KKI'oltT ON Till: TUNICATA. 73 



20, 1876; lat. 52' 20' S., long. G8° 0' W. ; depth, 55 fathoms; bottom temperature, 

 8 0- 8 C. ; sandy bottom. 



Molgula gregaria, Lesson (sp.) (PI. IV. figs. 5-8). 



Cynfhia gregaria, Lesson, Centurie Zoologique, p. 157, pL 52, fig. 3. Paris, 1830. 



Gynthia gregaria, E. 0. Cunningham, Notes on the Reptiles, &c, obtaimil .luring the voyage of 



H.M.S. "Nassau," Trans. Linn. Soc, vol. xxvii. p. 488. 

 Molgula gregaria, Herdman, Preliminary Report, Proc. Roy. Soc. Etlin., 1880-81, p. 234. 



External Appearance. — The body is almost spherical or sometimes ovate, and is slight I v 

 compressed laterally. The posterior end is large and rounded ; the anterior is somewhat 

 narrower and slightly projecting. The dorsal and ventral edges are strongly and equally 

 convex. It is attached by the posterior end of the left side. 



The apertures are both at the anterior end, and are not distant ; the branchial is low, 

 hemispherical, and six-lobed ; the atrial is more prominent, narrower, and four-lobed. 

 The surface is smooth and glistening, slightly undulating and furrowed, and occasionally 

 a little wrinkled. The colour is white, with usually a hyaline blue tinge. 



Length of the body, 7 cm. ; breadth of the body, 8 cm. 



The Ted is cartilaginous and solid ; it is moderately thick and strong, and almost 

 opaque ; no vessels are visible. 



The Mantle is thick, but not very muscular. 



The Branchial Sac is strong, with seven distinct but narrow folds on each side. 

 The internal longitudinal bars are strong but few. The transverse vessels are very 

 irregular; they divide and anastomose to form a network in the meshes of which the 

 irregular and complicated infundibula are set. The stigmata are rather small, and they are 

 curved and arranged in spirals. Broad horizontal membranes attached to the internal 

 longitudinal bars run alone; the chief transverse vessels. 



The Dorsal Lamina is rather thin, but broad ; it is crumpled, but neither ribbed nor 

 toothed. 



The Tentacles are large and much branched; they are fourteen in number, and of 

 two sizes, placed large and small alternately. 



The Dorsal Tubercle is elliptical or kidney-shaped ; both horns are much coiled, and 

 form large spirals ; the aperture is at the right side. 



This species, like the last, was first described as a Cynthia. As no account of it has ever 

 been published except as to the external appearance, I have given here a full description 

 and figures. 



The specimens differ somewhat in appearance on account of the condition of the 

 test. This seems to vary considerably, being in some individuals thin, except at the 

 posterior end, while in others it is much thicker, staffer, and more opaque (as in the 

 specimen figured, PI. IV. fig. 5). The lobes around the prominent apertures are very 

 distinct, and the branchial has, in addition to the six ordinary lobes, a series of six much 



