446 MOLLUSCA. 



Fam. 1. Cirrhoteuthidae. Arms united by a membrane and carrying on each 

 side of the suckers filamentous appendages ; radula absent ; deep water. Cirrho- 

 tcuthis Eschricht. 



Fam. 2. Amphitretidae. Mantle fused with funnel in median line, leaving 

 two openings into mantle-cavity. Amptiitrctus Hoyle. 



Fam. 3. Octopodidae. Arms alike, more or less webbed ; often without fins. 

 Octopus Cuv. poulpe ; Scaeurgus Trosch. ; Elcdone Leach; Pinnodopus d'Orb., 

 with fins ; Alloposus Verrill. 



Fam. 4. Argonautidae. Female with a unil ocular spiral shell (Fig. 335) ; 

 males very small ; hectocotylized arm autotomous (Fig. 355). Argonauta L., 

 the paper-nautilus. 



Fam. 5. Philonexidae. Hectocotylized arm autotomous ; other arms all 

 alike in the two sexes ; large aquiferous pores near the head and funnel. 

 Philonexis d'Orb.; Tremoctopus Delle Chiaje. 



