SILICIOUS AND HORNY SPONGES WILSON. 407 



Skeletal framework a reticulum of spiculo-fiber with a good many 

 scattered spicules. Fibers fairly compact, frequently 80-120 y. thick, 

 although thicker and slenderer ones occur; spicules cemented to- 

 gether by a small amount of spongin. Main fibers may be distin- 

 guished, although they are not conspicuously differentiated, which 

 in the axial part of the sponge pursue a longitudinal course. These 

 curve outward in the peripheral part of body, extending radially to- 

 ward the surface, where they enter and support the little conuli. 

 Meshes of skeletal reticulum 200-700 y. wide. 



The dermal membrane includes, besides the projecting ends of 

 the radial fibers, tangential spicules. These in places are scantily 

 scattered, not forming a reticulum, but in other places are grouped 

 in slender tracts, one to a few spicules thick, which form a reticulum 

 with meshes somewhat less in width than the length of a spicule. 



Oxeas, of the usual type, cylindrical — namely, beginning to taper 

 near the ends ; slightly curved ; 220-260 by 14 pi. 



Holotype.— Cut. No. 21279, U.S.N.M. 



The Albatross sponges are close to the type (Kidley and Dendy, 

 1887, p. 9), in elongated specimens of which the oscula tend to be- 

 come arranged in a row. Distinguishing marks of the variety are 

 the conulose surface, the partial development of a special dermal 

 skeleton, the presence of so many granular cells, and the color. In 

 the type the dermal membrane is supported by the projecting ends 

 of the radial fibers, but lacks other special dermal skeleton; conuli 

 are not recorded. The type is recorded from south of Cape of Good 

 Hope, Kerguelen, between Kerguelen and Heard Island (Ridley 

 and Dendy, 1887) ; Ceylon waters (Dendy, 1905, p. 145) ; Aru Is- 

 lands (Hentschel, 1912, p. 406). Varieties have been recorded from 

 between Strait of Magellan and the Falkland Islands (Ridley and 

 Dendy, 1887) ; Amboina (Topsent, 1897, p. 476) ; Ceylon waters 

 (Dendy, 1905) ; Aru Islands (Hentschel, 1912) ; off Galapagos Is- 

 lands (Wilson, 1904, p. 121). Of the varieties, compacta is recorded 

 for the Philippines by Ridley and Dendy and by Hentschel. This 

 variety differs from the type and from the Albatross specimens in 

 being stony hard and in the absence of tufts of spicules (ends of ra- 

 dial fibers) supporting the dermal membrane. 



Hentschel (1912), is inclined to regard the species as an artificial 

 congeries of forms, and it must be owned that the whole group, type 

 plus varieties, is rather vaguely delimited. 



In several Petrosia specimens the surface is described as " rough " 

 or " granular." Perhaps a closer examination will show that in some 

 of these the surface is minutely conulose, as in the variety here 

 described. 



