140 
M. SASAKI. 
is in the middle, the height being much greater than tlie thickness of these 
arms. The fourth pair is quadrangular along the whole length, and has a 
broad web along the dorsal outer edge. The ventral protective membranes 
of the second and third pairs, are a little broader than the length of the 
suckers, but the dorsal membranes of these arms are about equal to their 
length. Both the protective membranes of the remaining arms are much 
narrower than all the preceding ones. 
The arm-suckers are semicircular and arranged in two series. The size 
does not show any sexual dimorphism, but varies in the different arms of 
each individual, the suckers of the second and third pairs of arms being 
much larger than those of the first and fourth pairs: in a female of 208 mm. 
mantle-length, 3.2 mm. in I pair of arms, 3.5 mm. in II and III, 2.7 mm. in IV. 
The horny rings of the arm-suckers have several distinct teeth along the 
distal margins ; the proximal margins project slightly, forming a narrow 
border of smooth edge ; the shape of the teeth varies in the different suckers : 
in the third pair of arms, the horny ring of one of the suckers in the second 
row from the base has ten somewhat pentagonal teeth thickly arranged, of 
which the lateral ones are much broader than the median and are very ob- 
lique ; the horny ring in the sixth row has eight strong acute conical teeth, 
but of these the marginal ones are both obliquely quadrangular and much 
broader than the others ; besides these, there are found five flat semicircular 
or quadrangular supplemental teeth, alternating thickly with the preceding 
ones, (PI. IV, fig. 3a) ; the horny ring of tlie fifteenth row has eight slender 
and acute teeth, of which the marginal ones are a little broader than the 
remaining ones, and of which the interdental spaces are a little broader than 
those of the fore-going suckers (PI. IV, fig. 3c) ; the horny rings of the re- 
maining suckers, except those more distal than the fifteenth row, show a 
character intermediate between those above described. The denticulation 
of all the suckers more distal than the fifteenth row resembles closely that 
of the fifteenth row, but the number becomes less towards the extremities 
of the arms. 
