278 



ERYLUS SOLLASII. 



No correlation between the size of the sponge and the dimensions of its 

 microrhabds is discernible. The thickness of these spicules is about the 

 same in all the forms ; their length however varies, those of race III being con- 

 siderably shorter than those of the races I and II, although the specimens of some 

 of these (race I, A and B) are very much smaller. The microrhabds are 30-78 /< 

 long and 2.5-5 /i tliick. The tyle is 0.3-1.5 n thicker tliaii the adjacent parts 

 of the spicule and mea.sures 3.5-6.5 n in diameter. 



DIMENSIONS OF MICROllH.\BDS. 



The Iriaenes (Plate 1, figs. 5-26; Plate 3, figs. 16, 12, 23, 24) are ortho- 

 or, more frequently, plagio-triaenes with simple or branched clades. The 

 rhabdome is always straight. Usually it is simple and conical. Its acladomal 

 end is sharp pointed (Plate l, figs. 17, 19, 20; Plate 3, figs. 12, 23, 24) or blunt 

 (Plate 1, figs. 15, 16, 24, 26). Sometimes slight knob-like protuberances are 

 observed near the acladomal end. Rarely the rhabdome is reduced in length, 

 cylindrical, and terminally rounded and sliglitly thickened (Plate 1, fig. 18; 

 Plate 3, fig. 1). The properly developed, conical rhaljtlomes are 210-520 ji, the 



