OF NORTHUMBERLAND AND DURHAM. 201 
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.—/. A. 
Professor H. 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. pEprEssa, Ald. and Hane. 
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, f. 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. exurptica, Ald. and Hane. 
Body elliptical, a little convex on the upper side, and flat 
beneath, of a dull and sub-opake brownish or yellowish white ; 
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