Fam. Cirrhoteuthidae. Tentacular filaments on either side of the suckers. Cirrhoteuthis, pallial sac prominent, fins large, pelagic. Opisthoteuthis, body flattened, with small fins, deep-sea. Vampyroteuthis, four fins. Palaeoctopus, fossil, Cretaceous.
Tribe 2. Trachyglossa.—Radula present. No fins.
Fam. 1. Amphitretidae. Arms united by membrane; funnel attached to mantle, dividing the pallial aperture into two. Amphitretus, pelagic.
Fam. 2. Alloposidae. All arms united by membrane; mantle joined to head by dorsal band and two lateral commissures. Alloposus, pelagic.
Fam. 3. Octopodidae. Arms long and equal, without membrane; hectocotylus not autotomous. No cephalic aquiferous pores. Octopus, two rows of suckers on each arm, British. Eledone, single row of suckers on each arm. Scaeurgus. Pinnoctopus. Cistopus. Japetella.
Fam. 4. Philonexidae. Hectocotylus autotomous; arms unequal in size; aquiferous pores on head and funnel. Tremoctopus, two dorsal pairs of arms united by membrane. Ocythoë, without interbrachial membrane.
Fam. 5. Argonautidae. Hectocotylus autotomous; no interbrachial membrane; extremities of dorsal arms in female expanded and secreting a shell; males very small, without shell. Argonauta.
Literature.—Use has been freely made above of the article by E. Ray Lankester, on Mollusca, in the 9th edition of this Encyclopedia. For the chief modern works, see Bashford Dean, “Notes on Living Nautilus,” Amer. Nat. xxxv., 1901; Arthur Willey, “Contribution to the Natural History of the Pearly Nautilus,” A. Willey’s Zoological Results, pt. vi. (1902); Foord, Cat. Fossil Cephalopoda in British Museum; Alpheus Hyatt, “Fossil Cephalopods of the Museum of Comp. Zoology,” Bull. Mus. Comp. Zool. (Cambridge, U.S., 1868); Jalta, “I Cefalopodi viventi nel golfo di Napoli,” Fauna und Flora des Golfes von Neapel, xxiii. (1896); Joubin, “Céphalopodes de l’atlantique nord,” “Céph. de la Princesse Alice,” Camp. sci. Albert Ier de Monaco, ix. (1895), xxii. (1900); Paul Pelseneer, “Mollusca,” in the Treatise on Zoology, edited by E. Ray Lankester.
(J. T. C.)