Mr. J. Alder on the British Tunicata. 155 



a little the broader ; the test is very much thinner, and attached 

 obliquely at the base; the apertures are more distinctly grooved 

 and less distant; and the branchial sac has not the intermediate 

 papillae, nor is it reflected upwards as in A. mentula. It appears 

 to be a northern species. 



The longitudinal strands of the branchial meshes in this 

 species are very tender, and are often found broken in spirit 

 specimens, and contracted towards the papillae, giving the latter 

 the appearance of being tricuspidate. 



Ascidia rudis, n. sp. 



Body oblong or ovate, rather irregular, depressed, greenish, 

 attached largely by the side. Apertures distant, the branchial 

 terminal, the anal generally about halfway down : ocelli red, 

 reniform. Test thick, coriaceous, coarse, wrinkled, and very 

 slightly tuberculated, sometimes nearly smooth. Mantle bluish- 

 green, with a yellowish tinge towards the upper part; the aper- 

 tures distinctly tubular; the anal tube often much extended, 

 and entering into a sheath in the substance of the test. Tenta- 

 cular filaments few and slender. Branchial sac green, with stout 

 papillae at the intersections of the meshes, and frequently with 

 intermediate ones on the longitudinal strands : ventral plait 

 transversely ribbed. Length about 2^ inches. 



Several specimens were obtained by Mr. Norman, at low- 

 water mark, near the Whalsey Lighthouse, Outer Skerries, Shet- 

 land, in company with a large variety of A. depressa, to which 

 externally it bears some resemblance; but it has a much closer 

 affinity with A. mentula, and has probably hitherto been taken 

 for a variety of that species. There are, however, sufficient 

 grounds to consider it distinct. A. rudis never reaches the size 

 of A. mentula, and is of a different colour ; it is much more 

 largely attached, and bears small, distant tubercles. The tubular 

 form of the anal orifice in the mantle, too, is characteristic, 

 though this is not conspicuous outside, the tube being imbedded 

 in the thickening of the test, and the external aperture varying 

 in position in proportion to its length. In a variety from 

 Hastings, which I owe to the kindness of Mrs. Blackett, the 

 tube is very much elongated within the test, and opens at a very 

 short distance from the branchial aperture. Usually, however, 

 it is situated about halfway down, pretty near to the position it 

 occupies in the mantle. 



Ascidia plebeia, n. sp. 



Body oblong, slightly scabrous, attached for nearly its whole 

 length, greenish. Branchial aperture terminal, produced, conical; 

 anal aperture about two-thirds down, slightly raised : ocelli small, 



