OCR Text |
Show 1881.] THE SURVEY OF H.M.S. 'ALERT.' 119 of that genus are settled, it will be well to adhere to the more comprehensive term Esperia for these forms. The nearest allies of this Sponge, of which intelligible descriptions or specimens are available, appear to be :- Spinulate spicule. J^orate. Acetates. Esperia nodosa, Schmidt, "1 '4117 by -011085 -0577 m m . -057 m m . Adr. Meer. Suppl. i. p. 33 J mm. (Adriatic). E. bowerbanki, id. Adr. 1 About same as -06334 m m . Ditto. Meer. p. 55 (Adriatic)... J preceding. EMatatf. ibid.(Adri- j .g9Q fey .Qm ^ .05384 m m .Qm mm< E. rhopalophora and E. intermedia, Schmidt, from the North Atlantic, may perhaps prove, when more fully described, to come near this species. Rhaphidotheca affinis, Carter, from off the north of Scotland, differs but slightly from it in the forms of its spicules ; but their sizes are greater. For details of appearance in life see Dr. Cunningham's work on the Straits of Magellan above mentioned. ALEBION PROXIMUM, sp. n. (Plate X. fig. 8.) Incrusting. Surface covered with numerous narrow convolutions, and minutely roughened; vents scattered, '2 to '3 millim. in diameter. Colour dark brown. Main skeleton composed of primary columns of spiculo-fibre running from base towards surface ; fibres 5 to 6 spicules thick, crossed by secondary bars approximately at right angles, bars 2 to 5 spicules thick. Dermal skeleton a regular polygonal network of spiculo-fibre, 1 to 5 spicules thick, beneath which lie irregular tracts of cylindrical spicules. Spicules united in fibres by a minimum of sarcode. Parenchyma very granular, reddish brown. Skeleton-spicules of two kinds:-(i) acuate, covered from base to apex with short spines, tapering from within about 5 diameters of apex to a sharp point, size "15835 by "0095 millim., in main and dermal skeleton ; (ii) cylindrical, tapering from middle to a neck, terminated by a distinctly spined head, at each end, size -15835 by "0079 millim., in subdermal tracts. Flesh-spicules of two kinds:-(i) inequi-anchorate, upper palm conical in outline, inferior edges angulated, shaft slender, lower palm small, triangular, terminated by a sharp point, length '02534 millim., scattered; (ii.) bipociilate, exactly similar to that of the British species Halichondria hyndmani, Bowerbank, size '01056 millim. broad (from back of shaft to front of the curves), scattered. Examined. In spirit and by mounting in balsam. External Characters. This species is represented by a specimen coatino- one valve of a Pecten. It resembles Halichondria hyndmani and other nearly allied British forms in its corrugated surface. At the centre of the shell it is merely a brown film. The convolutions are sometimes substellately arranged, and may be as much as |