SPONGIIDA. 405 



has a slightly but regularly uneven surface, the tissue covering it 

 being, however, almost smooth. Vents with thin everted margins 

 about -5 millim. high, abundant, irregularly uniserial, 1 to 3 millim. 

 in diameter on one (presumably the upper) side of the stem and 

 branches, less abundant and generally smaller on the opposite side. 

 Branching dichotomous, at angles of 60° to 60° ; the branches rather 

 flexuous ; branches and stem 8 to 18 millim. in diameter. Texture 

 in spirit firm, but flexible, tough ; colour dark dull grey. Main 

 skeleton composed of tough, flexible primary fibres of closely packed 

 spicules, about 6- to 12-serial, running approximately at right 

 angles to surface (no horny uniting^-matter visible), the fibres 

 nearly approximated to each other ; and of irregular and often loose 

 crossing secondary tracts of spicules 2 to 4 spicules broad, not strictly 

 at right angles to primaries. Dermal skeleton a closely-set coat of 

 subparaUel spiculo-fibres about 8 spicules broad. Barcode dark 

 brownish, granular. Spicules acerate, slightly but sharply bent, 

 tapering slightly from middle, and rather suddenly from within 

 about two diameters of ends, to moderately sharp points ; size -2 by 

 •0128 miUim. 



Hah. Port Darwin, 7-12 fms. ; bottom mud and sand. 



Distribution. East-Indian seas (Esp&r) ? 



The only specimen measures 150 millim. (6 inches) in extreme 

 length. The species is at any rate distinct from Spongia arboreseens 

 of Lamarck, who gives ;Si. lobata, Esper, as a synonym of his species. 

 It stands on the borderland between PachychaUna and the branched 

 and large-vented Eenieridse. I assign it to the former, as its fibres 

 are evidently formed in part by a flexible horny material. It difi'ers 

 from the described specimens of S. lobata in having approximately 

 cylindrical branches and bearing some vents on both sides. 



36. Pachychalina macrodactyla. (Plate XL. figs. B, B'; 

 Plate XLI. fig. o.) 



Spongia macrodactyla, Lamarck, Ann. Mws. Hist. Nat. ^x. p. 467. 



Guided only by the short and superficial description given by 

 Lamarck, and by the locality (" probably Indian Ocean ") assigned 

 by him, I refer to his species some dry fragments of an exquisite 

 Pachychalina, possibly originally belonging to one specimen. It 

 Las some external resemblance to Spongia asparagvbs, Lamarck, of 

 which. I have seen a specimen ; but the branches in the latter are 

 cylindrical, the vents open on the level of the general surface, 

 and the fibre-structure is that of Ohalina rather than Pachychalina. 

 I will proceed to supplement the original incomplete description by 

 a fuller one. 



The stem and branches are flattened out, somewhat knife-like, in 

 most places, the edges being sometimes quite sharp ; the lateral 

 diameter is here about twice the antero-posterior one (viz. about 18 

 miUim. at largest part of stem, 9 miUim. just below apex of branches) ; 

 the stem near the base appears to be normally cylindrical, about 6 

 millim. in diameter. Branches (in present specimens) given off pin- 



