CHAPTER XXXIII. 



CEPHALOPODA. 



Systematic : 



I. TETRABRANCHIA, with two pairs of gills, two pairs of auricles, 

 two pairs of kidneys, external chambered shell and a large number 

 of tentacles round the mouth. Funnel consisting of two lobes ; with- 

 out ink-sac. 



1. Nautiloidea. 



2. Ammonoidea. 



II. DIBRANCHIA, with one pair of gills, one pair of auricles, one 

 pair of nephridia, with internal shell, the chambers of which are 

 seldom distinct (Spirula, Belemnites) often reduced or absent. Round 

 the mouth eight to ten arms. The two halves of the siphon united 

 to form a tube ; an ink-sac generally present. 



1. Decapoda, with ten arms. 



(A) Phragmophora. 

 Spirulidae. 

 Belemnitidae . 

 Belemnoteuthidae. 

 A canthoteuihidae . 



(B) Oigopsida. 

 Ommastrephidae. 

 Onychoteuthidae. 

 Cranchiidae. 

 Chiroteuthidae. 



(c) Myopsida. 

 Loliginidae. 

 Sepiolidtie. 

 Sepiidae. 



2. Octopoda, with eight arms. 



Cirrhoteuthldae, with fins. 

 Philonexidae, Tremoctopus, Philonems. 

 A rgonautidae. 

 Octopodidae, Octopus, Eledone. 



