326 PROF. P. M. DUNCAN ON AN 



the spinules being rather long and curved, the points looking 

 obliquely from the stem. This brush-shaped form lies with the 

 brush on the derm and not projecting (Plate XXV. fig. 8). 



Hexactinellid spicula — the four rays minutely serrate and 

 spined, not quite straight ; the lower part of the basal ray rather 

 short and attenuate, and the upper shorter, but ending in a collar 

 around a knob ; both hirsute, with minute very short spinules 

 (Plate XXV. fig. 13). 



Small, short-rayed, minutely spinulose or serrate, hexactinellid 

 spicula (Plate XXV. fig. 14). Short, stout-rayed, hexactinellid 

 spicula, with a long, fusiform, axial fibre (Plate XXV. fig. 15). 



There are also three small kinds of the ordinary quinqueradiate 

 type, the axis being prolonged as a sixth ray into a small knob ; 

 their size varies, and they form a discontinuous network within 

 the larger forms ; and many are in contact with the reticulate 

 skeleton. 



Spinulo-recurvo-polydentate spicula of exquisite delicacy. 

 The spinule is long, swollen near the head, and narrowed off at 

 the further end. The watchglass-shaped head has a fringe of 

 numerous, recurvate, long and slender processes of great tenuity ; 

 they resemble the prolongations of the rosette of Rhabdodictyon 

 delicatum, Schmidt. They are in the derm, and appear to stand 

 out from it. (Plate XXV. fig. 5.) 



Very small, multiradiate, burr-shaped rosettes. The short, 

 very linear nine or ten radii, arising from a common centre, end 

 in slight club-shaped knobs, rather thickest where they spring 

 from the radii, and bluntly spear-shaped at the end. The whole 

 is situate at the extremity of a long needle-shaped spiculum, which 

 runs into the sarcode. Some of these approach the " spinulo- 

 multifurcate sexradiate stellate " spicula of Bowerbank ; but the 

 sexradiate intermediate part is rather indistinct. They are nume- 

 rous in the derm. Others are " spinulo-trifurcate " (Plate XXV. 

 fig. 11) and " spinulo-bifurcate" (Plate XXV. fig. 12). Minute 

 sexradiates, one limb very small ; all the rest trifurcate at their 

 ends (Plate XXV. fig. 9). Larger forms, the axis being a long 

 fusiform ray extending on both sides of the plane of the four rays, 

 each of which is very small, and two are terminated by a trifid 

 extremity (Plate XXV. fig. 10). 



The projections from the thick continuous skeleton-fibres are : — 

 (1) stout at their origin, and sloping down to a fine spicule-shaped 

 process of various lengths ; (2) stout at their origin, and rather 



