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X. Descriptions of some neiv and rare Cephalopoda. (Part II.) 

 By Professor Owen, C.B., F.B.8., F.Z.S., &c. 



Eeceived 2nd March, read 20t]i April, 1880. 



[Plates XXIII.— XXXV.] 



Since the publication of the paper " On some new or rare Ceplialopoda" in the 

 second volume of the 'Transactions of the Zoological Society' (1842, p. 103) \ I have 

 not omitted any opportunity of acquiring and promoting the acquisition of specimens of 

 that class, and now submit to the Society a selection of such materials as seem worthy 

 of forming a second contribution on the subject. 



Class CEPHALOPOBA, Cmiex^. 



Order DIBEANCHIATA, Owen 3, 



Suborder Octopoda, Leach *. 



Genus Tritaxeopus, Owen ^. 



Species Tritaxeopus cornutus, Owen. (Plate XXIII.) 



The ' Poulpes,' or eight-armed Cephalopods, as a rule, bear their suckers in two rows 

 along each arm. But, however numerous and seemingly " opposite " in arrangement, 

 they are " alternate ;" and this order becomes more obvious as the suckers are fewer 

 in number and further apart on the acetabuliferous surface. There are also species in 

 which the zigzag course becomes so opened out that the suckers appear to be in a single 

 series, at first along the distal half of the arm, as in Octopus lechenaultii ; and finally, 

 with a feeble indication of the zigzag at the basal part, the suckers curve in a linear 

 course to the end of the arm, giving the character on which the generic group Eledone " 

 is founded. 



Other genera or subgenera of the Octopoda have been based on marginal extensions 

 of the arm -membranes [Cistopus, Pinnoctopus, &c.) ; but I have hitherto failed to find 

 a notice of any Octopod characterized by having the brachial acetabula in three recog- 

 nizable series along more or less of each arm. 



This, however, is the constant character of an Australian species in other respects 



' Communicated February 23rd, 1836. See ' Proceedings ' for that year. 



2 " Ccphalopodes," Tableau elementaire de I'Histoire Naturelle des Animaus, 8vo, an 6 (1797), p. 378. 



^ Memoir on the Pearly Nautilus, 4to, 1832, p. 56. 



* Zoological Miscellany, iii. (1817) ; " Triius Octopoda;' Trans. Zool. Soc. ii. (1841), p. 129. 



° rpeZs, three; rcUis, rank ; ttoJs, foot. "^ eXe^wi'j), Arist. ; Eledone, G\\v.; Eledon, Lea.ch, 



VOL. XL — PARTY. No. 1. — June, 1881. z 



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