THE CEPHALOPODA 343 
TRIBE 2. TRACHYGLOSSA. 
These are Octopoda with a radula and without true fins. 
Famity 1. AMPHITRETIDAE, Hoyle. The funnel is attached to the 
middle line of the mantle, dividing the pallial aperture into two. The 
eight arms are united by a membrane. Genus—Amphitretus, Hoyle ; 
pelagic. Famity 2. Attoposrpas, Verrill. All the arms united by a 
membrane. The mantle is joined to the head by a dorsal band and two 
lateral commissures. Genus—Alloposus, Verrill ; pelagic. FAMILY 3. 
Ocropopipak, @’Orbigny. Arms long and equal, without a true inter- 
brachial membrane. The hectocotylus is not caducous. No cephalic 
Fia. 301. 
Argonauta argo, Linnaeus, left side of the female. I, funnel; II, mantle; III, eye; IV, 
dorsal webbed arm. (After Verany.) 
aquiferous pores. Genera—Octopus, Lamarck ; the suckers in two rows 
on each arm; British. Eledone, Leach; a single row of suckers on each 
arm ; British. Scaewrgus, Troschel. _Pinnoctopus, d@Orbigny. Cistopus, 
Gray. Japetella, Hoyle. Famity 4, Pattonexipan, @Orbigny. Males 
and females naked. The hectocotylus is autotomous. The arms are un- 
equal in size but similar in the two sexes. Aquiferous pores are present 
on the head and funnel. Genera—Tremoctopus, Delle Chiaje ; the two 
dorsal pair of arms are united by a membrane. Ocytho?, Rafinesque ; 
without an interbrachial membrane (Fig. 287). Faminy 5. ARGo- 
NAUTIDAE, Cantraine. The hectocotylised arm autotomous. The ex- 
tremities of the dorsal arms are enlarged in the female (Fig. 301), and 
secrete a shell in which the body is contained. The males are very small 
and naked. Genus—-Argonauta, Linnaeus. 
