﻿I^b •ENDEAVOITE" SCIENTIFIC RESULTS. 



give the name digitata is probably identical with the typical 

 variety, but in the absence of sufficiently full information con- 

 cerning the latter, I do not feel justified, on mere assumption, 

 in naming it as such. 



Crei.i.a ixcrust.ws, Carter, var. digitata, 77ir. nov. 



(Plate xxiii., fig. j, and figs. 28, _>9.) 



Sponge, so far as fe/;on.'H, gru-iuing upoti the sliells of 

 bivalve molluscs in the form of a thick encrusting layer 

 from ivhich arise shorter lobes or longer digitations. 

 Texture loose; consistency soft, though moderately 

 tough. Oscula? Fibres si)iuous, injastomosing, cored 

 solely by smooth oxea, and plentifidly, though by no 

 means densely echinated. The der^nal skeleton comprises 

 oxea in addition to acanthostyles ; the latter spicules do 

 not form a definite reticulation. Megascleres, nnnximum 

 sizes: — {i.) Oxea 220 x 4.^ \i ; {ii.) principal acanthostyles 

 I'jo X 9 ;/; {Hi.) dermal acanthostyles go x 8 ;<. Isochelce 

 arctiatcB ij to 20.5 ^ long. 



This variety is represented by six specimens which were 

 obtained by the "Endeavour" from a single locality. Each 

 of them grows upon the shell of a Pecten, forming a thick 

 cushion-like layer which spreads over the entire exterior sur- 

 face of both valves, the two portions being in continuity only 

 across the hinge-line. Though the shells are now empty, it is 

 evident that the animals must have remained alive until the 

 sponge grew to considerable proportions. At the free margin 

 of the valves further growth is effected by the formation of 

 processes which vary in form from short thick blunt lobes to 

 elongated branch-like digitations (Plate xxiii., fig. 2). Similar 

 processes may also arise from other parts of the surface. The 

 condition presented lin some specimens indicates that the 

 sponge may attain to a considerable size without any forma- 

 tion of outgrowths ; in others, the total mass of the branches 

 may exceed that of the encrusting portion. Anastomoses of 

 the branch-like processes occasionally occur. The surface may 

 be glabrous and even, or may exhibit minute conuli at the 

 points where the fibres impinge. The oscula, which in the 

 typical variety have been described by Carter as large and 

 scattered, are not with certainty discernible in the present 

 specimens : the dermal membrane is, however, ruptured in 

 places, and thus, on account of its elastic tension, rounded 

 openings result, which might easily be mistaken for oscula. 

 The non-appearance of oscula in the present instance is 

 possibly due to their closure whilst the sponges were being- 

 dragged in the trawl-net. The dermal membrane is thin, yet 



