﻿SPONGES.-HALLMANN. 



167 



frond-like In some cases the trunk may grow to a consider- 

 able size — even assuming the form of a broad, erect plate — 

 whilst the "branches" may be reduced to the proportions of 

 marginal lobes, or may be wholly absent 

 (Whitelegge. Plate xi., fig. 14a). In con- ^--,j 

 sistency the sponge is hard and tough, ^\v 

 resembling in this respect the variet\- 

 iiroKiccti. 



The fibres do not to any appreciable 

 extent form a pseudo-reticulation, as in 

 the preceding varieties, but as a rule run 

 side by side in close parallelism, and are 

 sometimes fused several together for con- 

 siderable distances, forming what might 

 be termed "compound" columns. The 

 acanthostyles are much less densely 

 crowded on the fibres than in the variety 

 areuacea, and as a consequence the cor- 

 ing spicules are always visible and show 

 themselves to consist both of oxea and 

 acanthostyles, the former predominating. 

 The ground substance is densely strewn 

 \\ith acanthostyles and oxea, of which the 

 former are in the greater abundance. 

 C3wing to the close arrangement of the 

 fibres and the multitude of spicules, the 

 skeleton is much more compact and dense 

 than in any other variety herein described 

 with the possible exception of areuacea. 

 The dermal skeleton resembles that of the 

 last-mentioned variety. 



Me^ascJcres. — 



(i.) The oxea vary in length from 160 



to 200 }i ; the stoutest are 6 ^ in diameter. 



(ii.) The principal acanthostyles attain a maximum size of 

 1 80 X 8 ;i . 



(iii.) The dermal acanthostyles are rarely less than 80 /< 

 long, and commonly exceed 100 j^; their greatest 

 length is about 120 }i and the greatest diameter 5 or 

 (rarely) 6 }i. 



Microscleres. — 



The chelce, which vary in length from 13 to 18 ^, show 

 no appreciable separation into two groups. 



Loc. — Port Jackson (Austr. Mus. Coll.). 



Fig. 34 — C. incncs- 

 tans var. levis. a 

 Principal acantho- 

 stylus. b Dermal 

 acaiithostyli. c Iso- 

 chela arcuata. 



