of Edinburgh, Session 1879 - 80 . 
467 
Test moderately thick and solid, transparent. Vascular trunks 
enter near the centre of the left side, are of large size and branch 
freely ; none visible on the centre of the right side. 
Mantle thin. 
Branchial sac longitudinally plicated, showing externally a 
division into pouches. Meshes nearly square, the transverse extent 
being slightly the longer ; each contains six to eight stigmata. In 
the centre of each mesh a vertical oblique vessel connects the inter- 
papillar membrane at the top of the mesh with the transverse vessel 
at the bottom. Papillae at the corners long and conical, no inter- 
mediate ones. 
Dorsal lamina ribbed transversely, edge plain. 
Tentacles simple, 30 to 35, long and short alternately. 
Olfactory tubercle greatly elongated laterally, disposed in a series 
of irregular folds. 
Three specimens from Kerguelen Island, 28 fathoms. In one 
specimen the vascular ramifications in the test are more conspicuous 
than in the other two. 
Ascidia tenera, n. sp. 
External appearance. — Shape oblong, flattened laterally; posterior 
end rounded, anterior end rather blunt ; attached by the posterior 
third of the left side. Branchial aperture terminal, directed some- 
what ventrally, sessile, lobes well marked. Atrial aperture placed to 
the right of the dorsal border, about one-third of the way down, 
sessile, lobes well marked. Surface soft and somewhat velvety, 
marked with slight creases, mostly longitudinal ; near the apertures, 
especially the branchial, raised into minute pointed projections. 
Colour light brownish grey or pale horn-colour. Length, 5 cm. ; 
breadth, 3 cm. 
Test thin, soft, easily torn, transparent. Vessels moderately 
developed, trunks enter on the left side near the base. 
Mantle very thin, muscular bands delicate, course of alimentary 
canal visible from both sides. 
Branchial sac not plicated. Generally five or seven smaller 
transverse vessels between a pair of larger ones. Longitudinal 
internal bars narrow but well marked, bearing papillae at the 
VOL. X. 3 L 
