12 CEPHALOPODA. 
Orper I. DIBRANCHIATA. 
Suborder 1. Ocropopa.—Arms eight, sessile; no shell. 
(The so-called shell of the argonaut, is the ege-nest of the 
female.) 
Suborder 2. DecapopaA.—Ten arms, of which eight are sessile, 
and two o (longer) tentacular. Shell internal. 
SuporvDer Il. OCTOPODA. 
( Littoral.) 
Family Ocropopip®. Mantle supported by fleshy bands. No 
cephalic aquiferous pores. Arms subulate, elongated, more or 
less united by webs; their suckers sessile. 
( Pelagic.) 
Family TREMocTOPIDA (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 ArGconautipz. 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 ae 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. 
SuporDeER I]. DE CAPODA. 
A. Decapoda chondrophora. Internal shell horny. 
a. Myopside. Eyes covered by skin: mostly littoral species. 
Family Lonicinipm. Body rather long; buccal skin some- 
times armed with suckers; tentacular arms only partially retrac- 
tile ; fins lateral-terminal. Inner shell or gladius as long as the 
back. 
Family Speronip#. Body short; buccal skin without suckers ; 
tentacular arms completely retractile ; fins short, in the middle 
of the sides of the back. Gladius only about half as long as the 
body. First pair of dorsal arms hectocotylized in the male ; 
spermatophores attached around the orifice of the oviduct. 
b. Oigopside. Eyes naked: pelagic species. 
Family Crancuip#. 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 sean 
or without inner valve. Shell or gladius as long as the body, 
small, lance-like. 
Family CurroreutHip®. Body rather long; mantle supported 
on the body by cartilaginous ridges; sessile arms, long, partially 
