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Show 1900.] MARINE F A U N A OF CHRISTMAS ISLAND. 137 swellings along the body, one of the ends attenuated sometimes to a blunt point. Amphidiscs 18 p. The characteristic feature of the new variety lies in the strongyles with their peculiar swellings ; these may, however, be dependent on some pathological cause such as the presence of a parasite, but I was unable to find any such organism. Tin several descriptions of this species the dermal diactines are described as tylotes. In the type specimen from Port Darwin the ends of the strongles are very slightly enlarged, a feature slightly exaggerated by the artist in the figures (11. p. 435, pi. xiii. fi'g./); but there is no trace of terminal enlargement in the spicules of specimens from the Mascarenes, Madras, and. Cliristmas Island.] DESMACELLA sp. A few small broken-up pieces of a very soft dark reddish-brown incrusting sponge, with a few crater-like oscules. The skeleton forms a unispicular network, the meshes of which are triangular and quadrangular and made up of styles, oxea, and strongyles. A few long slender toxa and one or two sigmata, together with some slender raphides, are present. The skeleton is renieroid, and spongin entirely absent. The dimensions of the spicules are :- Styles (not rare) slightly curved, 150 x9ju; strongyles (rare) straight, 126 x6 p. Oxea (very abundant), curved, 180 x 7 p. Microscleres-toxa 48 x -5 p (rare); sigmata 24 p (very rare); raphides (rare), 108 x 1'5 p. This species, which appears to be new, has not been named owing to the uncertainty as to whether all the above-mentioned microscleres seen in the preparations really belong to the sponge ; several kinds of obviously foreign spicules were included. STYLOTELLA IRREGULARIS, sp. n. (Plate XII. fig. 4; Plate XIII. figs. 6 a-d.) Sponge incrusting or forming free irregular lamellae; colour pale brown ; with several small circular oscules 2 to 3 m m . in diameter on the upper surface. Skeleton forming a rectangular network, the meshes being for the most part unispiculate, but with a few slender primary lines of spiculo-fibre 2-4 spicules thick. Spicules. Styles 186 x9ju, smooth, straight or slightly curved. Oxea 204 x 9 p, curved. Strongyla 150 x 10 p, straight or slightly curved. Slender oxea 150 x Ap, occasionally with a central fusiform enlargement, rare and scattered in the tissues. This species is very near Petrosia contignata Thiele, from ebes (Zoologica, Stuttgart, 1899, Heft 24, ii. p. 20), but differs mainly in possessing slender fusiform oxea; unfortunately the central swelling is not shown in PI. XIII. fig. 6 d. STYLOTELLA sp. Specimen incrusting, 2 x 1 c.c. in area, and -25 to *5 c.c. in thickness ; pale brown, very soft, with several oscules 1 m m . in diameter. |
