SYSTEMATIC INDEX 
OF THE 
FAMILIES, GENERA, AND SUBGENERA. 
Page 
Family LITUITID.E 1 
Lituites 1 
Ophidioceras 8 
Family TROCHOCEllATID.E 14 
Trochoceras 14 
Family XAUTILID.E 43 
Trocholites 43 
Gyroceras 53 
8. g. Aipoceras 68 
8. g. Trigonoceras 70 
Hercoceras 74 
Barrandeoceras 77 
Discites 86 
8. g. Phacocera8 98 
Ephippioceras 100 
Coelonautilus 105 
