-317 
Gomphoceras: Historical sketch, distribution and generic relations . . 318-320 
Descriptions of species. 321-353 
Cyrtoceras : Generic reference and historical sketch. 354, 355 
Gyroceras : Relations of species and historical sketch .... 358-360 
Cyrtoceras : Descriptions of species ........ 360-373 
Gyroceras : Descriptions of species. 373-389 
Trochoceras : Historical sketch and distribution . . . . . . 390, 391 
Description of species. 392-403 
Nautilus: Historical sketch. 404-406 
Description of species. 407-424 
Nautilus, subgenus Discites : Descriptions of species. 425-430 
Goniatites : Historical sketch.. 431,432 
Descriptions of species. 433-478 
ADDENDA ET CORRIGENDA.. 479,480 
INDEX. 481-492 
