REPORT ON THE TUNICATA. 71 



(8.) January 11, 187G ; Station 31L Straits of Magellan ; lat. 52° 45' 30" S., long. 

 73° 46' 0" AV. ; surf. temp. 50° ; two specimens of the aggregated form (4 cm. in length). 



(9.) February 14, 187G; Station 320, South Atlantic, off Buenos Ayres ; lat. 37° 

 17' 0" S., long. 53° 52' 0" W. ; surf temp. 67°"5 ; one specimen of the aggregated form, 

 and one specimen of the solitary form (6 cm. in length). 



(10.) March 9, 1876 ; Station 331, South Atlantic ; lat. 37° 47° 0" S., long. 30° 

 20' 0" "W. ; surf. temp. 64°-5 ; three specimens of the aggregated form. 



(11.) April 28, 1876; North Atlantic; lat. 17° 47' 0" N., long. 28° 28' 0" W. ; 

 surf temp. 73''"5 ; three specimens of the aggregated form (from 2 cm. to 2-5 cm. in 

 length, two of them imperfect). 



(12.) Collected during the cruise of H.M.S. "Knight-Errant;" North Atlantic, to 

 the north-west of Scotland ; several specimens of the aggregated form. 



Both the solitary and the aggregated forms in this collection differ somewhat from 

 the figures of the species given by Traustedt. 



The two specimens of the solitary form from Station 166 (see PL YII. fig. 4) have 

 the two laterally placed spines near the atrial aperture and the broad truncated anterior 

 end, and the muscle bands are wider than in the aggregated form, although not so 

 wide as in the specimens figured by Traustedt. The pointed posterior end is relatively 

 longer, and tapers to a finer point than is the case in Traustedt's figure. In all other 

 respects the specimens are typical. The two specimens collected in the Pacific, on 

 March 16, 1875, have the posterior processes all well marked and sharp pointed, and in 

 other respects agree with the typical form. 



The large specimen of the solitary form from Station 320 measures 6 cm. in length 

 and 2 cm. in breadth. It has very wide muscle bands, more like those figured by 

 Traustedt than any of the other Challenger forms. They are about 8 mm. in width. In 

 the shape of the body, however, this specimen is not in the typical condition. It has a 

 very short process at the posterior end of the body, which is not quite median in posi- 

 tion, and the lateral spines are very slightly developed and are unsymmetrical. In these 

 respects this specimen shows an approach to the characters of the aggregated form. 



The aggregated form of this species was met with by the Challenger much more 

 frequently than the solitary; and the specimens collected by the "Knight-Errant" 

 Expedition in the North Atlantic during the summer of 1880 belong entirely to the 

 aggregated form. These specimens differ in shape amongst themselves to a consider- 

 able degree (PL VII. figs. 1, 2, and 3). The anterior end may be rounded and blunt, 

 or conical and pointed, or quite irregular in shape ; while the posterior end may also 

 be irregularly rounded, or may be produced to form a process tapering more or less to 

 a point. This pointed posterior end is never median, but turns somewhat towards the 

 right side of the body in all the specimens (PL VII. figs. 2 and 3). The sides of the 



