OF NORTHUMBERLAND AND DURHAM. 107 



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. — J. A. 



Professor E. Forbes thinks this species may be a variety of 

 Ascidia scabra, Miill., but the latter has the apertures terminal 

 and rather prominent, the inner tunic of a uniform red, and the 

 outer tunic closely covered with small granules ; characters 

 which do not agree with our animal. The opake white spot 

 between the apertures appears to be permanent, and a good 

 distinctive character in this species. 



** Depressed, and attached through their whole length. 



6. A. DEPRESSA, Aid. and Hanc. 



Body oblong ovate, very much depressed, pale green ; attach ■ 

 ed laterally through its entire extent by a distinct expansion 

 or disc, surrounding the whole. Apertures distant : the branch- 

 ial 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, form- 

 ing 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, £ 1, 2), but differs in the position of 

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

 near together at the anterior end, while in ours they are widely 

 separated. 



7. A. ELLiPTiCA, Aid. and Hanc. 



Body elliptical, a little convex on the upper side, and flat 

 beneath, of a dull and sub-opake brownish or yellowish white; 



