OCR Text |
Show 132 ZOOLOGICAL COLLECTIONS MADE DURING [Jail. 4, With regard to the amount of distinctness between the new species and their nearest allies, the remarks or tables given under each sponge should be consulted. It should be remembered, in estimating the relations of this fauua, that comparatively few species have been intelligibly described from any seas but the Atlantic and Mediterranean ; but "even allowing for that, the fact that in but one case the nearest ally is to be found outside those two areas speaks strongly for the Atlantic fades of the Magellan and S.W. Chilian fauna. Subclass CALCAREA. The technical terms here used are those employed by Hiickel in his 'Kalkschwamme,' and with the meanings there applied to them. The collection, it will be seen, contains the British form Clathrina coriacea (hitherto known only from arctic and north temperate seas) and the Australian species C. poterium as its sole representatives of a Magellan fauna. Considering the number of dredgings in shallow waters which have been taken here, this result may be considered as probably showing the extreme poverty of this region in Calcisponges. A striking contrast to this is furnished by the dredgings at the Victoria Bank, a shoal to the north-east of Rio de Janeiro, which was not visited by the ' Challenger,' and from which no Sponges have hitherto been described. Of the four (or possibly five) species which come from this locality, three are new, and a fourth has been assigned with considerable doubt to one of the species obtained. The well-known littoral habits of the Calcarea are thus brought forcibly to mind; for had they been fitted to live in deeper waters, it is almost inconceivable that more of them would not have spread from the mainland, whose fauna is already somewhat known. CLATHRINA CORIACEA, Johnston. {Clathrina, Gray, P. Z. S. 1867, p. 557; Ascetta, Hiickel, Kalkschwamme, ii. p. 14.) Spongia coriacea, Montagu?, Wern. Mem. ii. p. 116. Grantia coriacea, Johnston, Brit. Spong. p. 183, pi. xxi. fig. 9. This species occurs ou a few species of dead Retepora, forming either (a) a minute tube {Auloplegma form of Hiickel) running over the surface, expauding at intervals into a bulbiform dilatation, and varying in diameter from "18 to "426 millim., or (6) apparently a thin-walled sac of not less than 2'5 millims. extreme diameter. The sarcode is coloured reddish brown by an unevenly distributed pigment. The spicules agree with the common type figured by Hiickel in the 'Kalkschwamme,' pi. v. fig. 2, differing slightly from it in being sharply though abruptly pointed, and in being slightly inequiradiate ; they measure:-in (a), basal ray -1267 to '14 millim., laterals -095 to "114 millim. long, diameter "00844 to "0095; in (b), basal ray -114 to "2027, laterals "114 long, diameter "00844 to "0095 millim. These measurements agree closely with those of the spicules of Johnston's specimens of Grantia coriacea. The distribution, already |