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Show 120 ZOOLOGICAL C O L L E C T I O N S M A D E D U R I N G [Jan. 4, 2 millims. in height. Pores 1 Vents distant from each other by 2 to 7 diameters. Texture fragile. Skeleton appears somewhat confused in transverse sections ; but this is partly due to the opacity of the sarcode, which conceals in part the relations of the fibres. Spicules aggregated loosely in fibres. The colour of the parenchyma resembles that of most Microcionce and most of the British Halichondria (Bowerbank) which are related to this species. Skelelon-spicules. The heads of the cylindrical are well marked, being nearly as broad as the maximum diameter of the shaft; their external halves are covered with small but distinct spines. The whole spicule presents an exaggerated form of the corresponding type in H.pattersoni, H. hyndmani, and H. ingalli (in which species its head is faintly microspined). Flesh-spicules. The inequiancho-rate is of the same form, down to the inferior spine of the small palm, as in the above-named species, as is the bipocillate ("bipo-ciliated anchorate" of Bowerbank, "grotesque spicule" of Carter). The latter, which was very seldom found in the microscopic mountings, is decidedly larger than in any of the British allied species. For further relations to these forms, see table of comparison {infra) with the type specimens of Bowerbank's species. Hab. Sandy Point, 7-10 fathoms (on a Pecten). Spicules-Characters and Proportions. Alebion proxvmvm (Straits of Magellan). A. (Halichondria) pattersoni, Bowk. (Britain). A. (H.) hyndmani, Bowk. (Britain). A. {H.)ingalli,'Bawk. (Britain). Spined Acuate. Slightly spined all over; tapering from near apex; •15835 by -0095 m m . Slightly spined all over; tapering from near middle; "23436 by -010537. Spines mostly near base; tapering from middle; -228 by •0095. Spines mostly near base; tapering from middle; '152 by •006334. Cylindrical. \ I •> anchorate. With distinct heads; •15835 by -0079 mm. Heads scarcely distinguishable from shaft; -247 by •006334. Very slight, faintly spined heads;49630 by -038. Heads less visible and less spined than in preceding; 4457 by 02534. As in British species. •025337mm. long. •025337 long. •02275 long. •01583 long. Bipocillate. As in British species. •01056 mm. broad. About -008 mm. broad. •008445 mm. broad. •008445 mm. broad. Alebion, Gray (P. Z. S. 1867, p. 534) seems to be the only genus at all correctly defined, of the four in which he has placed these and the allied species ; the character of " branching " should, however, be omitted from it. Probably Myxilla rubiginosa, Sdt., from the Adriatic, is allied to these forms; but Schmidt does not mention any minute flesh-spicules from it. |