cM.i'ARBA. II 



tl>'' Urgent excurrent c-haniU-r in Kip. 18 in shown in Figs. Zl-'2-\ <>n a 

 I II n-preaente the subgastrnl structure, and shown the evils gnmpe1 

 r.. mi. I nul partly over the excurrent chamber: the section includes the bottom 

 .li:i|ihragms and apopyles of five of the flagellated chambers The excurrent chamber 



.U 1 l<.w these apopyh-, l.ut exactly how far cannot be seen. The position of the 

 ]x>rt in the gastral layer, which is much smaller than the full extent of the excurrent 

 . h mil T. is shown by the dotted line. Fig. 22 represents the next section higher, and 

 in. -lades the top of the excurrent chamber with one apopyle ; the second apopyle 

 1 ..!,, n-nii; to flagellated rhamber K cannot U> clearly made out and has not been 

 shown, thou-_'h it mast l>e present Fig. 23 shows the same group of rhaml>ers higlu-r 

 up and Fig. '_' 4 higher still. 



Skeleton. The gastral skeleton is a dense felt of large quadriradiates, with the 

 basal rays pointing in all directions, though the majority point more or less towards 

 tin- lse of the sponge. The apical rays, which arc very sharp, project into the gastrnl 

 . u\it\. The arrangement of the spioules is shown in Fig. 26, which represents the 

 same port that is shown in Fig. 21 ; in this drawing only a certain number of the 

 >]>i. -nl's a. tiiiillv present are drawn. The large number of the distorted r spiculet is 

 rather irnmrkaMe. The articulated tubar skeleton is formed of triradiates which arc 

 bent over the distal end of the chamber, forming a thick rounded end and not a cone. 

 The tops of contiguous flagellated chambers are joined together by the fusion of their 

 skeletons, which thus form a sort of dermal cortex, cf. Fig. 20, similar to that in genus 

 Dtrmatreton. In the present species, however, the flagellated chambers are of different 

 lengths, and consequently the dermal cortex is very irregular and not clearly defined, 

 so that it seems advisable to include it in Tenthrenwle* rather than Dermatreton. 

 Roun-1 the distal ends of the chamtars there are rings of oxea which project slightly. 



The oscular skeleton differs very little from the normal gastral and dermal 

 .-k.-h-t.iii8. The quadriradiates are rather smaller than the ordinary gastral 

 quadriradiates. There is a thick fringe of hair oxea. The meshwork of flagellated 

 chambers extends right up to the oscular edge, terminating in a scolloped edge. 

 Fig. 25 represents a longitudinal section through the oscule at a point where the 

 mesh reaches the edge. 



Spicules (Fig. 27). 



The Oxea are of one sort : 



(a) Projecting oxea, 160/i to 24 OM long x 10/t to 15 M thick, slightly and 



irregularly bent, thickest towards the outer end, which is bluntly pointed ; 

 the inner end is rather more sharply pointed 



The Triradiate* are of one sort : 



(b) Alate triradiates from the body-wall and dermal cortex. Basal rays 



straight, tapering to a sharp point, 90 p to 330 M long x 9 M thick. Paired 

 rays, unequal (appearing the more so owing to folding), bent slightly 



