464 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



ing toward the cavity of the cup. In the substance of the sponge 

 small canals, about 0.5 mm. wide, are numerous. The ectosome of 

 the sponge appears to be perfect over the marginal region but is 

 only partially preserved over the outer surface and has disappeared 

 from the surface of the cavity. 



Desma monocrepid, more or less curved and branched and with 

 abundant tubercles; greatest length commonly about 350 [jl, thick- 

 ness of middle body 30 \i. Some tubercles are simple, but the char- 

 acteristic ones are compound, resembling irregular rosettes. The 

 desmas are firmly united; skeletal meshes rounded and frequently 

 about 100 [x wide. In the ectosome abundant developing desmas 

 are present (pi. 51, fig. 2). The smallest observed were slightly ir- 

 regular rods (fig. 2, «). These become branched through the de- 

 velopment of outgrowths (fig. 2, b). The outgrowths (clads) be- 

 come fairly long and the desma thus acquires several bold curves 

 (pi. 51. fig. 2, c; pi. 51, fig. 3), which help to bound different skeletal 

 meshes. But straighter, more elongated, forms also occur. 



The special ectosomal megascleres in the marginal region of the 

 sponge are tylostyles or styles, 385-540 by 8-10 [/., head end termi- 

 nally spinulate, tapering gradually toward the point which is blunt, 

 the spicule sometimes slightly curved. In the tylostyle form the 

 head end is only slightly enlarged. Some of the spicules lie tan- 

 gentially at the surface forming a thin crust, one layer deep. Others 

 are radial to the surface, distributed singly but at short intervals; 

 the spicules not projecting or scarcely projecting beyond the sur- 

 face ; outer end of the spicule is the basal, larger, end. 



Over the outer surface of the sponge dermal megascleres, such as 

 have just been described, are not found. In their stead are long and 

 very slender oxeas, 350-700 by 2-3 p; tapering gradually toward 

 both ends, which are sharp ; spicule often slightly curved. Some lie 

 tangent ially at the surface, but most are radial. The latter are not 

 in bunches, but distributed singly at short intervals; they penetrate 

 well into the interior and project for the most part 300-400 t* be- 

 yond the surface, looking something like long cilia. Dermal spicules 

 of the inner surface of sponge unknown. 



Holotype.— Cat. No. 21251, U.S.N. M. 



The species is evidently close to A. hu/r/insia O. Schmidt, from 

 off Havana. In this sponge (Sollas, 1888, p. 347) the desma is tuber- 

 culate; the rhabd measures 271-355 by 10 y. and is a tylostrongyle. 

 or tylostyle, or strongyle. The rhabds lie tangentially at the sur- 

 face and form a single layer: are also at light angles to the sur- 

 face, the tylote end outward and in contact with the dermal mem- 

 brane. The genus includes, besides the two forms just mentioned, 

 A. orientalis Dendy (1905, p. 101) from Ceylon. 



