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Proceedings of the Royal Society 
corners of the meshes, and smaller more conical intermediate ones. 
Stigmata elongated, three or four in each mesh. 
Dorsal lamina rather broad, delicately ribbed transversely ; edge 
pectinated, having a small intermediate tooth between each pair of 
larger ones. 
Tentacles filiform, 40 in number, long and short alternately. 
Three specimens: one in good condition from Station 311 (West 
end of Strait of Magellan), 245 fathoms ; and two, one of them 
damaged, from Station 320 (off the coast of Buenos Ayres), 600 
fathoms. The two latter are slightly smaller than the dimensions 
given above. 
This species somewhat resembles Ascidia virginea , but is un- 
doubtedly distinct from it. That species differs from the present one 
chiefly in its greater length, its (slightly) greater number of tentacles, 
the absence of intermediate papillae, and in the condition of the 
dorsal lamina — all good characters. 
Ascidia pyriformis, n. sp. 
External appearance. — Irregularly pear-shaped, anterior end 
narrow, posterior broad and rounded. Attached by a small area 
near the posterior end of the left side. Branchial aperture terminal, 
placed on a long somewhat conical projection turned dorsally. 
Sides of this projection channelled by eight grooves leading down 
from between the lobes of the aperture. A strong elevated ridge 
extending from the base of the projection along the anterior part of 
the dorsal edge. Atrial aperture sessile, placed at the posterior 
extremity of this ridge, being more than half-way from the anterior 
to the posterior end. Surface irregular, prolonged into a few thickish 
processes for attachment at the base, slightly rough, the globular 
posterior end encrusted with sand and shell fragments. Colour dull 
dirty grey. Length, 5 cm . ; breadth, 3 cm. 
Test remarkably thin, except on the tubes and the ridge connect- 
ing them, the latter being very thick. 
Mantle moderately muscular over the branchial sac and on 
the tubes, membranous elsewhere. Tubes long, the branchial 
measuring 1*2 cm. and the atrial 8 cm. The former has a sharp 
bend dorsally and to the right above its middle, and at this point a 
