316 
THE VOYAGE OF H.M.S. CHALLENGEE. 
In the older forms a dark pigment-line runs along the external and posterior borders, 
which are likewise considerably thickened by deposition of calcareous material. In the 
largest example the anterior margin of the mandibles is nearly transverse and much 
truncated, probably either from wear or injury. 
The two segments following the buccal differ from the succeeding, in so far as the 
ventral cirri have been less modified, the somewhat lobulated cirrus in each being very 
readily distinguished from the flattened scute on the third foot. 
The first foot differs from that of Nothria conchylega in being much shorter. It 
is thus less conspicuous in its anterior projection. The flattened posterior lamella so 
characteristic of the common species is absent. The blunt hook-shaped bristles (PI. 
XXIa. fig. 27) are much larger, and the terminal curve less abrupt. The tip has a 
blunt hook and a short process beneath. This foot, as in the ordinary form, bears a 
shorter dorsal cirrus than in the next segment. The ventral cirrus, again, is represented 
by a shorter and more globular process than in the European species, the accessory 
inner cirrus (close to the mouth) being also much shorter and broader. The other 
dorsal cirri anteriorly appear to be larger and longer, wdiile the ventral are somewhat 
less. The disc-like processes are better marked. The bristles of the first foot are 
imperfect in the specimen from Station 335. 
A characteristic feature of this deep-sea form is the much greater length of the 
bristles, which project boldly on each side. Moreover, no branchiae are present. 
Each foot (PI. XL. fig. 12) has generally about three long straight dorsal bristles 
with rather short and slender tips (PI. XXIIa. fig. 1), and a number of small brush- 
shaped forms, the extremities of which are curved so as to resemble a funnel with a 
spinous edge. Interiorly is a group (generally five) of more slender bristles with wings 
(PI. XXIIa. fig. 2). A single long hook (PI. XXIIa. fig. 3) occurs at the tenth foot, 
and a pair subsequently. The tip is deeply bifid, and the inferior fang slightly exceeds 
the superior in size. Lastly the foot, which is on the whole thicker than in Nothria 
conchylega, is supported by four spines. 
Posteriorly the bristles diminish in strength, while the hooks are somewhat stouter. 
The tail is terminated by two long filiform cirri. 
The antarctic tubes are somewhat flexible, the outer surface being coated with 
greyish mud (Diatom ooze), and strengthened with specimens of a long, moniliforra, 
brownish, arenaceous Foraminifer, which is chiefly attached to the sides, after the manner 
of the large glassy spicules observed in Nothria somhreihana. A large Zoanthus and a 
fragment or two of micaceous stone are also present. The chitinous lining of the tube is 
easily torn. 
The tube from the dej)ths of the Atlantic (PI. XL. fig. 10) measures about 100 mm. 
in length, and is composed of a thickish and rather friable secretion, coated with greyish 
foraminiferous mud, strengthened by spatangoid spines (which project outwards on each 
