THE " TRITON " TUNICATA. 99 



attachment. The colour is dirt}' grey. Length, 5 cm. ; greatest breadth, 

 2 cm. ; thickness of peduncle, 1 cm. 



The test is thin, except at the top of the peduncle, where it is considerably 

 thickened. The peduncle is solid, and formed of test alone. The vascular 

 trunks enter the test at the top of the peduncle. 



When the test is removed the body has the appearance usual in Ascidia 

 virginea, and the mantle is in a normal condition, strongly muscular on the 

 right side, but thin and weak upon the left. 



The branchial sac corresponds in all respects with what I have found in 

 other specimens of the species. It is longitudinally plicated to a slight degree, 

 has strong internal longitudinal bars with no papillae, and square meshes with 

 five or six stigmata each. 



The dorsal lamina is strongly ribbed transversely. The tentacles are 

 numerous, closely packed together, and of several sizes. Those of the first 

 order are long and slender. The dorsal tubercle is simple, and elongated 

 antero-posteriorly. The posterior three-fourths or so is enclosed in the small 

 peritubercular area, and the end is pointed. The aperture is anterior, and 

 the horns are not coiled (PI. XVII. fig. 4). Ascidia virginea is one of the 

 most variable species known, in regard to the shape of the dorsal tubercle. 4 ' 5 ' 

 The present form is rather simpler and more symmetrical than usual, and is 

 peculiar in having the posterior end pointed. 



The single specimen was trawled off the Butt of Lewis, 25th August 1882, 

 depth, 40 fathoms. 



Ciona intestinalis, Linn. (PL XVII. figs. 1 and 2). 



Sixteen specimens of this common British species were in the collection sent 

 to me, four of them being preserved in absolute alcohol. They were all obtained 

 by the trawl at Station 3 (8th August 1882, at the north-west end of the 

 Wyville-Thomson ridge, and north of the " warm area," bottom s. sh.) from 

 a depth of 87 fathoms. This is the greatest depth known to me at which this 

 species has been found, but it is quite possible that it may have been obtained 

 in Scandinavian seas, or in the Mediterranean at greater depths, though I have 

 been unable to find records of such instances. The " Triton " specimens are 

 all of fair size, and as some of them are much corrugated it is probable that 

 they were large individuals when alive and expanded. 



The tests are more colourless than is usual with shallow water specimens 

 from our own coasts, and have almost none of that dull green tint which may 

 generally be observed even after preservation in spirit. On the other hand, 



* See Herdman, "On the 'Olfactory Tubercle' as a Specific Character in Simple Ascidians," 

 Proc. Roy. Pliys. Soc. Edin., vol. vi. session ex. p. 256, 1881. 



