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and sometimes a surrounding guard ; siphuncle ventral. 
Genera : Belemnites, Belemnitella, Acanthoteuthis, Belem- 
noteuthis, Szc, &c. 
Family F. Teuthidce. — Animal provided with fins or lateral 
expansions of the mantle, and an internal chitinous pen 
(gladius). Genera : Loligo, Gonatus, Sepioteuthis, Belo- 
teuthis, Geoteuthis, Cranchia, Sepiola, Loligopsis, Cheiro- 
teuthis, Histioteuthis, Onychoteuthis, Enoploteuthis, Omma- 
tostrephes, &c., &c. 
Section (2) Octopoda. — Animal possessing eight arms only, 
furnished with sessile suckers, gills attached by the stalk 
only. No shell, but the female Argonaut forms an external 
involute egg- capsule, which is not attached to the animal by 
any muscular connection. 
Family G. Octopodidce. — Internal rudimentary styles re- 
present the internal S'hell, fins usually absent, arms webbed at 
the base. Genera : Octopus, Pinnoctopus, Eledone, Cirro- 
teuthis, Philonexis, Scaeurgus, Bolitcena, &c. 
Family H. Ai-gonaididce. — Mantle supported anteriorly 
by a ridge on the funnel. The female, with the webbed 
extremities of her anterior arms secretes a white papery 
involute single chambered shell. 
Genus. — Argonauta. 
As to the phjdogeny of the Cephalopoda it may be said 
that little more than a guess could be made in the present 
state of our knowledge of their embryology, for absolutely 
nothing is known of the development of one whole order, 
the Tetrabranchiata, and as Owen has well remarked of the 
development of the cuttle-fish, there is no metamorphosu; ; 
the Cephalopodic character is manifested long before the 
parts of the embryo are completed." It may, however, be 
expected that light will be thrown on this difficult subject 
when the embryology of the Nautilus shall be discovered, 
and when palaeontologists have studied the fossil forms more 
