14 W. 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 cm. in 

 total length, including the stalk, which is 3 mm. in diameter, body 2'7 cm. in length 

 x 1 cm. 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. l). 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 oesophagus. 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. 



