112 BRITISH TUXICATA. 



The mantle (PI. VII, figs. 7 and 8) is thin and deli- 

 cate, with the muscular fibres fine and for the most part 

 transverse and diagonal. 



The branchial sac (PL XVII, fig. 11) extends the 

 whole length of the body, and is minutely plicated, 

 and the secondary vessels are rectilinear, with the 

 extremities of the vessels obtuse ; the primary vessels 

 are pretty equal in size, and the longitudinal bars 

 somewhat more numerous than the plications. The 

 papillae are alternately large and small; with rounded 

 extremities, and the membrane in connexion with the 

 larger ones or those at the intersections is moderately 

 developed. The oral lamina (PI. XIX, fig. 8), which is 

 rather wide, is ribbed on the right side, and the smooth 

 or left side has a row of minute papillae just within 

 the free margin, extending from one end to the other ; 

 sometimes the papillae are double. The tentacular 

 points on the left side of the mouth are rather large. 

 The tubercle in front of the lamina is horse-shoe 

 formed, with the limbs turned forwards. The tenta- 

 cular filaments are very numerous, long, and much 

 crowded ; they are arranged in a broadish belt, having 

 the smaller in front, the larger behind, so that there 

 seem to be two or three rows of them. 



The ovary appears on both sides of the intestinal 

 loop, but is most extensively developed on the left 

 side, where it assumes the form of a complicated en- 

 tanglement of small and contorted branches. The 

 cells covering the stomach are large. 



15. Ascidia elongata Alder & Hancock. 

 (PI. XVII, fig. 12.) 



[A*c i di a I'lonyata, ALDER & HANCOCK in Ann. Xat. Hist. (4) 

 VI (1870), p. 360.] 



Hilij elongated, slender, transparent, nearly colour- 

 less, attached slightly at the side of the base ; the 

 bnnn-li.inl aperture terminal, the <n/<if about two-thirds 

 down. Test hyaline, minutely tuberculated, the tuber- 



