95 



thickenings become stouter, more clearly defined and, in the vicinity of the free 

 surfaces, more densely covered with small spines. 



The dermal hexasters are slender throughout ; their radial, distal rays are 

 pinule-like, smooth in the basal third and covered with thin not very numerous 

 spines bent obliquely outwards, which decrease in size towards the end of the 

 ray, in the distal two-thirds. 



The dermal scopules vary considerably in different individuals and also in 

 different parts of one and the same individual, but are on the whole similar to 

 those of Aphrocallistes beatrix, described and figured above. In some specimens 

 the forms with abruptly outwardly bent and terminally considerably thickened 

 branch-rays, represented in fig. 4 on plate XVI, are numerous and those with 

 rough straight, nearly cylindrical branch-rays, only slightly thickened terminally, 

 represented in fig. 5 on plate XVI, rare. In other individuals the scopules 

 with thin, slightly outwardly curved branch-rays with terminal thickenings 

 are the most numerous. I have not seen any scopules with pointed 

 branch-rays similar to those found by me in the " Challenger" material (Chal- 

 lenger Hexactinellida pi. LXXXIV, f. 5). 



As in all the other species of the genus, the gastral membrane is supported 

 by thick, tuberculous, usually straight and terminally blunt diactines or 

 stauractines. 



The uncinates also resemble those of other species. They are long, lie 

 vertical to the outer surface, and their distal ends nearly reach the latter. 



The same is to be said of the slender, parenchymal oxyhexactines, all the 

 rays of which are covered with fine, vertical spines. 



Much more peculiar and worthy of interest are the hexasters scattered in 

 varying numbers irregularly through the parenchyme. These microscleres are, 

 as in Aphrocallistes beatrix and ramosus, subject to considerable variation. Their 

 shape and size differ in different individuals, and in different regions of one and 

 the same individual, so that it will be necessary to characterise the range of 

 forms assumed by these spicules in its whole extent. I wish to state at once, 

 however, that I found oxyhexasters and onychasters in varying relative quanti- 

 ties in all specimens of Aphrocallistes bocagei. Sometimes it was difficult to 

 find even a single onychaster between the numerous oxyhexasters, sometimes 

 onychasters and oxyhexasters were present in nearly equal numbers and some- 

 times the former were more abundant than the latter. The onychasters them- 

 selves greatly vary in the length and curvature of their fine terminal claws. 

 The " regular " hexasters with six equal main-rays, forming with each other 

 right angles and terminally crowned with groups of branch-rays of the same 

 thickness, shape, number and degree of divergence, are fairly numerous. The 

 thickness of their main- and branch-rays and the number of the latter are, in 

 different spicules, however, subject to considerable variation (p. XVI, f. 6, 9). 



