of Edinburgh, Session 1880-81. 
69 
slightly by the posterior end of the left side. Apertures sessile, 
inconspicuous ; branchial terminal and median ; atrial on the dorsal 
edge, one-fourth of the way down. Surface even, but partially 
covered by a thin coating of sand. Colour dirty grey. Length, 
1 cm. ; breadth, *8 cm. 
Test cartilaginous, thick but soft. 
Mantle very thin, closely united to the test. 
Branchial sac wide, with four folds on each side. The alternate 
transverse vessels wider than the intermediate ones. Internal 
longitudinal bars stout, six on each fold, and only one in the inter- 
space. Meshes transversely elongated, containing each about six 
stigmata. 
Dorsal lamina narrow, margin plain. 
Tentacles simple, numerous, long and short alternately. 
One specimen from Port Jackson, 2 to 10 fathoms. 
Styela convexa , n. sp. 
External appearance. — Shape rudely hemispherical or bluntly 
conical, not flattened ; anterior end and sides convex, posterior end 
large, attached to a stone and slightly expanded at the edge. 
Branchial aperture terminal, rather to the ventral side of the 
middle of the anterior end, but forming its most prominent point ; 
atrial aperture moderately distant, at the dorsal edge of the anterior 
end; both are sessile and inconspicuous. Surface moderately smooth, 
finely creased in all directions, especially round the apertures. 
Colour dull yellowish-brown, lighter on the margins of the posterior 
end. Length, 2 cm. ; breadth (dorso-ventral), 2*6 cm. 
Test thin but very tough, white on section. 
Mantle closely united to the test, musculature fine but close. 
Branchial sac with four folds on each side. About eight internal 
longitudinal bars on a fold, and the same number in the interspace. 
Meshes elongated vertically, containing each about three stigmata, 
and divided by a narrow horizontal membrane. 
Dorsal lamina slightly crimped but plain, edge even. 
Tentacles simple, stout, rather curled, about thirty in number, 
and all of much the same length. 
VOL. xi. 
K 
