OF THE SCOTTISH NATIONAL ANTARCTIC EXPEDITION. 531 
stems is bifurcate, more rarely trifurcate, and each of these secondary (neti ends in 
three (sometimes only two) small blunt points. 
Down the middle of the back runs a low distinct ridge, sending off side ridges to 
the large branchiz but not to the small ones. There are two branchiz on each side 
before the first of these ridges. There are four of the transverse ridges in the anterior 
part of the body, but in the posterior portion both the longitudinal and transverse 
ridges become obliterated. 
The veil (fig. 16) is ample, not bilobed, 9 mm. wide and projecting 2°5 from the head 
without the processes. It bears at each end a grooved tentacle of the shape usual in 
Tritonia, and twelve to fourteen digitate appendages, large and small, alternating with 
fair but not absolute regularity. The larger measure 2 mm., the smaller are about 
half the size. 
The rhinophore sheaths are rather low (2 mm.), fairly wide, with a wavy margin. 
| 6 
3 5 
Zz 
2 18 19 4 20 (4) 
I7 
Fic. 17.—Central tooth, Fic. 18.—Central tooth, Fics. 19, 20.—Lateral teeth. 4 is nearergthe rhachis 
from the side. from above. than 5 and 6. 
Fics. 17 to 20.—Tritoniopsis brucei. 
In front they carry two or three appendages, each bearing three points, and suggesting 
that a branchia is fused with the sheath. The club of the rhinophore is smooth and is 
surrounded by about twelve appendages, many of which are quite simple, while others 
bear a few pinne. 
The orifices are not at all conspicuous. In the specimen in which they can be seen 
best the genital orifices lie below and between the fifth and sixth plumes, and the anus 
between the seventh and eighth, rather sigue up but some distance from the dorsal 
margin. 
The central nervous system resembles Bereu’s figure of this organ in Atthila 
ingolfiana (Nud. Gasteropoda of the Ingolf. Exp., pl. v. fig. 12). The four ganglia 
are all of much the same size and round. They are mottled and apparently granulate. 
The cerebro-pleural ganglia are not pear-shaped or larger than the pedal, and show no 
signs of a division into two halves. The buccal ganglia are rather large. No eyes are 
visible. 
The jaws are yellowish, fairly hard and strong, rounded, not elongate, very convex. 
TRANS. ROY. SOC. EDIN., VOL. XLI. PART III. (NO. 22.) 79 
