REPORT ON THE TUNICATA. 211 



The tentacles are filiform and are few in number ; they are of two .sizes, placed larger 

 and smaller alternately, and situated rather far apart. 



Ascidia nigra seems to be a common and widely distributed species. Lesueur's 

 specimens were from St. Vincent and (iuadaloupe, Hay of Calicoua ; and Traustedt's from 

 St. Croix, and St. Thomas; those obtained during the "Argo" expedition were from 

 Antigua and Tucacas ; and there are some specimens in the British Museum collection 

 from the Eed Sea. The Challenger specimen from Bermuda is rather small, measuring 

 about 6 cm. in its greatest length (antero-posterior), and 4 cm. in breadth. Those probably 

 from Station 142 are larger, being about 10 cm. in length. 



One specimen of this species is from Bermuda, shallow water, and three probably from 

 Station 142, December 18, 1873; lat. 35° 4' S., long. 18° 37' E. ; depth, 150 fathoms; 

 bottom temperature, 8°"3 C. ; bottom, sand. 



Ascidia falciger -a, Herdman (PL XXXII. figs. l-f>). 



Ascidia faleigera, Herdman, Prelim. Rep., Proc. Roy. Soc. Edin., 1879-80, p. 469. 



External Appearance.- — The body is elliptical or nearly round in shape, and is usually 

 depressed. The area of attachment is large, including pari of the ventral edge and the 

 entire posterior end, and extending sometimes half-way up the left side. The edge of the 

 base is often expanded into a thin spreading margin. The apertures are on the upper 

 (right) side, near the anterior end, and not far apart ; the branchial is terminal or subter- 

 minal, the atrial is about two-fifths of the way down, and at a short distance from the 

 dorsal edge. The branchial is almost sessile, while the atrial is slightly prominent ; the 

 lobes are very distinct, especially those around the atrial aperture. 



The surface is smooth and soft, but slightly wrinkled. The colour varies from a light 

 grey to a pale horn tint ; it is darker at the apertures. 



The length and breadth are variable ; as an average may be taken — length of the 

 body, 5 cm. ; breadth of the body, 4 cm. 



Tlie Test is thin all over, except at the base of attachment, w r here it is greatly thickened, 

 and has small stones, &c, imbedded in it. Large vascular trunks are visible in this 

 thickened base, elsewhere the vessels are few and of small size. 



The Mantle is moderately muscular, especially on the siphons and down the centre of 

 the right side. 



The Branchial Sac extends to the base of the mantle, and is not longitudinally 

 plicated. The transverse vessels are all narrow. The internal longitudinal bars are 

 moderately strong, and bear long tapering papillae, which are curved like tusks, at the 

 anoles of the meshes ; there are no intermediate ones ; the horizontal membranes are 

 very broad, and form large flat vesicles occupying the concave sides of the papilla!. The 

 meshes are square, and each contains three to five regularly arranged stigmata. 



The Endostyle is well marked, and of a yellow colour ; it ends abruptly at the base of 

 the ventral edge of the sac. 



(ZOOL. CHALL. EXP. — PART XVII. — 1882.) R 28 



