REPORT ON THE TUNICATA. 157 



Tlie Tentacles are filiform ; there are about thirty very long thin ones, with inter- 

 mediate shorter ones. 



The Dorsal Tubercle is large, and is transversely elliptical in shape ; both horns are 

 rolled inwards, and form large spiral cods. 



This is an attractive-looking species, with its nearly rectangular form and milk-white 

 soft looking test. From some points of view it looks like a little white barrel. The aper- 

 l ures are at the extremities of the anterior end, and are distinctly cross-slit (PI. XIX. 

 fig. 7). 



The test is not at all like that of a typical Styela, it is thick, soft and flexible. The 

 mantle is muscular but thin, and is closely attached to the test. 



The internal longitudinal bars are wide ribbon-like bands, but they are few and dis- 

 tantly placed. Consequently the meshes are greatly elongated transversely, containing 

 usually about fifteen stigmata each (PL XIX. fig. 8), but in some cases (e.g., the most 

 ventrally placed meshes) as many as forty. The transverse vessels are alternately 

 larger and smaller (tr. and tr.% while here and there the smaller ones fail, and a row of 

 very long stigmata is formed. Delicate horizontal membranes are present, here and there, 

 between the transverse vessels, dividing parts of the meshes, but they never extend far 

 (PL XIX. fig. 8). 



Three specimens of this species were obtained at Kerguelen Island, at depths of from 

 10 to 100 fathoms. 



Styela exigua, Herdman (PL XIX. figs. 5 and 6). 



Styela exigua, Herdman, Pielira. Rep., Proc. Roy. Soc. Edin., 1880-81, p. 68. 



External Appearance. — The body is quadrangular in shape ; it is a little longer than 

 broad, and is somewhat compressed laterally. The anterior end is broad and rather flat, 

 while the posterior end is narrower and more rounded. The body is attached slightly 

 by the posterior end of the left side. The apertures are sessile and inconspicuous ; 

 the branchial is terminal and median, the atrial is on the dorsal edge, one-fourth of 

 the way down. 



The surface is even, but partially covered by a thin coating of sand. The colour is a 



dirty grey. 



Length of the body, 1 cm.; breadth of the body, 0"8 cm. 



Tlie Test is cartilaginous and thick, but soft. 



Tlie Mantle is very thin, and is closely united to the test. 



The Branchial Sac is wide, with four folds on cadi side. The alternate transverse 

 vessels are wider than the intermediate ones. The internal longitudinal bars are stout ; 

 there are six on each fold, and only one in the interspaces. The meshes are transversely 

 elongated, and contain each about six stigmata. 



