2 PROCEEDINGS OF THE NATIONAL, MUSEUM vol.76 



of California and British Columbia at depths ranging from 55 to 

 437 meters. The species is vase-shaped, as are the species in 

 general {R. plvmiodigitatus Kirkpatrick is cup-shaped), of the genus. 

 The largest specimen of R. dawsoni hitherto taken is Lambe's type, 

 about 275 mm. high. 



The sponge (pi. 1) herein described is a dried vase, widely open 

 above, about 510 mm. high, tapering somewhat toward the upper 

 (cloacal) and lower ends; cross diameter at middle of body about 

 250 mm. ; lower end irregular as if molded over the substratum ; ex- 

 treme lower end only about 55 mm. wide. Wall of vase at middle of 

 body about 22 mm. thick. Rim of cloacal aperture torn away on one 

 side; normal aperture would measure about 130 mm. in diameter. 

 Dried sponge is of a light yellowish color ; firm but fragile and very 

 light in weight. 



The autodermalia have been lost, washed or rubbed off, from almost 

 the entire surface of the body. The meshes of the hypodermal net- 

 work are therefore exposed ; they are polygonal, something less than 

 1 mm. in diameter, the intervening strands narrow. Beneath this 

 network the open ends of numerous (doubtless afferent) radial canals 

 are plainly visible. The gastral membrane is well preserved, smooth, 

 showing neat squarish meshes just visible to the eye and distinctly 

 smaller than those of the hypodermal reticulum. Beneath this mem- 

 brane the open ends of numerous radial (doubtless efferent) canals 

 may be seen as on the outer surface. 



The surface of the sponge shows many depressed areas which are 

 apparently mere accidental growth features. Some of them, as being 

 protected places, are lined with, some practically filled with, prostal 

 pentacts. Some of them contain also dense matted tufts of long pro- 

 jecting spicules (prostalia lateralia). These include many slender 

 subcylindrical diacts, in general smooth but roughened subterminally, 

 with rounded ends; characteristic spicules measure 10-17 mm. in 

 length, diameter about 12/*. Other stouter diacts occur, smooth in 

 general but roughened subterminally, tapering gradually from the 

 middle toward the slender ends which terminate in rounded or fairly 

 sharp points; characteristic spicules measured 16-19 mm. in length, 

 diameter at the middle 35;^ to 56/t. Schulze records, for the type, the 

 prostalia lateralia as consisting of prostal oxypentacts (hypoder- 

 malia, see p. 37) and smooth oxy diacts 10-15 mm. by about 40/*. 



The cloacal rim bears a marginal fringe 10-20 mm. high made up 

 of long diacts, smooth in general, roughened subterminally. Spic- 

 ules resembling the stouter ones described above and as large as 

 22 mm. by 63/* occur. The slenderer ones, many of which accompany 

 the larger as comitalia, resemble the slender diacts described above. 

 Schulze (1899) finds that the fringe in his specimens of the type is 



