DE. W. A. HERDMAN ON BRITISH TUNICATA. 285 



tral ; left side flat, right slightly convex. Attached by posterior 

 end of left side towards ventral edge ; the area of attachment 

 forms a well-marked base, almost a short stalk, with the posterior 

 margin slightly expanded. Both apertures on right side, sessile ; 

 branchial almost terminal ; atrial about one fourth of the way 

 down, near the dorsal edge. Surface smooth. Colour light yel- 

 lowish grey. Length 6 centims., breadth 3 centims. 



Test thin, but tough ; vascular trunks enter in the lower third 

 of the left side (at the anterior end of the base), and radiate over 

 that side, where they are conspicuous. 



Mantle rather thin; muscle-bands fine, but numerous. 



Branchial sac delicate, not longitudinally plicated ; the alter- 

 nate transverse vessels are stronger than the intermediate ones ; 

 in some places, however, the latter are wanting. The internal 

 longitudinal bars bear large curved papilla?, those at the intersec- 

 tions with the slighter transverse vessels, or where these ought to 

 be, smaller than the others. Meshes slightly longer transversely 

 than vertically ; stigmata short and regular, six to eight in a 

 mesh, 



Dorsal lamina closely ribbed transversely; margin toothed, 

 rather irregularly. 



Tentacles very numerous, packed closely together, of at least 

 three sizes, the smallest being very minute. 



Olfactory tubercle simply ovate in outline, the opening anterior* 



Locality. Upper end of Loch Long, 5 fathoms. 



For this and a few of the other specimens I am indebted to 

 my friend Mr. D. .Noel Paton, B.Sc, to whom this species is 

 dedicated. 



Ascidia MURICATA, Heller. (Plate XVIII. figs. 1, 2.) 



Ascidia muricata, Heller, Untersuchungen u. d. Tun. d. Adriat. u. Mit- 

 telm. 1 Abth. p. 13, Taf. iv. figs. 6-7 &Taf. v. fig. 1 (1874). 



This species, which was found by Heller at Lesina, I dredged 

 twice in Lamlash Bay last September. The specimens were small, 

 being only half the size of those from the Mediterranean, but 

 agree well with the description and figures. Heller gives a full 

 account of the external appearance ; but for the internal charac- 

 ters merely says that the form of the branchial sac, the papilla?, 

 and the dorsal fold are like those of Ascidia mentula. I therefore 

 add the following details taken from the Scottish specimens. 



'Branchial sac not longitudinally plicated, or very slightly so ; 



