152 PROF. OWEN ON NEW AND RARE CEPHALOPODA. 
veins, and valvular beginnings of the two aorte’. The proportionate size of the ventricle 
is the same which the mandibles bear to those in Onychoteuthis raptor. 
There seems no reasonable doubt, therefore, that we have in the subject of figure 6, 
Pl. XXXII. the chief part of the organs of circulation in Cook’s “great hook-armed 
Cuttle-fish.” The muscular part of this heart is thickest at its widest part, near the entry 
of the branchial veins, a, a, and gradually thins off to the fore and hind ends where the 
aortz, b, 6’, are sent off. The fasciculi of fibres are disposed in different planes, and decus- 
sate each other obliquely. The terminal aperture of each branchial vein is provided 
with a pair of semilunar valves, c. The origin of each aorta is guarded by two similar 
but smaller valves. The right branchial vein terminates on a plane anterior to the left, 
and slightly affects the regularity of the lozenge-shape of the heart. 
I have reserved the most obvious and certain-evidences of the genus and present rare 
and huge species to close such account of Enoploteuthis cookii as can now be con- 
tributed to the Cephalopodal chapter of Zoology. 
Fortunately part of one of the ordinary eight arms (Pl. XXXII. fig. 1) was rescued 
from the cooking-galley of the ‘Endeavour,’ and, with the few viscera above described, 
was put into spirits for the anatomist at home. A section has been taken, probably by 
Hunter, from the base of the portion transmitted. The circumference of this section 
(ib. fig. 3) is 44 inches. The transverse section fig. 2 gives the form and diameters 
of the present truncate end of the portion of arm fig. 1. The arm is somewhat 
compressed, ovate, narrowest where it supports the uncinate acetabula, a, a. Its sub- 
stance is mainly muscular. The integument is smooth and thin; there is no trace of 
ridge, duplicature, or production at either the line of the dorsal or of the acetabular 
surfaces, such as are seen in the vela of Ommastrephes ensifer. Both sections show the 
subcentral cavity, 0, for lodging the bloodvessels and a nerve; a much smaller cavity, ¢, 
near the interspace of the acetabula appeared to lodge a nerve only. The muscular 
fibres are mainly in two groups; the mass of the external longitudinal ones, d, is, in 
section, thickest at the acetabuliferous part, and gradually decreases to the opposite and 
larger end of the section. The transverse or radiating fibres, e, pass from the thin aponeu- 
rotic line, f, dividing their mass from that of the longitudinal ones, d, to the stronger 
aponeurotic wall, g, of the subcentral nervo-vascular canal; the fibres of a well-marked 
fasciculus, g, act more especially upon the acetabuliferous part of the arm, tending to 
retract it, and to strengthen or support the hooks when these are infixed in a prey and 
when they are acted upon by the flexor and other muscular fascicles working the move- 
ments and applications of the entire arm. The central two thirds of the general mus- 
cular mass is condensed, seemingly by a greater admixture of tendino-fibrous tissue than 
in the peripheral third: it suggests the idea of a flexible supporting or skeletal part of 
the arm. 
1 This was the ground of my determination of no, 903, in the ‘ Catalogue’ above quoted, p. 84. 
