SFONGIIDA. 397 



Hub. Thursday Island, Torres Straits. 



The abrupt termination of the spicules and the stouter fibre dis- 

 tinguish this form of 0. nuda. A single dry specimen, 105 millim. 

 (44 inches) long. 



25. Cladochalina subarmigera. 

 (Plait XXXIX. iig.H; I'l.vn: XII. figs. I, V.) 



Repent, tortuous, solid, subcylindrical : stems 4 to 8 millim. in 

 diameter (2 to 4 in a dwarf form), branching dichotomously at 

 rather long intervals, somewhat flattened above. Branches of same 

 general character as stems, often increasing somewhat in diameter 

 towards apices, maximum length about 45 millim., attached at 

 various poiuts of lower surface. A few sharp poiuts 1 to 2 millim. 

 long project from sides of stem and branches here and there, espe- 

 cially in the neighbourhood of tho larger vents ; absent in some 

 specimens ; surface otherwise even. Vents numerous, in a single 

 series, 2 to G millim. apart, along upper surfaces of stem and 

 branches, circular, 1 to 2 millim. deep, 1 to 2-5 millim. in diameter ; 

 lumen cylindrical ; margins level with the flattened upper surface 

 of tho sponge. Texture in spirit compressible, elastic, tough ; 

 surface somewhat harsh to the touch ; colour umber-brown. 



Main skeleton strictly rectangular in arrangement, rather vari- 

 able in size of meshes and. diameter of fibres in different specimens ; 

 thus the distance between primaries is *28 to "77 millim., between 

 secondaries '042 to -28 millim. ; diameter of primaries -053 to "09 

 millini., of secondaries *035 to -053 millim. (in dwarf form, pri- 

 maries '035 to - 053, secondaries *023 to "035 millim.) ; fibre almost 

 entirely spicular, a very narrow horny margin alone being usually 

 discernible (rarely in the dwarf specimen) ; spicules 6- to poly- 

 serial in primaries, 3- to 5-serial in secondaries (in the dwarf form, 

 4- to 8-serial in the former, 2- to 4- in the latter). Dermal skeleton 

 of irregular wide meshes, composed of fibres of the same structure 

 as those of the main skeleton ; between these a close angular net- 

 work of fine unispicular fibre, meshes -053 to "08 millim. in diameter. 

 Horny matter of fibres amber-yellow. Sarcodc rich yellowish brown, 

 finely granular. Spicules smooth acerate, slender, almost cylindrical 

 to within three diameters of ends, whence thev taper to sharp points ; 

 size -08 by -0032 millim., -09 by -0032, -095 by -002, to -12 by 

 •002 (in different specimens). 



Hub. Warrior Peef, Alert Island, Thursday Island, Prince of 

 "Wales Channel, Torres Straits, 4-7 fms., &c. ; bottom pearl-shells 

 or sand, &c. Albany Island, X. coast of Australia, 3-4 fms. ; bot- 

 tom mud (dwarf form). 



A few spirit-specimens represent the larger form of the species, 

 one of them is 105 millim, (4| inches) in maximum extent. A small 

 specimen, 25 millim. long, is the dwarf form above mentioned. 



The species is perhaps most closely allied to Cladochalina armigera, 

 Duch. & Mich., of described species ; the surface-spines, however, 

 which are the most striking external feature of C. armigera, are 



