314 
THE VOYAGE OF H.M.S. CHALLEHGEE. 
slightly posterior to the lateral tentacle (next the median). In regard to the structure 
of the dental apparatus (Fig. 70), this minute form differs from the previous species in 
the greater breadth of the posterior plate of the maxilla, and the narrower aud more 
distinctly curved anterior region. The posterior spathulate appendages approach the 
shape of a double cocoa-nut. The left great dental plate has eleven teeth, and the 
same number appears on the right. Moreover, the first series on the left (about three) 
does not show the separation and special development characteristic of the former species. 
Such a divergence is not altogether due to age. The left lateral paired plate appears 
to have about eight, while the left unpaired has twelve distinct teeth. The right 
lateral shows about eight, but this and the left paired could not be distinctly enumerated. 
The mandibles (Fig. 71) have the cutting surface less developed, presenting a simple 
convex edge, with a notch at the external angle. The longitudinal blackish band on 
each side of the fissure is much more distinct as well as more evidently symmetrical. 
It bends inwards anteriorly to a thick angle, and then proceeds backward with a 
slight curve. The ventral dental surface forms a broad V. 
The bristles of the first foot seem to be nearly related to those of Notliria som- 
hreriana. In the present minute form the bristles possess broader wings, and the 
tips of the long hooks differ in having shorter forks. 
The structure in transverse section corresponds with the plan of the typical 
form, though the ventral muscles bulge downward on each side of the median line. 
The size of the nerve-cords would indicate that the specimen is young. The bod}' 
is less flattened than in Nothria conchylega, and the muscular environment of the 
ventral longitudinal muscles less distinct. The neural canal occupies the same 
position. 
Nothria abranchiata, n. sp. (PI. XL. figs. 10, 11, 12 ; PI. XXIa. fig. 27 ; PI. XXIIa. 
figs. 1-3). 
Habitat. — The larger examples were trawled at Station 156 (Antarctic region), 
February 26, 1874; lat. 62° 26' S., long. 95° 44' E.; depth, 1975 fathoms; surface 
temperature, 33° ’0 ; sea-bottom. Diatom ooze. 
Also at Station 335 (in the middle of the Atlantic, north of Tristan da Cunha), 
March 16, 1876; lat. 32° 24' S., long. 13° 5' W.; depth, 1425 fathoms; bottom 
temperature 37°'0, surface temperature 73°‘5 ; sea-bottom, Pteropod ooze. 
The species a23pears to be of considerable size, the breadth of the last-mentioned 
example being fully 5 ‘5 mm. across the anterior feet. 
The head (PI. XL. fig. 11) agrees generally with that of Nothria conchylega, but 
the frontal tentacles are notably shorter. The median and other tentacles, again. 
