132 PEOF. OWEN ON NEW AND EAEE CEPHALOPODA. 



pretty closely resembling, in average size and in the extent of the basal interbrachial 

 membrane, the common Poulpe {Octoims vulgaris) of our own shores. As, however, the 

 acetabular character seems to be of equal distinctive value to that of the opposite extreme 

 connotive of Uledone \ I regard the present species as the type of a genus, the character 

 of which has suggested the name above given. 



The following are dimensions of my specimen of Tritaxeojnis : — in. lin. 



Length of the body 3 9 



,, of the head to the division of the fleshy bases of the arms . . 2 

 „ of the animal to the free margin of the interbrachial web . 8 



Breadth of body at its hinder half 2 7 



,, of head, across the eyes 2 3 



The arms differ as to length in the order characteristic of the second section of the 

 " Poulpes " in D'Orbigny's monograph ^, and graduate in the special manner seen in 

 Octopus vulgaris : viz., the "third" arm counting from the dorsal (i) to the ventral (^) pair, 

 being the longest, the "second" arm is but little longer than the "fourth," and the "first" 

 is the shortest. The length of the " third" arm in the specimen figured (PL XXIII. 3) 

 is 1 foot 11 inches, that of the first (ib. 1) being 1 foot 2 inches. The basal thickness 

 of the fleshy part of the third arm is 1 inch; and this dimension does not diminish in the 

 same degree as does the length in the shorter arms. The extent of the basal webs, a, a, 

 uniting the arms from the base to the middle of the free margin, is 2^ inches between 

 the second (2) and third (3) arms, and 1^ inch between the first (1) and second (2) 

 arms. The proportional magnitude of the " cephalic crown," formed by the arms and 

 their webs, to the body, in Tritaxeopits cornutus, is as great as in Octoims vulgaris ^ 



The integument of the body is beset with scattered wart-like prominences, chiefly on 

 the dorsal aspect ; and, of these, four or five of the largest aff'ect a longitudinal 

 disposition. 



The tegumentary eyelids are well developed ; and each supports prominences on the 

 upper border, of which the two anterior are so large and pointed as to simulate horns, 

 whence the nomen triviale of the present species. 



The fleshy stem or basis of the arms is, in transverse section, rather semicircular 

 than trihedral. The flat side supports the suckers. They begin at the brachial 

 basis (ib. flg. 2) in a single series, and, alternating in position after the third or 

 fourth, assume the ordinary biserial arrangement ; then the two series diverge after 

 ' Dr. Gray, in the ' Catalogue of the MoUnsoa in the Collection of the British Museum,' Part i. (12mo, 1849) 

 ■ — Cephampoda antepebia — defines the genera Octopus, Cistopiis, Pinnoctopus, as having " arms with two rows 

 of cups " (p. 4), in contradistinction from Eledona and Cirroteuthis, which have " arms with one row of cups." 

 ^ " B. Bras lateraux les plus longs " (Histoire naturelle generale et particuliere des Cephalopodes Aoe'tabu- 

 liferes,' &c., fol. 1839, p. 17). 



' M. d'Orbigny remarks on this character of " la couronne :" — " Son volume extraordinaire distingue de 

 suite I'Octopus vulgaris des autres espeoes " (op. cit. p. 28). It applies, however, more precisely, to the female 

 of the species ; and the subject of PI. XXIII. fig. 1 of the present memoir is of this sex. 



