MOLLUSCA. CEPHALOPODA 287 



Silurian. Orthoceras, Cyrtoceras, Actinoceras, G omphoceras, 

 Phragmoceras, Trockoceras, Ascoceras, Ophidioceras. 



Devonian. Nautiloidea : — Orthoceras, Cyrtoceras. Animonoi- 

 dea : — Clymenia, Bactrites, Mimoceras, Anarcestes, Tornoceras. 



Carboniferous. Nautiloidea : — Orthoceras, Cyrtoceras, Actinoceras, 

 Poterioceras, Discites, Vesti nautilus, C&lonautilus, Pleuronautilus, 

 Temnocheilus. Ammonoidea : — Glyphioceras, Gastrioceras, Pro- 

 lecanites. 



Permian. Nautiloidea : — Orthoceras, Temnocheilus. Ammo- 

 noidea : — Medlicottia, Cyclolobus. 



Trias. Nautiloidea : — Nautilus, Orthoceras. Ammonoidea : — 

 Pinacoceras, Ceratites, Trachyceras, Ptychites, Arcestes, Cladiscites, 

 Monophyllites, Rhacophyllites. Dibranchia : — Aulacoceras, Atrac- 

 tites, Phragmoteuthis. 



Lias. Nautiloidea : — Nautilus. Ammonoidea : — Phylloceras, 

 Lytoceras, Psiloceras, Arietites, JEgoce?'as, Liparoceras, Oxynoticeras, 

 Amaltheus, Schlotheimia, Harpoceras, Hildoceras, Cosloceras, Dacty- 

 lioceras. Dibranchia : — Belemnites, Xiphoteuthis, Geoteuthis. 



Oolites. Nautiloidea : — Nautilus. Ammonoidea : — Ludwigia, 

 Leioceras, Haploceras, Stepheoceras, Macrocephalites, Cardioceras, 

 Quenstedtoceras, Perisphinctes, Peltoceras, Aspidoceras, Parkinsonia, 

 Cosmoceras. Dibranchia : — Belemnites, Belemnoteuthis, Acantho- 

 teuthis. 



Lower Cretaceous. Nautiloidea : — Nautilus. Ammonoidea : — 

 Macroscaphites, Hamites, Holcostephanus, Desmoceras, Parahoplites, 

 Douvilleiceras, Crioceras. Dibranchia : — Belemnites. 



Upper Cretaceous. Nautiloidea : — Nautilus. Ammonoidea : — 

 Hamites, Turrilites, Baculites, Desmoceras, Pachydiscus, Hoplites, 

 Acanthoceras, Scaphites, Schloenbachia. Dibranchia : — Belemnites, 

 Belemnitella, Actinocamax. 



Eocene. Nautiloidea: — Nautilus, Aturia. Dibranchia : — Belo- 

 sepia, Beloptera, Spirulirostra. 



