300 LIVERPOOL MARINE BIOLOGY COMMITTEE REPORT. 



Ascidia aspersa, 0. F. Miiller. 

 Ascidia aculeata, Alder, Ann. and Mag. N. H., v. xi, p. 156, 1803. 



Several small specimens of this common west coast 

 species were dredged off Port Erin during August. They are 

 decidedly smaller than the usual specimens from Lamlash 

 and Loch Fyne, and the outer surface of the test is not so 

 distinctly roughened. The tentacles, which are small, rather 

 distantly placed, and of three distinct sizes, and the dorsal 

 tubercle * are good, and, so far as my experience goes, fairly 

 constant characters by which the species may be determined. 

 In some of the specimens the internal longitudinal bars of 

 the branchial sac showed a good deal of variation, being 

 frequently incomplete or wanting for several meshes. This 

 was especially the case in the neighbourhood of the dorsal 

 lamina, and of the endostyle. 



Ascidia plebeia, Alder. (PI. VI, fig. 5.) 



Several specimens of this species were dredged from a 

 depth of twenty fathoms, off Spanish Head, Isle of Man. 

 It has not been previously recorded from the neighbourhood. 



The specimens show considerable variation in the external 

 appearance, one being quite smooth on the surface, nearly 

 transparent, and very much compressed laterally; it is 

 attached by the entire left side to the inner surface of a 

 Lamellibranch shell. Another specimen is only attached 

 slightly by the posterior end of the body, and has the test 

 rough and of a dull green colour ; various foreign particles 

 are attached. There is a good deal of variation also in the 

 position and length of the branchial and atrial siphons. 



In one of the Manx specimens, the dorsal lamina has 

 long projections from its free edge, opposite the transverse 

 vessels of the branchial sac. It looks much more like a 

 series of languets connected by a slight membrane, than like 



* For the shape see Herdman, Journ. Linn. Soc, vol. xv, pi. xvi, fig. 3. 



