SPONGES. 17 it 



Plocamia, Schmidt.* 



Ectyoninse of varying form ; may be encrusting or erect and branched. The 

 characteristic spicules are dumb-bell-shaped or sausage-shaped megascleres, in 

 addition to which styli or tylostyli of various forms (some of which are typically 

 echinating) may be present. The microscleres are isochelse and (at any rate 

 usually) toxa. 



Plocamia nianaarensis (Carter) Plate VIII., fig. 1. 



1880, Dictyocylindrus nianaarensis, Carter (4) ; 1 881, Dirrhopalum nianaarense, Ridley (60). 



There are several specimens of this curious sponge in the collection. Mr. Carter 

 figured and described both external form and spiculation, and Mr. Ridley added 

 valuable information on the latter point and on the question of systematic position. 

 It is therefore unnecessary for me to do much more than refer to Plate VIII. , fig. 1, 

 which represents a much finer specimen than any hitherto obtained. The colour of 

 the sponge (in spirit) varies from pale yellowish-grey to almost black,t and the 

 branching is extremely irregular. One specimen (R.N. 367) shows very clearly how 

 the main stem may be attached to the substratum by an expanded base. 



Lambe (85) lias recorded this species from California, but I think that his 

 identification is probably erroneous. 



R.N. 41 (Gulf of Manaar); 76 (Stat. XXXIII., 18 fathoms); 107 (off Galle, 

 February 13, 1902) ; 278 (deep water off Galle and onwards up West Coast of Ceylon) ; 

 367 (deep water outside pearl banks) ; 374 (Stat. LX., 20-30 fathoms, Gulf of Manaar). 



Bubaris, Gray. 



Ectyoninse of usually encrusting habit. Skeleton consisting of an inner mass of 

 diactinal (vermicular) spicules, from which large styli or tylostyli project 

 vertically outwards. Without microscleres. 



This genus was founded by Gray (31) for Bowerbank's Hymeraphia vermiculata, 

 the type of the genus Hymeraphia (H. stellifera) being a totally different sponge. 

 Topsent (59, 62) has already adopted the genus. 



It is probable that there are a large number of encrusting sponges, with skeleton 

 arrangement very similar to that of Bubaris, which are in reality not closely related 

 to one another, but derived from several groups by adaptation to an encrusting habit 

 (compare Hymedesmia amongst Astromonaxonellida). In such cases we must judge 

 of their systematic position rather by the form of the spicules than by the mere 

 arrangement of the skeleton. 



The possible relationship of the genus Bubaris to the Axinellidae is indicated in 

 the Report of the " Challenger" Monaxonida (p. 182). 



* For literature, &c, vide Ridley and Dendy (1). 

 t See footnote under lotrochota pwpwrea. 

 2 A 2 



