112 MR. OWEN’S DESCRIPTIONS OF 
of the head; the greatest breadth of the body is 4 lines ; the breadth of the head, in- 
cluding the eyes, is half an inch. Of the eight arms which radiate from the anterior 
part of the head, the first or dorsal pair is the longest, as is the case in many species 
of Octopus ; the second pair is nearly. the same length as the first ; the third pair, which 
is commonly the longest in the Decapods, is here scarcely half the length of the first ; 
the fourth pair is nearly two thirds the length of the first. 
The musculo-membranous web which is usually extended between the bases of all 
the arms in the Octopi, is in this species developed to the ordinary extent between the 
four dorsal arms only : the webs between the second and third, and the third and fourth 
arms are very short; that between the fourth pair is wanting. From this peculiarity I 
propose to name the species Octopus semipalmatus. The suckers are sessile, and are 
arranged in a double close-set alternate series on the margins of the internal surface of 
the arms, with a broader interspace than is usually observed (figg. 12, 13. Pl. XXI.) 
The eyes are of proportionally large size, and present a dark colour, in consequence 
of the pigment shining through the sclerotic coat. The sclerotic is perforated by a cir- 
cular aperture in the usual situation ; and as the dermal cornea, which covers the ante- 
rior part of the sclerotica in the common Poulp, is absent in this species, the capsule of 
the crystalline lens is exposed, as in the Nautilus, to the sea-water. The funnel has the 
usual exterior form: it is without a valve; but at the sides of its base there is a struc- 
ture approaching to the articulation by which it is united to the mantle in the Decapo- 
dous tribe of Cephalopods. Immediately above the insertion of each lateral pillar there 
is a small transverse crescentic ridge which rests upon a similar ridge projecting from 
the side of the mantle (see a, 6, fig. 13. Pl. X XI.) ; neither of these prominences however 
is supported by cartilage, as in the Decapoda. In the Octopus catenulatus there is a 
similar structure, but the projection on the mantle is shorter and more prominent ; in 
the Argonauta the articulation of the sides of the funnel is still more complete, and is 
constant in all the known species of that genus’. 
With respect to the anatomy of this small Cephalopod it may be observed, that in 
the presence of a crop, in the lateral insertion of the gullet into that receptacle, in the 
muscular stomach, the spiral laminated bag, and the folded intestine, it accords with 
the generic type of structure presented in the common Poulp (Octopus vulgaris, Cuv.). 
The ink-bag is similarly buried m the anterior part of an undivided large liver : the biliary 
ducts are without glandular appendages : the follicles appended to the branchial divisions 
of the vena cava, are elongated, and hang from the exterior of the vessels ; the branchial 
hearts are without fleshy appendages; the branchie are connected by membranous 
bands to the sides of the mantle ; the branchial amine present a zig-zag folding, as in 
' The preceding examples of the infundibular joints in the genus Octopus diminish the value of that cha- 
racter as distinguishing Ocythot from Octopus. See Dr. Leach’s account of Ocythoé Cranchii,—Phil. 
Trans. 1817, p. 295. 
