Report on the zoological collections made in the Indo-Pacific Ocean ...

;SPONGHDA. 623longer and has more bends than the stout form, which could thusonly have been derived from it by fission or retrogressive absorption,methods unknown, so far as I am aware, in the normal developmentof siliceous sponge-spicules.46. Spirastrella transitoria. (Plate LIV. figs, q, q'.)Sessile, incrusting. Surface broken up by slight intercrossingridges into very shallow angular areas 1 to 2 millim. wide ; surfacebetween and over ridges subglabrous. Consistence in spirit tough,elastic ; colour pale pinkish brown.Main skeleton chiefly composed of dense fascicles of the skcletonspicule,with the points radiating outwards, set at various angles tothe surface, viz. from right angles to a horizontal jiosition ; thepoints of the bundles frequently project slightly beyond the surface.Sarcode dense ; that of surface subtransparent, dark greenish yellowof subjacent tissues very pale yellow, transparent.Spicules:— (1) Skeleton spinulate, straight or nearly so; headspherical, neck distinct ; head and centre of shaft of about the samediameter, viz. '016 millim. ; shaft tapering to sharp point from about7 diameters from apex ; length of spicule about '9 millim. (2) Spinispirular,extremely conceutrated, composed of only one entire bend ;spines numerous, closely aggregated, strong and sharp ; shaft about•004 millim. thick ; spines "004 millim. long; length of spicule,includiug spines, -OIG millim.Hub. Darros Island, Amirante group, 22 fms. ; bottom brokencoral.This species is represented by a specimen of about 1 square inchin superficial extent, covering and following the iu equalities of asmall mass of shells and Polyzoa ; the thickness varies from about•5 to 2 millim. It appears to be most nearly related to the formtermed by Mr. Carter (Ann. & Mag. N. H. 1882, ix. p. 352)" Spirastrella cunctatrix, variety," from Mauritius ; but this form isstated to be white, to have a spinispirular with tivo bends, of a lengthof about "036 millim. It differs from S. cunctatrix, Schmidt, in theshorter spinispirular, and the globular, not oval, head of the spinulate.In S. transitoria we have the spinispirular almost in the form of thestellate, with which Schmidt (Spong. Atl. Geb. p. 5) and Carter(op. cit. 1879, iii. p. 355) consider it to be homologous.47. Spirastrella punctulata. (Plate LIV. figs. p,p'.)" Suberites P sp. undesciibed, Mauritius," Carter, Ann. iSf Mag. N. H.1882, ix. p. 352.Elongated, subconical. Vents single or few, terminal, oval, about2 millim. in greatest diameter. Surface obscurely nodose, andcovered besides on the upper parts of the sponge with a minute, butclose and regular pitting, giving the appearance of shagreen ;pitsand intermediate elevations low, each about -3 millim. in diameter