SILICIOUS AND HORNY SPONGES WILSON. 331 



arranged tangentially, obliquely, and radially. The spicule is also 

 very abundant in the choanosome. 



2. Large twisted rhabds (pi. 47, fig. 11, a), sometimes with oxeate, 

 sometimes with strongylate ends; about 2 mm. long, and 40 u, thick 

 at the middle. From the middle the spicule tapers gradually to- 

 ward both ends, which, as said, are in some spicules sharp, in others 

 rounded. The choanosome is filled with these spicules, so twisted 

 and intertwined as to form a very coherent mass. An abnormal 

 form of the spicule occasionally occurs, in which the axis is branched, 

 bifid or trifid, at one end. 



3. Chiasters (pi. 47, fig. 11, c), 6-8 jjl in diameter, with no (en- 

 larged) centrum and about 7-8 rays; rays cylindrical and minutely 

 spinose distally (acanthtylasters of Lendenfeld). Spicule abundant 

 on both surfaces and throughout the sponge. 



4. Oxyasters (47, fig. 11, d, d'), commonly 20-20 jx in diameter, 

 with no (enlarged) centrum and about 7 strong, sharp rays. They 

 number of rays may be reduced to 5, 4, or even 3 (triad condition). 

 As usual, the forms with fewer rays are the larger, the total di- 

 ameter sometimes reaching 50 \l with a ray length of 24 [x. Small 

 spicules ranging down to the size of the chiaster occur, doubtless 

 young stages. The oxyasters are abundant throughout the sponge. 



The difference between ectosomal and choanosomal skeleton is 

 more conspicuous in this than in other species. The shape of the 

 choanosomal megasclere is also distinctive. 



Holotype.— Oat. No. 21270, U. S. N. M. 



Genus SPONGOSORITES Topsent (1896). 



Spongosorites Topsent 1896, p. 117, 1S9S, p. 108, and Dendy 1905, p. 182, 

 plus Acanthoxifer Dendy 1905. p. 156, plus Anacanthaea Row 1911, p. 329. 



Form various, sometimes lamellate, in which case the oscula may 

 be on one face, pores on the other. Choanosomal skeleton made up 

 of oxeas, thickly and irregularly strewn. Ectosomal skeleton dense, 

 composed of oxeas usually smaller than the choanosomal spicules, 

 and variously grouped, sometimes in radial brushes, sometimes 

 tangential and forming a smooth crust. Without astrose micro- 

 scleres, but sometimes with trichodragmas. 



SPONGOSORITES SULUENSIS, new species. 

 Plate 38, fig. 8; plate 48, fig. 3. 



Two fragmentary specimens, 6 mm. thick, the larger 80 mm. by 

 55 mm. in area, both with rounded natural margin, from station 

 D5168. 



Dermal membrane of pore surface uniformly perforated with 

 small closely set pores. The main afferent canals extend in radially 

 from this surface, and are imperfectly seen through the dermal 



