﻿SPONGES. -HALLMA.N.N 22q 



not readily determinable. For example, in a pre- 

 lirninary examination of a slide preparation of the 

 spicules of the typical form, the largest spicule ob- 

 served was 360 ;< long, though subsequently others 

 up to 430 li in length were met with ; whereas 

 measurements of the spicules m situ in the surface- 

 tufts revealed individuals some of which attained to 

 480 /(.. 



(ii.) The accessory spicules are characterised by the fact 

 that they seldom exhibit more than a slight rough- 

 ness of the surface and are frequently quite smooth. 

 They are straight sub-conical styli often with a slight 

 basal knob and a slight sub-ba'sal constriction. 



(iii.) The auxiliary spicules are typically straight smooth 

 tylostyli varying in size in the different forms of the 

 species. 



Micro scleres. — 



The general information concerning the microscleres is 

 given in the diagnosis. 



Of the species of Clathria described in the present paper, 

 C. transiens approaches most nearly to C. arcicophora in the 

 conformation of its skeleton. It differs, however, from the 

 latter species in this respect, that the main fibres are not 

 distinguishable into an axial series of longitudinal fibres, and 

 a series of secondary fibres running off from these to the 

 lateral surfaces. 



Description of the Several Forms. — 



(i). Form (a); typical form (PI. xxxiii., fig. i, and figs. 

 48, 48a). 



In the single specimen the main branches are very short and 

 much compressed, whilst the secondary branches are reduced 

 to mere lobes. The surface processes are small, often indis- 

 tinct, and are sometimes elongated into short narrow ridges. 

 Branching is not confined to one plane, although the second- 

 ary branches are for the most part marginally situated on 

 the primaries. The habit of the sponge is lobate rather than 

 ramose. It measures 75 mm. in height. 



The surface is densely, though minutely, hispid with the 

 projecting points of the principal styli which terminate the 

 fibres. There is no semblance of a dermal membrane. The 

 colour in alcohol is pale yellowish grey. 



Megascleres. — 



(i.) The principal styli vary in length from (apparently 

 not less than) 130 to 480 ]i; their maximum dia- 

 meter rarelv exceeds 17 /i, but may attain to 2o;<. 



