TITNICATA OF THE SCOTTISH NATIONAL ANTARCTIC EXPEDITION. 91 



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 Cliallenger Report is not very 

 difierent 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 Scotia in consider- 

 able quantity at the South Orkneys. It was originally described by SLUITER * from two 

 specimens obtained by the French Antarctic Expedition under Dr JEAN CHARCOT at " He 

 Booth Waudel, 40 metres " ; 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. Miis. Hist. Xat. Paris, 1905, No. 6, p. 472 ; and Expe'd. Antarct. Fraiif. (Charcot), " Tuniciers," p. 40. 



(BOY. soc. EDIN. TRANS., VOL. XLVIII., 309.) 



