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 T. pallida 

 Stimpson (Cape of Good Hope), T. incerta Bergh (New Zealand), T. appendiculata Eliot 

 (South Orkneys), T. (Candielld) australis (South Chile). The animal described as 

 Microlophus poirieri, by MM. A. T. Kochebrune and J. Mabille in the " Mission 

 Scientifique du Cape Horn," 1882-3, Vol. VI., p. 11-12 and plate 6, la and lb., is 

 probably a Tritonia. 



1. TRITONIA CHALLENGERIANA (juv. ?). 

 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 

 branchiae 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 branchiae 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 



