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Show 1881.] THE SURVEY OF H.M.S. 'ALERT.' 133 increased by Carter (Ann. & Mag. Nat. Hist. ser. 4, xx. pp. 38, to include the Arctic region, is now extended southwards and into the Pacific. Hab. Tom Bay (S. W. Chili), 0-30 fathoms ; on dead Retepora. CLATHRINA POTERIUM, Hiickel. Ascetta primordialis, var. poterium, Hiickel, Kalkschwamme, ii. p. 17, pi. v. fig, \,f-i. Found in the form of a running tube {Auloplegma form), as in («) of the preceding species; diameter of tube "25 to '53 millim.; slightly pigmented with diffused red-brown pigment, concentrated into a granular mass in some places (possibly due to a siliceous or a horny sponge which grew in the neighbourhood). The triradiate spicules are of two sizes, as shown by Hiickel for his Australian variety poterium ; but they are connected by intermediate stages. The large dermal form (which is occasionally bluntly pointed) varies in the diameter of its rays from -019 to -02217 millim.; one ray is usually about 7 : 6 of the length of the other two, being from "13937 to "1774 millim. long, while the smaller rays are '1267 to '1584 in length. The smaller, subdermal spicules have rays measuring about •118 and '1267 (respectively, in the one spicule) by '095 to '01056 millim. The largest of the larger triradiates only form a single surface layer; the smaller subjacent forms are much more numerous. The extreme diameter of the rays of the larger spicules is thus considerably less than the average diameter given by Hiickel for the Australian form, viz. '025 millim.; and the smaller spicule-rays are considerably shorter in proportion to their length than in that form. Hab. Tom Bay (S.W. Chili), 0-30 fathoms; on an Ldmonea on which a horny sponge was growing. Obs. I have followed Hiickel's suggestion (p. 23, torn, cit.), and advanced this form to the rank of a species, being justified, as I consider, in this course by the fact that it is constant to its main characters as described from the Australian specimens, even at the great distance from which it is now recorded. It is distinguished from d. primordialis, Hiickel, by the minimum diameter of its largest spicule-ravs exceeding -02 millim., and by the possession of a special dermal set of triradiate spicules considerably larger than those subjacent to them. NARDOA PELAGICA, sp. n. (Plate XI. fig. 4.) {Nardoa, Schmidt, Adr. Spong. p. 18 ; Ascandra, Hiickel, Kalkschwamme, ii. p. 80.) Sponge forming a flattened cylinder, of about equal diameter from the mouth to the base, which is almost flat. Length 19 millims. • long and short diameters respectively 7 and 3 millims. Wall 1 millim thick. Lip? Skeleton consisting of scattered stout acerates piercino-' the wall from the dermal to the cloacal surface, of an external laver of triradiates whose longest ray either points inwards or towards the base, of a less number of similar spicules imme- |