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"Mycale acerata, sp. n.
Sponge large, massive, with numerous small rounded mammillæ; surface finely reticulate and finely hispid. Colour creamy white in spirit. Consistence soft, the tissues being easily torn. The flesh reddish (but soon decolorized), and showing the glistening white strands of the skeleton.
Oscules in form of wide, thin-walled, cylindrical chimneys with rather jagged upper edges, about 1 cm. in height and 1-2 cm. in diameter.
Skeleton.—Ectosomal: a network of triangular meshes formed by bundles of oxeas, the strands being about •35 mm. thick and the meshes about •5 mm. across. Main skeleton formed of long thick anastomosing fibres, which attenuate gradually from 1.5 mm. in thickness and break up a little below the surface into panicles of much finer fibres, which support the dermal membrane and penetrate the strands and nodes of the dermal reticulum, giving rise to a finely hispid condition of the surface. Parallel groups of oxeas scattered in the choanosome.
Spicules.—Megascleres: oxeas, 850 x 16•25 µ, slightly curved, rather abruptly pointed at one end and more tapering at the other. These oxeas form the fibres and also are gathered into bundles, one spicule in length, of parallel oxeas, scattered in the choanosome.
Microscleres: large anisochelæ palmatæ, 105 x 50 µ, separate or in rosettes, usually with an angular bend in the shaft; with a triangular upper tooth 60 µ long, about the same length as the upper aloe, which latter are very wide. With the lower tooth oblong, 12.8 high, with a slightly convex edge; in one of the specimens this edge is produced into a denticle.
A smaller kind of anisochelæ palmatæ, 47 µ long and 17 µ broad, at the upper end, with a long oval tooth 20 µ long extending below the alæ.
Trichodragmata, 62 x 12 µ, the trichites being very fine, sharply pointed oxeas.
There are three fine specimens of this species, the largest forming a thick flabellate body 17 cm. high, 11 cm. broad, and 7 cm. thick.
The mammillæ are on an average about .75 cm. in height, and 1 cm. in diameter at the base. The new species bears a very close resemblance to Mycale magellanica, Ridley, which likewise has a mammillated, finely reticulate surface and glistening skeletal fibres, but here the surface is smooth and not hispid, and the megascleres are styles, or subtyles, such as are normally found in the genus Mycale. The microscleres also are different in the two species.
A second species of Mycale with oxeate megascleres is Mycale intermedia (O. Sch.), from East Greenland, noticed by Thiele. The Arctic specimen consisted only of a fragment; but the spicules, which are all considerably smaller than in the Antarctic species, have the following dimensions:—Oxeas 450 µ long, 10-12 µ. thick; large anisocheles 50-60 µ. long; small anisocheles 18 µ long.
Locality. Winter Quarters, 25-178 fath."