14 WwW. A. HERDMAN. 
emphasise the difference in the number of folds in the branchial sac, as that would 
prevent the present species from being placed with M. chrystallina in a genus Pera, 
characterised by having five branchial folds on each side. 
MoLGULA LONGICAULIS. 
(Plate V., figs. 1 B, 3 and 8-11.) 
Locality.—Winter Quarters, in McMurdo Bay. One specimen measuring 4 em. in 
total length, including the stalk, which is 3 mm. in diameter, body 2°7 em. in length 
x 1 em. in breadth. ; 
External Appearance.—Body long and narrow, tapering posteriorly to a long 
narrow peduncle, the lower recumbent half of which (fig. 3) is attached to a 
specimen of Molgula concomitans (fig. 1). The anterior end is bent over ventrally 
in such a manner that the six-lobed branchial aperture appears to be placed one- 
third of the way down the ventral edge, and the four-lobed atrial aperture projects 
terminally ; both apertures are on short siphons. The surface is smooth and glistening 
all over, but somewhat wrinkled as the result of contraction. Colour grey. 
Test thin and membranous, smooth both inside and out, transparent. 
Mantle rather thin, but with a moderate musculature rather like that of an Ascidia, 
the muscle bands being distinct and yellow, though rather distant, and forming an 
irregular network, with fusiform swellings at intervals (fig. 9). 
Branchial Sac with seven folds on each side. The internal longitudinal bars are 
narrow and rather distant, about six on a fold and two or three in the interspace. 
Stigmata very irregular, so as to break up the transverse vessels and render them 
inconspicuous (fig. 10). 
Dorsal Lamina a short plain membrane. 
Tentacles could not be determined with certainty on account of their condition. 
Dorsal Tubercle large, of distorted cordate form (fig. 11), with both horns rolled 
inwards. 
Alimentary Canal placed at posterior end and along dorsal edge of left side 
(fig. 8). Intestine long and narrow, forming a circular loop, after which the rectum 
adheres closely to the stomach and cesophagus. An unusually large curved renal sac 
occupies the right side. 
The single specimen of this new species, which I name longicaulis, because of the 
elongated stalk which it possesses—a very unusual character in a Molgula—is 
unfortunately not in good condition. The outside appearance and proportions are 
probably very much as in life, but the branchial sac and tentacles, which seem delicate, 
are to some extent disorganised, so that it is difficult to determine the internal 
characters with certainty. Fig. 10 is made up of fragments visible here and there in 
several preparations of the branchial sac. The condition of the transverse vessels and 
of the tentacles must be left an open question. 
