328 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



is no surface of attachment. The upper end of the sponge has been 

 cut away, the actual upper end of the specimen showing four canals, 

 each about 1.5 mm. in diameter, close together and descending ver- 

 tically into the sponge. The specimen is 50 mm. high, with a greatest 

 width of 18 mm. ; width of exposed upper surface 10 mm. 



Color, light brown, darker at the lower end. The ectosomal layer, 

 1.5 to 2 mm. thick, is colorless. 



Surface finely hirsute with projecting spicules, some of them pro- 

 truding 1-2 mm. The upper part of the sponge, more than half the 

 whole body, is completely covered with an incrusting Gellius about 

 2 mm. thick. Dendy's specimen from the Indian Ocean (1916, p. 

 251) was similarly incrusted with a Gelliodes, and Hentschel (1909, 

 p. 370) records that some of his specimens from the southwest coast 

 of Australia were covered with an incrusting Hymedesmia. 

 - The following data on the skeletal arrangement may be given. 

 The choanosome is thickly filled with the megascleres which are both 

 scattered and in loose tracts, the latter predominantly longitudinal. 

 The etitosomal layer contains fewer megascleres than the choano- 

 some. Somo cross it in tracts running more or less radially to the 

 surface. There are also abundant tangential megascleres just below 

 and supporting the dermal membrane. These average a smaller 

 size than the spicules of the interior. The small oxeas, about 160 [x 

 long, of the incrusting Gellius have penetrated in abundance the 

 dermal membrane of the Asteropus, lying both on and in it. 



Spicules. — 1. Oxea 2,500-3,100 by 85-100 jx, with many smaller 

 sizes down to spicules about 700 jx long. 



Sollas (1888) puts the size at 1,320 by 28 |x. Dendy records 

 for one specimen (1905) a maximum size of 1.900 by 05 [x; for 

 another (1916) 2,100 by 65 [x; for another (19166) 1,700 by 70 ;x. 

 Hentschel (1909) records a maximum of 2,525 by 72 |x. 



2. Oxyaster, abundant in the choanosome; a few in the ectosome. 

 Total diameter 40-70 [x ; no centrum ; rays commonly 5-7 in number ; 

 rays slender and tapering, roughened, but barely so, in the distal 

 portion. The spicule sometimes, especially in canal walls, may 

 closely imitate the small pentacts of the hexactinellida. 



The size and distribution of this spicule are subject to considerable 

 variation in the species. Thus in Hentschel 's specimens (1909) the 

 diameter ranges from 17 to 48 [x, and the spicule is much more abund- 

 ant in some than in other specimens. In Dendy's specimens the 

 diameter varies from 30 to 50 jx ; the spicule " scarce and easily over- 

 looked " in one specimen (1905); spicule local in distribution, so 

 as to be easily overlooked, in another (19166). 



3. Sanidaster. Abundant in dermal membrane and in walls of 

 some of the ectosomal canals ; present scantily here and there in the 



