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“Tethya antarctica, n. sp. Pl. XX.
Body globular; colour tawny yellow. Surface smooth, interrupted frequently by through which the spicules of the interior project in bundles, cactus-like (Pl. XX. figs. 1 & 2). Dermal sarcode cribriform, from the number of minute "pores" in it (fig. 4), with here and there a large circular vent (fig. 2, c c c). Summit presenting three or more large vents, which branch off internally into the excretory canal-system (3, a a a). Base furnished with tufts of long spicules, anchor-and fork-headed respectively, some of which have their heads in the sponge and their shafts free, and vice versâ (fig. 2, e). Internally cavernous, arising from a much dilated state of the excretory canal-system, whose extremities are peripheral, where the sponge-structure appears to be densest. Spicules of three kinds, viz.:--- acerate, very slightly curved, and long‑pointed (fig.5); 2, anchor-headed, of two forms, viz. one with thick arms, hastiform (fig. 7), the other with the arms more expanded (fig. 8); 3, tri-for-headed, one prong much longer than either of the other two, which are equal (fig. 6). No bihamates. The first or acerate spicule is chiefly confined to the body, and the two other kinds to the surface, being longest most numerous at the base. Thus the spicules generally vary much in length. The largest acerate form averages 1-20th of an inch in the adult sponge (fig. 9); and the longest fragment of shaft found with anchor-head attached did not exceed 1 ¼ inch (fig. 10). Generally the longest of thse spicules do not appear to have been more than 1 ½ inch in length. The hastate form of anchor-head appears to be chiefly confined to the body, and the expanded or grapnel form to the free extremities of the spicules of the tufts at the base of the sponge. Size of young Tethya antarctica figured 1-16th of an inch in diameter exclusive of the tufts at the base—inclusive of the tufts, 5-48ths, or about 1-10th of an inch long (fig. 1). Size of largest fragment of adult spong 4 inches long.
Hab. Marine; deep sea, in 206 to 300 fathoms.
Loc. Antarctic Ocean, in lat. 74 ½° and 77 ½ °S., and long. 175°W
Obs. I have little to add tot what has already been stated of this sponge. The description of the form is taken from that of the young one found in the parents, and the details of structure from the adult fragments; so that the whole is almost as complete as if we had had the adult entire. Generally the sponge corresponds to the Tethydæ of which T. cranium is the type, modified more or less by the great dilation of the excretory canal-system, in which it more particularly agrees with Carteria and Holtenia. It is also tufted at the base for fixature in the mud and sand; but in this it does not resemble the sponges any more than Tethya dactyloidea, which not only is similarly tufted at the base, but presents a large vent at the summit, through chich the excretory system of canals empties itself (Annals, 1869, vol. iii. p. 17, and 1872, vol. ix. p. 82). Perhaps most of all it is like Schmidt's Tetilla polyura, which came from Desterro, on the coast of Brazil; but it contains no bihamates, which makes it differ, I think, from all the other species known but the one from Shetland, about to be described.
I am not able to state if, like the other Tethyadæ, its internal structure radiated from a nucleus; but if so, the fragments would lead me to infer that this must have been situated towards the base. Here, of course, our young one does not assist us, as to ascertain this point by its destruction would not compensate our loss of the only entire form of this sponge that we possess.
With reference to the nature of the grains of sand which pervade these fragments, I might here state that they have a lava-like aspect and structure, as if they originally came from the active volcanoes witnessed and measured by Sir James Ross on the adjoining continent.”