366 Mr. H. J. Carter's Contributions to our 



From the above observations, then, it follows that a sub- 

 division of the Tethyina might stand thus : 



Section 1. 



Without zone-spicule or ungirled. (Azosta.) 



a. Sessile forms. (Sessilia.) 



b. Rooted forms. (Radicifera.) 



Section 2. 



With zone-spicule. (Zosterophora.) 



a. Sessile forms. (Sessilia.) 



b. Rooted forms. (Radicifera.) 



The Geodina, Stellettina, and Tethyina are often globular 

 in general form ; but this appears to arise from their base of 

 attachment having been destroyed, probably at a very early 

 period of their development, when they adapt themselves to 

 their environment, and thus, having no fixed point, become 

 round. 



New Species. 



Tethya merguiensis 1 Crtr. 



(PL XV. fig. 6, a-j\ fig. 7, a-k y and fig. 8, a-h.) 



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

 base (fig. 6, a-f). Consistence loose, soft. Colour black- 

 brown. Surface uniformly hispid from the protrusion of 

 spicules, interrupted only by several large vents of different 

 sizes, chiefly situated towards the circumference (fig. 6, b). 

 Pores in the interstices of a fibro-dermal reticulation whose 

 sarcode, charged with dark brown pigmental cells and flesh- 

 spicules, is thus rendered strikingly cribriform (fig. 8 y a-h). 

 Internal structure radiating in large bundles from the centre, 

 which is midway between the base and the summit (fig. 6, c 1 d), 

 separating as they advance towards the surface and leaving 

 wide intervals between them, which form a cavernous kind of 

 excretory canal-system that opens at the vents mentioned. 

 Spiculation comprising six forms, viz. : — 1, body-spicule (which 

 is by far the largest), acerate, attenuatingly sharp-pointed, 

 fusiform, smooth, nearly straight, about l-6th by l-600th inch 

 in its greatest dimensions (fig. 6, a and e) ; 2, zone-spicule, 

 smooth, trifid, arms radiating laterally and a little forwards at 

 equal angles from each other and from the shaft, which is so 

 like them in size and shape that, when 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 of this kind ; 



