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Show 1881.] THE SURVEY OF H.M.S. ' ALERT. 125 Hab. Trinidad Channel, near Madre-de-Dios Islands, off S.W. Patagonia, 30 fathoms. Obs. The two already described species, Halichondria aspera and Isodictya rudis, Bowerbank, both from the Straits of Malacca, possibly merely varieties of one species, together with Tedania suc-toria, Schmidt, from Iceland, resemble our species in important points. It is also noteworthy that Schmidt refers (Spong. atl. Geb. p. 43) to a shapeless white specimen of a Tedania from Bio de Janeiro, to which he gives no name. Looking at the locality and at this description, one would not be surprised to find that it proved to be our species. The two Malacca species have a most interesting relation to the rest; for with the terminally microspined heads of the cylindrical spicule, characteristic of the Mediterranean Tedanice, they combine a very marked roughening of the fine acerate-an irregularity of the surface which is only possible to make out, in the case of T. tenuicapitata, with very good light, and then not always, and which is, so far as I am aware, peculiar to the acerates of this genus, being wholly distinct from spination or " microspination." Tedania suctoria, Schmidt, has cylindrical with two smooth heads, as in our species; but they are not terminally pointed as here. It is probably the most nearly allied of described species. Its spicule-characters. for comparison with those of T. tenuicapitata, are:- T. suctoria. (Iceland.) | tapering very gradually Smooth Acuate Spicule. \ from head. Size -5325 [ by -01583 m m . Heads oval, rounded Cylindrical Bicapitate.. - Fine Acerate Skeleton • i off terminally. Size "3357 to "38 by 008445 m m . Surface-roughness generally perceptible. Size •2924 by "00285 m m . ( Main-skeleton fibres more compact. Dermal cylin-dricals radiate more regularly ; bundles larger and less distinct than in the other species. T. tenuicapitata. (S.W. Chili.) Beginning to taper about 6 diam. from end. Size •38 by -01267 m m . Heads slightly oval, pointed. Size -2787 by -006334 m m . Surface-roughftess rarely perceptible with certainty. Size -316 by •002114 m m . Skeleton-fibres as loose as possible. Dermal cylindrical in distinct bundles, radiating each from a separate point. A M O R P H I N A sp. inc. A minute, thin, incrusting patch on the worm-tube which bore Alebionproximum. It is white; and the sarcode is granular, but almost colourless ; the spicules are smooth, sharply bent acerates, ending rather abruptly in points, and resembling those of A. genetrix, Schmidt, but far smaller, and massed in flattened tracts. Hab. Sandy Point, 7-10 fathoms. |