104 
AUSTRALASIAN ANTARCTIC EXPEDITION. 
This tentacular membrane, then, has the same topographical relations as the 
bundle of filamentous tentacles in other genera of the family, and it is unfortunate that, 
having only this single individual, I am unable to study its structure as fully as it 
deserves. 
Following the peristomium is the branchiferous segment (fig 3 . 12 L , 12 5, 126). Its 
dorsal surface is raised up as a transverse fold, which overhangs the peristomium and 
the posterior portion of the prostomium. It is continued downwards as an ordinary 
segment, but is without chsetse. This segment carries three pairs of gills, which arise 
in a transverse line; they are long, simple, sub-cylindrical, and grooved along the 
posterior margin. The base is more or less expanded, and each terminates on a bluntly 
rounded extremity. Of the six gills, however, only two remain entire : on the right 
side the most dorsal, which is 15 mm. long, and on the left side the middle gill, 
which is 10 mm. long ; the other four are represented by more or less of their basal 
region. f 
The two most dorsal gills are close together near the middle line; the base of 
each is produced outwards as a rounded ridge, passing obliquely outwards across the 
dorsum to end at the base of the second notopod. The second gill is immediately external 
to the first, and the third lies just above and in front of the first notopod. 
There are seventeen pairs of notopods, rather prominent lobes, carrying very long, 
stout, brown bristles ; the first notopod is on the third segment, which is much com¬ 
pressed between its neighbours (this is perhaps due in part to the contraction of the 
body) ; it is smaller than the rest, and carries fewer and shorter bristles ; the second is 
longer, the following increase in size, and the full development of the foot is attained at 
the sixth or seventh. 
The bristles, of which there is a considerable number in each notopod, arranged 
in a double or triple vertical series, are brownish in colour ; each is long, thick at the 
base, slightly curved, and produced into a very fine point ; there is single flange on the 
convex border.* 
The uncinigerous neuropods commence below the fourth notopod on the sixth 
body segment ; they are definite, wing-like, mobile organs, increasing in prominence pos¬ 
teriorly. In the thorax the neuropod has a long, vertical, uncinigerous margin, 
equalling in height that of the organ itself, but in the abdomen the neuropod is very 
convex superiorly, and has a short uncinigerous margin directed somewhat downwards 
(%• 129). 
The uncini are uniserial throughout the body, and number about eighty in 
the anterior feet. 
The uncinus (figs. 130, 131) has two rows of four nearly equal teeth, springing 
from a short, broad base, which is produced into a rounded lobe beyond the fourth 
*Treated as I treated the chaetae of Phyllocomus I find that the two lateral flanges are not present. 
