SILICIOUS AND HORNY SPONGES WILSON. 409 



spicules cross one another in all directions producing in places, when 

 seen with a low objective, the effect of a vague, loose reticulum; but 

 there is in such places no union between the spicules and no regu- 

 larity of arrangement. 



The arrangement of the fibers and meshes of the skeletal reticulum 

 is quite irregular, although of course there are some fibers in the 

 immediate neighborhood of the surface more or less radial to it, 

 and the same is true of the walls of the largest canals. 



The dermal membrane contains a thin crust-like layer, one to a 

 few spicules thick, of tangential spicules, with some obliquely radial 

 ones; this layer shading off into the skeletal reticulum. In it the 

 spicules cross in all directions. While the skeletal reticulum reaches 

 and supports the dermal membrane, and some of the fibers are radial 

 to it, there are no fibers projecting from it. 



The spicules (pi. 49, fig. 2) are smooth, cylindrical, slightly 

 curved oxeas, 130-160 [l by 8-10 \l; rather abruptly pointed, inclin- 

 ing toward the tornote shape. A variant occurs having the shape of 

 the strongyle; those seen were shorter than the characteristic 

 spicule. 



Holotype.— Oat. No. 21281, U.S.N.M. 



The hard, smooth dermal layer, constituting a thin crust, and the 

 variable texture of the internal skeleton caused by the presence of 

 so many areas of all sizes into which the skeletal reticulum does not 

 penetrate, are the most salient characteristics of this species. 



Genus TRACHYOPSIS Dendy. 



Trachyopsis Dendy, 1905, p. 147. 

 Renierinae in which the main skeleton is composed of a dense, 

 irregular network of oxeas, while the surface is protected by similar 

 spicules arranged in vertical brushes, which support the pore-bearing 

 dermal membrane. 



TRACHYOPSIS HALICHONDRIOIDES Dendy. 



Trachyopsis halichondrioirfcs Dendy, 1905, p. 147. 



A specimen of this species from station D5218 is massive and 

 elongated, about 60 by 30 mm. There are no indications of attach- 

 ment, and the sponge may have been a " roller." The oscula are 

 not obvious; doubtless closed. There is only a single elevation cor- 

 responding to the tubular oscular processes described by Dendy 

 (1905, p. 147) ; this includes a canal, 2 mm. in diameter, extending 

 inward from the apex of the elevation. 



The very smooth surface and compact texture; the halichrondrioid 

 arrangement of the skeleton, with vague tracts radial to the surface 

 terminating in brushes of projecting oxeas; the shape of the oxea; 



