238 
Proceedings of the Royal Society 
Dorsal lamina , a plain broad membrane. 
Tentacles branched, thin, about twelve large and twelve smaller, 
and three orders of simple and very minute ones placed alternately 
to the others. 
Olfactory tubercle having an elongated oval cavity, ending in a 
quadrangular aperture anteriorly. No horns. 
Four specimens from Kerguelen Island; 10 to 110 fathoms. 
Ascopera, n. gen. 
Body pyriform, more or less pedunculated ; attached. 
Test thin, between membranous and leathery. 
Branchial sac , with seven folds on each side. Stigmata straight 
or curved, but not arranged in spirals. 
Ascopera gigantea, n. sp. 
External appearance. — Shape roughly pyriform, not compressed 
laterally. Anterior end wide, truncated, slightly cleft in the centre, 
ending in a siphon at each extremity. Behind the siphons the body 
swells out into a globular form, and then becomes continuous with 
the wide stalk formed by the posterior two-fifths of the test. Dorsal 
edge rather more convex than ventral. Attached by the extremity 
of the posterior end. Apertures both at anterior end, distant, con- 
spicuous, wide ; branchial at the ventral edge, very large, funnel- 
shaped ; bent round so that the opening is directed posteriorly ; 
atrial at the dorsal edge, more anterior than branchial, wide, directed 
anteriorly. Surface even ; finely roughened all over. Colour pale 
yellowish grey-green. Length, 30 cm. ; breadth, 12 cm. 
Test thin and almost membranous, but tough ; semi-transparent ; 
smooth on inner surface. 
Mantle delicate and membranous, with a few distant, rather 
strong muscle bands running transversely over the anterior half or 
so of the right side and the left side ; only absent on the dorsal part 
of the left side and the posterior end. 
Branchial sac very thin and delicate, seven folds on each side ; 
those next the endostyle are rather slighter than the others. Internal 
longitudinal bars wide and delicate. These and the wide and distant 
transverse bars give off vessels which branch and anastomose, forming 
an irregular network, the spaces of which are the stigmata. 
