80 



MR. H. J. CARTER ON A COLLECTION OF 



to have been produced by the bleaching action of the strong 

 alcohol in which the specimens were preserved. 



Tethta merguiensis, n. sp. (Arm. & Mag. Nat. Hist 1883, 

 xi. p. 366, pi. xv. figs. 6 a-f, 7 a-Jc, 8 a-h.) 



Circular, convex, sessile, depressed, rather constricted at the 

 base (I.e. fig. 6, Consistence loose, soft. Colour black-brown. 

 Surface hispid, interrupted by several large vents of different sizes, 

 chiefly situated towards the circumference (I.e. fig. 6, b). Pores 

 in the interstices of a dermal spicular reticulation whose sarcode, 

 charged with dark-brown pigmeut-cells, is thus rendered cribri- 

 form (I.e. fig. 8, a-h). Internal structure as in T. robusta, viz. 

 the spicules radiating in bundles from the centre, which lies, as 

 in that species, midway between the base and the summit 

 (I. c. fig. 6, d). The spicules diverge as they advance towards 

 the surface and leave wide intervals between them, forming a 

 cavernous kind of excretory canal-system which opens at the 

 vents. Spiculation comprising five or six forms, viz. : — 1, the body- 

 spicule (which is by far the largest), acerate, nearly straight, 

 fusiform, smooth, gradually sharp-pointed, nearly by l-600th 

 inch in its greatest dimensions (/. c. fig. 7, a) ; 2, zone-spicule, 

 smooth, trifid, arms straight, diverging laterally and a little for- 

 wards, placed at equal angles from each other and from the shaft, 

 which is so like them iu size and shape that, when not in situ, it 

 is not only almost impossible to say which is which, but whether 

 the spicule is or is not a gigantic 4-rayed stellate, arm about 

 l-56th inch long, sometimes one or more are abnormally bifid 

 (I. c. fig. 7, bb); 3 and 4, anchors and forks, heads as usual, but 

 filiform from the great length of their whip-like, delicate shafts 

 (I. c. fig. 7, c. d) ; 5 and 6, flesh-spicules, viz. the usual form of 

 bihamate, 1\ 6000ths inch long (/. c. fig. 7,f, h), and a thin, fine 

 acerate about l-100th inch long (I. c. fig. 7, g). No. 1, together 

 u irh nos. 3 and 4, projecting in great abundance far beyond the 

 surface, from their extreme length give the hispid character 

 which characterizes the sponge. Pigmental cells, which are 

 abundantly scattered throughout the sarcode generally, and from 

 whose brown granules the dart colour is derived, about l^-GOOOth 

 inch in diameter. Size of specimen about 10-12ths inch in its 

 greatest horizontal diameter (which is between the base and the 

 summit), G-12th8 inch high. 



