TUNICATA OF THE &.M.B.C. DISTRICT. 123 
between Port Erin and the Calf, depth twenty fathoms, 
on May 20th, 1888. Each specimen had a large Amphipod 
(Leucothoe spimcarpa, Abildg.) in the branchial sac. 
Roule* in 1884 proposed that the large and well-known 
genus Ascidia (= Phallusia, Savigny) should be broken 
up into three smaller genera which he named Ascidiella, 
Ascidia and Phallusia. He took as the type of the last 
Cuvier’s Ascidia mamillata, characterized by having the 
branchial sac reduplicated at its posterior end; while he 
separated the two former groups by two chief features, viz: 
(1) the anterior position of the nerve ganglion close to the 
dorsal tubercle in Ascidiella, and (2) the absence of a dorsal 
lamina posterior to the cesophageal aperture in the same 
genus. 
I believe that these are to a certain extent natural 
groups, and I have decided to adopt them here; but I must 
point out that while Phallusia is quite distinct, Ascidia 
and Ascidiella are not so easily distinguished as Roule 
supposes, and his definitions will have to be slightly 
altered if they are to have a more extended application 
than to the Ascidians of the coast of Provence. For 
example the present species, which I now place as an 
Ascidiella, while it has the ganglion placed close to the 
dorsal tubercle, possesses at the same time a well developed 
prolongation of the dorsal lamina behind the cesophageal 
aperture, and would consequently not find a place in any 
one of the three genera as defined by Roule.! I propose, 
then, to modify Roule’s generic characters by leaving the 
condition of the dorsal lamina out of consideration, and to 
be guided in arranging the species by the position of the 
nerve ganglion alone. 
* “Recherches sur les Ascidies simples des cotes de Provence,” Ann. du 
Musée de Marseille, Zoologie, t. ii., mem. i. 
t Loc. cit., and Recueil Zoologique Suisse, t. iii., no, 2, p. 214, 1886, 
