SPONGES. 227 



The spicules are nearly all regular triradiates (Plate XIII., fig. 8, ., b., c.) ; with 

 slender, not very sharply pointed rays of pretty uniform diameter and measuring 

 about 0'088 millim. in length by O'OOS millim. in diameter at the base. The apex is 

 rather abruptly and rather irregularly pointed. There are apparently no quadri- 

 radiates at all, but two (R.N. 377, 378) of the three specimens in the collection show 

 a few very slender oxea (Plate XIII., fig. 8, d) projecting from the surface of some 

 of the tubes. I have not been able to obtain these spicules in an unbroken condition, 

 but they apparently closely resemble those found in the next species ; whether or not 

 they should be regarded as constant features of this variety. I am unable to say 

 with certainty. 



R.N. 377, 378, 379 (all from Cheval Paar). 



Leucosolenia (Clathrina) tenuipilosa, n. sp.- -Plate XIII. , fig. 9. 



Sponge forming massive, reticulate colonies of ascon-tubes, closely resembling the 

 preceding variety but somewhat coarser. Here and there on the surface of the 

 colony the tubes converge to unite in small, prominent, true vents. The tubes 

 themselves are about 0'5 millim. in diameter, and they form a close reticulation 

 without any pseudoderm. The colour in alcohol is pale grey. The largest specimen 

 (R.N. 158, which may be regarded as the type of the species) is cake-shaped and 

 flattened, measuring about 47 millims. in length, 37 millims. in breadth, and 16 millims. 

 in thickness. 



The skeleton is arranged as usual in the genus, and the spicules are of three 

 kinds : 



(1.) Regular triradiates (Plate XIII., fig. 9, a), with rather stout, slightly 

 fusiform rays, bluntly and rather abruptly pointed at the apex, which is 

 often somewhat irregular. Rays measuring about O'l millim. in length by 

 0'012 millim. in diameter at the thickest part. 



(2.) Quadriradiates (Plate XIII., fig. 9, b, c) abundant ; resembling the triradiates, 

 but with an apical ray projecting at right angles into the gastral cavity. 

 This ray is somewhat variable in form and size ; typically it is long and 

 slender, gradually and sharply pointed, and slightly undulated towards the 

 extremity; in the type specimen it attains a length of about O'l 4 millim. 

 (3.) Very slender, hair-like oxea (Plate XIII., fig. 9, d). sparsely hispidating the 

 surface of the tubes. These may attain a length of more than 0'4 millim., 

 with an average diameter of only about "002 millim. They taper very 

 gradually from the proximal extremity, which is somewhat hastately sharp- 

 pointed and may be as much as 0'004 millim. thick, to the distal, which is 

 hair-like and apparently nearly always broken off. 



This species is evidently closely related to Leucosolenia conacen, var. ceylonemis, 

 but differs in the presence of the quadriradiates, and also in the greater stoutness 

 and the frequently fusiform shape of the rays of the triradiates. 



2 G 2 



