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ANALYSIS OF THE FAMILIES AND GENEBA OF THE LIVING 

 CEPHALOPODA, 



First Order. — Dibranchiata (Owen, 1832), 1 containing Section I., 

 Octopoda, and Section II., Decapoda. 



Section I. of First Order. — The Eight-armed Cuttles, Octopoda {Leach, 1817). 



Octopoda. — Body round, oval, or conical, furnished with eight arms. 

 Mantle united to the head by a broad band, sometimes strengthened by- 

 lateral ridges fitting into corresponding side furrows in the part adjacent 

 to the funnel. Fins generally absent. Eyes fixed. Arms with one or 

 two rows of suckers, which are without horny margins and not on pro- 

 minences (pedunculated). Shell generally absent, sometimes internal 

 and rudimentary, sometimes external and developed. Nine Genera, 

 Eledone, Bolitaena, Cirroteuthis, Octopus, Scseurgus, Pinnoctopus, Philo- 

 nexis, Tremoctopus, and Argonauta, separated into three divisions (A. B. C.) 

 according to the connection of the mantle with the head. 



I. — Division A.— Mantle without side ridges ; arms united by a mem- 

 brane, Octopidee, D'Orbigny, 1845. Six Genera, Eledone, Boli- 

 taena, Cirroteuthis, Octopus, Scaeurgus, and Pinnoctopus. 



(a.) One row of suckers on the arms. 



1. Eledone, Leach, 1817 Body oval, the arms united at their base 



= Eledon, Cuvier, 1817. by a membrane, no fins. 



= Moschites, Schneider, 1835. 



2. Bolitama, Steenstrup, 1858 Body oval, arms united at their base by a 



membrane, no fins, suckers small. 



3. Cirroteuthis, Eschricht (1836) 1838. Body round the arms united their whole 



= Sciadelphorus, Reinh, 1846. length by a membrane, hairs alternate 



= Bostrychoteuthis, Agassiz, 1847. with the suckers, transverse fins. 



($.) Two rows of suckers on the arms. 



4. Octopus, Lamarck, 1799 Body oval, the arms long, united at their 



= Cistopus, Gray, 1849. base by a membrane, no fins. 



5. Scaeurgus, Troschel, 1857 Body oval, the arms short, no fins. 



6. Pinnoctopus, D'Orbigny, 1845 Body oval, the arms united at their base 



by a membrane, lateral fins. 



II. — Division B. — Mantle with side ridges, two of the arms of greater 



length than the rest, suckers in two rows. Philonexidse, D'Orbigny, 

 1845. Two Genera, Philonexis and Tremoctopus. 



7. Philonexis, D'Orbigny, 1839 The arms not united by a membrane. 



8. Tremoctopus, DelleChiaje, M.S., 1835 Some, or all of the arms united by a 



membrane. 



III. — Division C. — Mantle supported by a single ridge, body of female 



enclosed in a shell, with two of the arms much expanded at their 

 extremities, male shell-less. Argonautidae, Reeve, 1841. One, 

 genus, Argonauta. 



9. Argonauta, Linne', 1758 The shell thin, involute, single chambered 



= Ocythoe, Rafinesque, 1815. not moulded upon the animal. 



1 The name which follows each order, etc., is that of the author who described the 

 order, or family, or genus ; the figures are the dates of publication of the order, etc. 



