ON THE ACEPHALA. 373 



A. ALBiDA, Alder and Hancock, 



" Body ovate, wliite, transparent, and slightly tuberculated. 

 Attached laterally by a narrow base to small sea-weeds. Branchial 

 aperture lateral or subterminal, large but not very prominent, the 

 margin divided into eight points with intermediate red ocelli. 

 Anal aperture a little distant from the other, and nearly half 

 way down the body, on the upper side ; largish, and little 

 prominent, with six red ocelli. Outer tunic hyaline and colour- 

 less, covered with distant small tubercles. Inner tunic trans- 

 parent white with bluish lines on the upper part ; below, opaque 

 white slightly spotted with yellow. There is a large opaque 

 white spot on the ganglionic prominence between the apertures, 

 near which are a few small reddish marks. Length, half an inch ; 

 breadth, one-third less. On small sea-weeds brought in by the 

 trawl-boats, with the last. Not uncommon." — Ald. Cat. p. 107. 



A. DEPREssA, Alder and Hancock. 



" Body oblong ovate, very much depressed, pale green ; attached 

 laterally through its entire extent by a distinct expansion or disc, 

 surrounding the whole. Apertures distant ; the branchial one 

 terminal, not much produced, and divided into eight points, with 

 intermediate red ocelli ; anal aperture about two-thirds down the 

 body on the left side, with six segments and intermediate ocelli. 

 Outer tunic transparent, granulated or tuberculated on the upper 

 surface, the granules sometimes a little incrusted with brown ; 

 under or attached side smooth and very thin. Inner tunic one- 

 third less than the outer, yellowish green, of a deeper colour and 

 sometimes inclining to orange in the lower part. The intestine 

 is often very conspicuous, forming a dark sigmoid coil, but this is 

 more or less the case in all the transparent species. Branchial 

 sac finely reticulated, with tubercles at the intersections. Length 

 nearly an inch. Common ; attached to the underside of stones, 

 among the rocks at Cullercoats and Whitley. 



" This species comes very near to the Ascidia orbicularis of 

 Miiller (Zool. Dan. t. 79, p. 1, 2), but differs in the position of 

 the apertures, which in that species are represented to be rather 



