12 CEPHALOPODA. 



Order I. DIBRANCHIATA. 



Suborder 1. Octopoda. — Arms eight, sessile; no shell. 



(The so-called shell of the argonaut, is the egg-nest of the 

 female.) 



Suborder 2. Decapoda. — Ten arms, of which eight are sessile, 

 and two (longer) tentacular. Shell internal. 



Suborder I. 00 TO FOB A. 



{Littoral.) 

 Family Octopodid^. Mantle supported by fleshy bands. No 

 cephalic aquiferous pores. Arms subulate, elongated, more or 

 less united by webs ; their suckers sessile. 



(Pelagic.) 



Family Tremootopid^ (Philonexid^). Front of mantle sup- 

 ported by two cartilaginous buttons at the base of the siphuncle, 

 fitting into grooves on the inner side of the mantle. Aquiferous 

 pores on the back of the head. Suckers pedunculated. 



Family Argonautid^. Mantle supported by two buttons 

 fitting into grooves at the base of the siphuncle. The two upper 

 or dorsal arms (in the female only) expanding into velamenta 

 or broad webs at their extremity, from which an egg-nest (shell) 

 is secreted. Cups slightly pedicelled. A pair of aquiferous 

 pores at the upper hinder angle of the eye. 



Suborder II. DE APOD A. 



A. Decapoda chondrophora. Paternal shell horny. 



a, Myopsidse. Dyes covered by skin: mostly littoral species. 



Family Loliginid^. Body rather long ; buccal skin some- 

 times armed with sucfkers ; tentacular arms only partially retrac- 

 tile ; fins lateral-terminal. Inner shell or gladius as long as the 

 back. 



Family Sepiolid^. Body short ; buccal skin without suckers ; 

 tentacular arms completely retractile ; fins short, in the middle 

 of the sides of the back. Gladius onl}^ about half as long as the 

 bod}^ First pair of dorsal arms hectocotylized in the male ; 

 spermatophores attached around the orifice of the oviduct. 



b. Oigopsidae. Dyes naked : pelagic species. 



Family Cranchiid^. Body rounded ; mantle united to the 

 head by a cervical band, and upon either side connate with the 

 base of the siphon ; head small, with large eyes ; arms short ; 

 tentacles long ; siphon long, not fastened to the head, and with 

 or without inner valve. Shell or gladius as long as the body, 

 small, lance-like. 



Family CniROTEUTrnD^. Body rather long; mantle supported 

 on the body by cartilaginous ridges ; sessile arms, long, partially 



