TUNICATA OF THE SCOTTISH NATIONAL ANTARCTIC EXPEDITION. 309 
colour pale yellowish grey. The branchial aperture is a little way along the ventral 
edge of the anterior end, and appears to be bilabiate or elliptical rather than lobed. 
The atrial aperture is in the middle of the dorsal surface, and is a square or four-lobed 
opening. In F. cinereus, the branchial aperture was described as triangular, and the 
atrial as bilabiate, but the figure of the former in the Challenger Report is not very 
different from the figure now given (fig. 16) from the Scotia specimen. 
The Test is thin and membranous, but tough. Under the microscope it is seen to be 
finely roughened all over the outer surface. In minute structure the test agrees with 
that of F’. cinereus as described in the Challenger Report. The Mantle is very thin and 
inconspicuous, but muscular. It is penetrated by numerous, very fine, closely placed 
muscle bundles which, in the tubular extension of the mantle which occupies the hollow 
peduncle, run longitudinally parallel to one another. 
The Branchial Sac is remarkably delicate, and is, in fact, merely a very loose wide- 
meshed net with folds at intervals where the longitudinally-running vessels are crowded 
together (fig. 17). The transverse vessels are of two sizes, occurring alternately. The 
looseness of the branchial sac and the minute undulations in practically all the muscle 
bundles of the mantle give the impression that when alive and filled with sea-water the 
animal had the power of expanding to a considerably larger size than it now shows. 
Possibly the test when alive was of a gelatinous consistency and capable of being 
dilated. 
There are no spicules in the vessels of the branchial sac. The endostyle is narrow 
but conspicuous ; there are no spicules in its wall. The branchial tentacles are few and 
only slightly branched. The alimentary canal is relatively small, and is confined to 
the posterior end of the left side close to the top of the peduncle (fig. 18). The stomach 
wall has a number of close-set longitudinal folds. 
The gonads are one on each side, rather long and irregular, with the narrower end 
pointing to the atrial aperture (fig. 18). 
This new species differs from Fungulus cinereus, Herdman, in the shape and pro- 
portions of the body (see figures) and in the much paler colour of the test; in the 
details of position and shape of the branchial and atrial apertures; in having the trans- 
verse vessels of the branchial sac distinctly of two sizes; in having a well-marked 
stomach with longitudinal folds; and in the length and shape of the gonads. 
Halocynthia setosa, Sluiter. 
This very striking and characteristic species was obtained by the Scotea in consider- 
able quantity at the South Orkneys. It was originally described by Sturrer™* from two 
specimens obtained by the French Antarctic Expedition under Dr Jean Cuarcor at “ Ile 
Booth Wandel, 40 métres”; but as the figures in the report on the Charcot Expedition 
did not seem to me to be characteristic, I gave a supplementary description, with figures, 
* Bull. Mus. Hist. Nat. Paris, 1905, No. 6, p. 472 ; and Expéd. Antarct. Frang. (Charcot), “ Tuniciers,” p. 40, 
