306 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



These commence at the extremities and their formation progresses 

 toward the center of each face. A central area on one face, cor- 

 responding to the depressed hilum of the more ordinary type of 

 sterraster, remains devoid of spines. The detailed relation of the 

 small spines, developing upon the smooth (aspidaster) stage, to the 

 original rays which determine the general shape of the spicule, has 

 not been worked out by Sollas or his successors. Possibly there is 

 no direct relation, but it is also possible that the small spines are 

 primarily serrations of the original rays. 



Again in E. discophorus Sollas (1888, p. 238) describes the ster- 

 rasters as disciform bodies in which the actines form radiating 

 ridges on the flat faces ; the faces being granulated. In E. cylindri- 

 gerus Sollas (1888, p. 240) says "the young forms of the ster- 

 raster present themselves as excessively thin, smooth disks, composed 

 of trichital actines, radiating in a single plane." 



Lendenfeld (1910&, p. 283) described in detail the aspidasters of 

 E. sollasii. They are disciform plates longer than wide; on one 

 face, a smooth, very shallow depression corresponding to the hilum 

 of the Geodia sterraster; on both faces and at the margin, short 

 rays like those of the sterraster. The center of the aspidaster is 

 granular, and from it numerous radial lines extend toward the 

 margin. The youngest aspidasters observed (p. 285) were small 

 " oval disks " composed of numerous rays, radiating predominantly 

 (exclusively?) in the horizontal plane from a granular centrum; 

 rays at first isolated, but becoming united basally as they grow in 

 length and thickness. The fusion of rays, owing to their increase 

 in thickness, finally becomes complete, the spicule acquiring a smooth 

 margin and smooth faces. " Their smoothness in this stage consti- 

 tutes the chief difference between them and the sterrasters of 

 Geodia" "Later small, spine-like protuberances make their ap- 

 pearance on the surface of the smooth young aspidaster. These 

 develop into the protruding rays" of the adult spicule. (See also 

 pp. 272, 306-307.) 



ERYLUS CORNUTUS, new species. 



Plate 37, fig. 8 ; plate 45, figs. 5, 16 ; plate 46, figs. 1, 2. 



A large fragment, from station D5275, 80 by 70 by 60 mm., no 

 doubt belonging to a cup-like form with a shallow cloacal cavity. 

 One surface of the fragment is concave and bears apertures, oscula, 

 y 2 to 1 mm. in diameter, 3-5 mm. apart. This probably represents 

 the cloacal wall. The remaining natural surface of the specimen, I 

 take it, represents the outer surface of the sponge. In its lower 

 region this surface presents no visible apertures. In its upper 

 region it presents small apertures y 2 mm. and less in diameter, 

 scattered sparsely. These are doubtless the pores. 



