4 SIR CHARLES ELIOT. 
The majority of the forms certainly referable to Tritonia are inhabitants of the cold or 
temperate seas, but the ‘Siboga’ expedition found two species in the Malay Archi- 
pelago. From the southern seas are recorded besides the present species 7. pallida 
Stimpson (Cape of Good Hope), 7. incerta Bergh (New Zealand), 7. appendiculata Eliot 
(South Orkneys), 7. (Candiella) australis (South Chile). The animal described as 
Microlophus poirieri, by MM. A. T. Rochebrune and J. Mabille in the “ Mission 
Scientifique du Cape Horn,” 1882-3, Vol. VL, p. 11-12 and plate 6, la and 1b., is 
probably a Tritonia. 
1. TRITONIA CHALLENGERIANA (JUV. 2). 
Bergh, Chall. Rep. Nudibr. (1884), p. 45. 
One specimen labelled ‘19, iii. 02, W.Q. (50), 10 Fath.” It is well preserved and 
of a uniform pale yellow colour, probably due to the preserving fluid. 
The animal is 29 mm. long, 9 broad, 7°5 high; not much tapering until quite the 
end of the body. The back is flat, not arched, almost smooth except for a few scattered 
minute tubercles. The foot is 5 mm. broad, rounded in front, and not grooved. 
Posteriorly, it is expanded into a sort of disc, but this may be a distortion. 
The margins of the back and the foot are marked by very distinct lines, a little 
lighter in colour than the rest of the body, but not projecting much. There are eleven 
branchize on each side, and an additional tubercular prominence on the left. On the 
right side the largest are the fourth, sixth and seventh; on the left the fourth, fifth 
and seventh. These plumes are about 3 mm. long and 2 mm. wide at the 
top. They are not foliaceous or much developed, and consist of a rather long stout 
stem, generally indistinctly quadrifid, and bearing in all twelve to sixteen points. The 
smaller branchize are simpler and the smallest rudimentary. The genital orifices lie 
below and between the third and fourth plumes on the right; the vent (which is not 
much higher up) below and between the fourth and fifth. 
The frontal veil is 8 mm. wide, thick, and not very ample. It bears sixteen small 
rounded tubercles, which give it an indented appearance. It is not distinctly bilobed, 
but there is a space in the middle where the tubercles are absent or obscure, so that it 
falls into two halves. No trace of a tentacular groove could be seen. Above the frontal 
veil the head forms a raised transverse ridge, terminating in the rhinophore openings, 
which point right and left and not vertically. The rims hardly project at all, but on 
the lower side a small process extends downwards. The club of the rhinophores is 
short and conical; it is surrounded by about ten simply pinnate plumes. The tips 
are protruded, and there are slight indications of a tentacle-like appendage on the 
upper ends. 
The general colour of the intestines is yellowish. The central nervous system is 
as usual: the pleurocerebral ganglia pear-shaped, with signs of a division into two 
parts ; the pedal round. No eyes were found. The jaws are yellow, narrow, elongated 
and convex. They are 7 mm. long, not counting the curve, and, as they lie folded, the 
