156 Mr. J. Alder on the British Tunicata. 



red. Test thin, transparent, roughish with small papilla?, and 

 slightly covered with fragments of shell and sand, especially to- 

 wards the attached part. Mantle yellowish green. Tentacular 

 filaments numerous and stout. Branchial sac with papilla? at 

 the intersections of the meshes, and occasional small inter- 

 mediate ones on the longitudinal strands : ventral plait plicated. 

 Length about two inches. 



Examples of this species were dredged on the Outer Haaf, 

 Shetland, by the Rev. A. M. Norman and J. Gwyn Jeffreys, Esq. 

 I have also met with one or two Ascidia from the coasts of 

 Northumberland and Durham, which I am inclined to refer to 

 the same. It has affinities with A. aculeata and A. depressa. 

 From the first it may be known by its more elongated form, its 

 more prominent apertures, and by the papilla? of the test being 

 smaller, fewer, and not echinated ; from the latter by its thinner 

 test and less area of attachment, as well as by the absence of the 

 thickened margin or disk that divides the upper from the under 

 surface in that species ; from both it may be distinguished by 

 the fragments of shells with which it is more or less covered. 



Ascidia aculeata, n. sp. 



Body ovate, depressed, greenish, more or less attached by the 

 side to sea-weeds or zoophytes. Apertures nearly sessile, acu- 

 leated, the branchial terminal, the anal about one-third down 

 the side. Test thin, transparent, greenish or nearly colourless, 

 covered with aculeated tubercles most prominent on the upper 

 or left side. Mantle greenish, transparent, showing the reticu- 

 lations of the branchial sac and sigmoid intestine. Tentacular 

 filaments small. Branchial sac with moderate-sized papilla? at 

 the intersections ; the stomata elliptical : ventral plait smooth. 

 Length an inch to an inch and a half. 



I first met with this species, many years ago, in Torbay. It 

 has since been found at Bantry Bay and Guernsey, by Mr. Nor- 

 man, and by Dr. W. B. Carpenter in Lamlash Bay, Arran. It is 

 usually attached to sea-weeds, and appears to inhabit shallow 

 water. 



This species comes nearest to A. depressa, but is less depressed, 

 less largely attached, and without the marginal disk dividing the 

 upper from the under surface ; the test is more uniformly thin, 

 and has stronger and more sharply pointed tubercles. The 

 apertures are also less distant. The tubercles are frequently 

 compound, bearing several aculeations. This is probably the 

 "Ascidia mammillaris, Delle Chiaje" of Thompson's 'Natural 

 History of Ireland/ but, I think, not of Delle Chiaje, judging 

 from his figure. 



