•§> 201. THE CEPHALOPHORA. 225 



Family : Tectibranchia. 



Genera : Gasteropteron, Umbrella, Doridium, Bulla, Bullaea, Aplysia, 

 Notarchus, Dolabella, Pleurobranchus, Pleurobranchaea. 



SUB-ORDER III. TUBICOLAE. 



Animals which are enclosed, together with their branchiae, in simple 

 slightly curved or irregularly flexuous tubes. 



Family : Cirribranchia. 

 Genus : Dentalium. 



Family : Tubulibranchia. 

 Genera : Vermetus, Magilus. 



SUB-ORDER IV. PECTINIBRANCHIA. 



Branchiae in a special cavity situated at the anterior part of the back. 

 Shell regularly spiral. 



Family: Sigaretina. 



Genus : Sigaretus. 



Family : Purpurifera. 



Genera : Buccinum, Harpa, Cassis, Purpura, Ebicrnea, Terebra. 



Family: Canalifera. 

 Genera : Murex, Struthiolaria, Tritonium, Turbinella, Fasciolaria. 



Family : Alata. 

 Genera : Strombus, Rostellaria, Pterocera. 



Family : Cerithiacea. 

 Genus : Cerithium. 



Family : Volutacea. 

 Genera : Valuta, Oliva, Mitra. 



Family : Involuta. 

 Genera : Cypraea, Ovula. 



Family: Conoidea. 



Genus : Conus. 



Family: Trochoidea. 



Genera : Scalaria, Turbo, Trochus, Phasianella, Rotella, Littorhia, Jan- 



thivM. 



Family : Neritacea. 

 Genera : Natica, Nerita. 



