Hexactinellidse and Lithistidse. 453 



to Mr. Kent (who, as before stated, has the merit of having 

 discovered, described, and illustrated this unique specimen), 

 confirmed by my own observations, they amount to seven, 

 viz. : — 



1 and 2. The same as in Aphrocallistes Bocagei. 



3. An umbrella-like spino-capitate shaft of two forms, one 

 of which has a large , flat, convex head, plain or umbonate, 

 with a fringe of minute spines (PI. XV. fig. 4), and the other 

 a small convex head, also plain or umbonate, with a few long 

 recurved spines, microspined on the inner aspect (fig. 5) ; 

 while between these two extremes this spicule assumes several 

 intermediate forms, in all of which the shaft is pointed, more 

 or less microspined, and of whip-like fineness towards the free 

 extremity. 



N.B. This spicule, which appears to be analogous to the 

 scopuline form in the Aphrocallistidae and that of Schmidt's 

 Farrea facwida, from lying parallel with the arms of the large 

 sexradiate skeleton-spicule, often becomes enveloped with them 

 in the vitreous fibre (PI. XV. figs. 6 & 7). 



4. A rosette whose arms are five-rayed ; the rays sigmoid, 

 capitate, and somewhat expanded or divergent e?ijleur-de-lis } 

 with the head of the ray round and spined on the margin 

 (like fig. 10, PI. XIII.). 



5. A sexradiate spicule with one arm smooth and inflated, 

 the rest smooth, and terminated respectively by spiniferous 

 points (see Mr. Kent's figure 23, Month. Microscop. Journ. 

 1870, pi. My.). 



6. A sexradiate spicule with one arm spined feather-like, 

 and the rest terminated respectively by spiniferous points 

 (like fig. 9, PL XV.). 



Nos. 5 and 6 appear to be alternating forms of each other, 

 and analogous to the sexradiate spicule with one arm spined 

 feather-like in Aphrocallistes Bocagei &c, but apparently more 

 sparse and less fully developed. 



7. A simple minute sexradiate, whose arms may be smooth 

 or spined, attached by one arm to, or more or less enveloped 

 in, the vitrified fibre, as in PL XIII. fig. 1. 



Obs. These spicules all appear to be analogous to those in 

 Aphrocallistes Bocagei] while the umbrella-like ones, lying 

 para] lei and close to the arms of the large sexradiate (which 

 forms the basis of the vitrified skeleton), are often, as before 

 stated, enveloped with it (PL XV. figs. 6 & 7, b). In short, 

 as the sexradiate spicule with feather-like spined arm is seen 

 in the embryo Aphrocallistes Bocagei to be becoming enclosed 

 in the vitreous fibre of that species, so the umbrella-like 

 spicules of Aulodictyon Woodwardii may be observed on 



