400 Mr. II. J. Carter on 



from the detritus of the root-mass of Ewplectella cucumer, 

 which came from the Seychelles, in which it is very plentiful. 

 It is equally unusual, too, to find a scopuline spicule in a form 

 like that of Hexactinella ventilabrum. 



RacodiscuJa (Zittel) asteroides (Crtr.). 

 (PI. XIV. fig. 11, a-g.) 



Form massive, thick, short, cylindrical, excavated cup- 

 like, divided below into three or more root-iobes, which have 

 been cut off, thus reducing the height to 3^ in., with a maxi- 

 mum breadth horizontally of 2§ in. ; excavation conical 

 downwards, about 2| in. deep, commencing in a closed, round, 

 pointed end below, expanding upwards into an irregularly oval 

 aperture above, about If by 1 in. in its greatest dimensions ; 

 wall about f in. thick at the brim, increasing downwards as 

 the wall of the excavation recedes from the surface. Consis- 

 tence compact, heavy. Colour sponge-yellow-grey. Surface 

 even. Pores not seen. Vents numerous, chiefly opening 

 into the bottom of the excavation, also scanty and very large 

 here and there on the surface, unless the latter be worm-holes. 

 Spicules of four forms, viz. : 1, minute, elliptical, elongate, 

 subdiscoid, niicrospinecl, about 3 by l-6000ths in. in its 

 greatest dimensions (fig. 11, d, g) ; 2, minute acerate, curved, 

 fusiform, gradually sharp-pointed, thickly microspined all 

 over, about 11 by |-6000ths in. (fig. 11, c, f) ; 3, large 

 acerate, comparatively long, smooth, curved, fusiform, also 

 gradually sharp-pointed, 83 by f-1800ths in. in its greatest 

 dimensions (fig. 11, e) ; 4, tetractinellid spicules of the skele- 

 ton, which commence in a nail-like discoid form on the 

 surface, consisting of a short pointed shaft and horizontal 

 circular head of extreme thinness, in the centre of which may 

 be seen the trifid central canal, indicating the number of 

 branches into which it subsequently becomes transformed 

 (the smallest seen measuring about l-200th in. in diameter, 

 fig. 11, «, l>), then becoming (as it grows larger) irregular in 

 form, curvilinear in outline, and finally trilobate ; after this 

 elk-horn-like and branched ; finally filigreed at the ends of 

 the branches, when that of the shaft or fourth arm also grows 

 out into this form, and the whole interlocking on all sides with 

 their neighbours, thus become inextricably mixed together, 

 but never connected by direct union {for there is no glossy 

 fibre here). Interlocking portions when fully developed rather 

 diffuse than circumscribed or globular, as they are m some 

 species. At this time this spicule may be at least l-50th in. 

 in diameter each way (or 35-lS00ths of an inch), with all 



