490 " THETIS " SCIENTIFIC RESULTS. 



diameter. They are situated in irregular depressions and mar- 

 gined by low, rounded meandering ridges. Texture firm but 

 rather brittle ; colour 3'ellowish-grey. 



Skeleton : — stellately reticulate (Bowerbank* gives a section 

 of Halichondria incrustans, Johnston, which is the exact coun- 

 terpart of the spicular characters of the species herein described) 

 without obvious spongin. Mesh usually triangular and often 

 obscured by the presence of scattered spicules. The spicular 

 characters are rather remarkable, the choanosome is charged with 

 stout straight or slightly curved, and strongly spined styli ; the 

 ectosome and subdermal layers present a series of slender, spined 

 styli, and numerous straight cylindrical tornota with an abruptly 

 tapering point ending in a slender spine ; occasionally there are 

 oval terminations, with a trace of a spine, such as are figured by 

 Bowerbank.f The dermal surface is furnished with abundant 

 isocheliB of two sizes, and a series of c - and s-shaped spicules ; 

 the latter are scarce, but occur more or less throughout the 

 sponge. 



Megascleres : — (1) Stout, straight or slightly curved spined 

 styli, with the base somewhat dilated, and exhibiting numerous 

 spines ; the latter are continued on the shaft to within one 

 diameter of the very acute apex ; size 015 by O'Ol mm. 



(2) Slender curved spine styli ; size 0"1 by 0*005 mm. 



(3) Tornota : — straight, cylindric, ends tapering or oval, with 

 a terminal spine ; size 0'18 by 0006 mm. 



Microscleres : — large isochelse with the shaft almost straight ; 

 size 0*02 mm. Small isochelse, size O'OOl mm. Sigmata simple and 

 contort ; size 0*02 mm. 



This species is closely allied to Dendoryx {Salichondria) 

 dickiei, Bowerbank, but the spicular characters difi'er greatly. 



* Bowerbank — Mod. British Spongidae, i., 1864, pi. xxxv., fig. 323. 

 t Bowerbank — Men. British Spongidse, iii., 1874, pi. xlv., fig. 3. 



