PROF. OWEN ON NEW AND RARE CEPHALOPODA. 157 
between a pair of suckers, taken at the basal attachment of their peduncles, is 2 inches, 
where they are widest apart. The greatest width of the acetabuliferous tract within 
the marginal folds is 33 inches. 
The section of the basal part of the arm shows the muscular mass to be divided by a 
thin aponeurosis (Pl. XXXV. fig. 1, d) into a peripheral (¢) and a central (/) portion. 
The peripheral muscular mass, ¢, at the inner side, a, shows a thickness of 6 lines; 
it is traversed by the main artery of the arm, g. This part of the peripheral mass 
gradually diminishes on each side to a thickness of 2 lines, and then as gradually 
increases to 4 lines at ¢ ; when, bending in to the outer side of the arm, it thins off to 
half a line, the aponeurotic boundary coming there almost into contact with the outer 
integument. The transverse diameter of the inner muscular mass at the dorsal third 
is 2 inches 8 lines; at the ventral third it is 2 inches: and here the section shows the 
nerve, /, in a canal of 5 lines diameter, the nerve being surrounded by loose cellular 
tissue including venous channels. 
The cups gradually increase in size to the sixth or eighth, which has a diameter of 
three fourths of an inch; and here the acetabuliferous tract and its marginal folds 
show the dimensions given in fig. 2, Pl. XXXV. They begin very gradually to diminish 
beyond the basal ten or twelve inches of the arm. 
Of the large cups the peduncle is 7 to § millims. in length; its base is 5 millims. in 
breadth, and gradually contracts to 2 millims. before insertion. This is at the side of 
the base of the cup, where the cup is least deep; and here there is a depression for 
receiving the peduncle (Pl. XX XV. fig. 3). 
The base of the cup is 20 millims. in diameter ; it is slightly convex, shows a fleshy 
tint, which changes to a white aponeurotic appearance at the periphery; and this 
character of the exterior of the cup continues to the aperture, which is circular and 
10 millims. in diameter. From this aperture slightly projects the margin of the broad 
chitinous hoop lining the walls of the cavity. The bottom of the cup, 12 millims. in 
diameter, is soft, muscular, covered by a thin, transparent aponeurosis, and seems, by 
its size, to have been capable of assuming the shape requisite to act as a kind of piston, 
and by the vacuum so produced to cause outward pressure to aid in infixing the teeth 
of the denticulate free border into the surface to which the arm may have been applied. 
The suckers, as they extend along the arm, diminish in diameter in a greater degree 
than in depth, and the smaller acetabula make a nearer approach to the spheroid form 
(Pl. XXXIV. fig. 2); but each hangs bya proportionately long peduncle until they come 
to near the end of the series, where they show but 1 millim. diameter, passing out 
of sight at about 2 inches from the pointed termination of the there gradually attenu- 
ated arm. The basal cups of the same side or series occur at first at intervals of 24 
millims.; and as the longitudinal interval shortens, the transverse one increases to an 
extreme of 2 inches, then progressively diminishes with the diminishing size of the arm. 
The integument of the acetabuliferous tract shows a denser surface and paler tint 
2c2 
