REPORT ON THE TETRACTINELLIDA. 
19 
jecting spicular ends, which produce the pilosityof the surface, are the cladi of protrisenes 
and anatrisenes, and the points of oxeas, but chiefly the cladi of protrisenes ; they do not 
extend, as a rule, much more than 0'25 mm. beyond the surface, though, judging from 
broken rhabdomes, some probably extend much further. 
The cladi of most of the projecting protrisenes measured in situ are 0*142 mm. long 
by 0*006 mm. in diameter, the length of the chord is 0*108 mm.; these dimensions are 
below those given in the description of spicules, which, however, were taken from selected 
largest examples. 
Chrotella macellata,^ Sollas (PI. IV. figs. 1-22). 
Chrotella macellata, Sollas, Prelim. Account, Sci. Proc. Roy. Dubl. Soc., vol. v. p., 181, 1886. 
Sponge (PI. IV. figs. 1, 2) subspherical, depressed, with a flat base; oscules more than 
one in number, each leading into a large cloacal chamber; upper surface minutely hispid, 
lower surface coarsely so, by the projection of spicules to a longer distance. Ectosome 
a cortex, not difierentiated into two layers; choanosomal mesoderm sarcenchymatous, 
flagellated chambers small, aphodal. 
Spicules. — I. Megascleres. 1. Oxea of the spicular fibres isoactinate, fusiform (PI. 
IV. fig. 3) with similar sharp ends, which sometimes however become rounded off. 
Length 5*7 mm., breadth 0*055 mm. 
2. Oxea of the interspaces between the spicular fibres, smaller than the preceding 
(PI. IV. fig. 10), somewhat curved, and only very slightly fusiform. 
3. Protrisene (PI. IV. figs. 8, 15) with short stout cladi, highly porrectate, measuring 
0*079 by 0*0197 mm.; rhabdomebut very shghtly less in diameter immediately below the 
cladome than in the middle, thence tapering gradually to a sharp but not filiform termina- 
tion, 7*95 mm. and over, by 0*0276 mm. 
4. Protrisene (PI. IV. fig. 14) with longer cladi than No. 3, 0*23 mm. long by 
0*0197 mm. thick, less porrectate; rhabdome also shorter, 2*5 by 0*0237 mm., and 
tapering from immediately below the cladome, rather rapidly, to an almost filiform 
termination. 
5. Prodiaene and promonsene (PI. IV. figs. 4, 5). Derived from the preceding by 
reduction in the number of cladi. The rhabdomes of these measure 3*49 by 0*0316 mm.; 
the cladi of the prodisene 0*44 by 0*0316 mm., and that of the promonsene 0*58 by 
0*0316 mm. These spicules present a singular appearance, owing to the relatively large 
size of their cladi and the sudden tapering of the rhabdome. 
6. Trichodal protrisene (PI. IV. figs. 6, 7). Occurring in bundles in the cloaca 
and elsewhere. 
7. Anatrisene (PI. IV. figs. 9, 13). The cladi are 0*059 mm. long by 0*0138 mm. 
^ {}, a pick-axe with one point. 
