SILICIOUS AND HORNY SPONGES WILSON. 325 



5. Dermal spheraster (pi. 47, fig. 5,«),8[x in diameter; abundant on 

 pore and oscular surfaces, and extending for a short distance into the 

 cortical canals. Centrum large, somewhat irregular; rays short, 

 tapering to points that are not sharp; ray length considerably less 

 than diameter of centrum; number of rays rather numerous often 

 about 7-8 when seen at equatorial focus. 



6. Strongylaster of cortical canals (pi. 47, fig. 5, b) ; lining the 

 cortical canals and in the surrounding collenchyma. Centrum is 

 smaller, rays longer and more numerous than in the dermal spher- 

 aster. With an immersion objective, rays are seen to be roughened, 

 viz. most minutely spinose, terminally. Total diameter of spicule 

 12-14 n; ray length equal to or somewhat greater than diameter of 

 centrum. 



7. Oxyaster (pi. 47, fig. 5, <?), 30-32 [x in diameter; abundant 

 throughout choanosome. Centrum small, 4 [x or less in diameter, or 

 none; rays long, slender, tapering; rays few in number, 7-10. With 

 an immersion it may be seen that the rays are roughened in the 

 outer half, the roughnesses increasing in size towards the end of the 

 ray, which is therefore often not strictly pointed. The spicule makes 

 an approach to the acanthtylaster of Lendenfeld, but only a very 

 slight approach. 



Holotype.— Cat. No. 21268, U.S.N.M. 



This species is certainly very close to Geodinella robusta Lenden- 

 feld from the Pacific coast of North America (1910 p. 205), and 

 possibly should be, and with the study of more specimens may be, 

 best described as a variety of that sponge. In Lendenfeld's species, 

 based on four specimens assigned to three varieties, the cortical 

 efferent canals are uniporal, the cortical afferent canals probably 

 cribriporal. The canal system, as in the Albatross specimen, is thus 

 not different from that of Sidonops. Most of the reduced triaenes 

 are monaenes, but diaenes occur in one variety; in one variety the 

 clad of the monaene has a considerable length. Besides these and 

 oxeas, strongyles and tylotes occur. Styles or subtylostyles also 

 occur. Lendenfeld does not recognize these latter as reduced 

 triaenes, but my data establish this origin for G. splierastrosa and 

 make it probable for his species as well. As to the microscleres the 

 choanosomal asters are oxyasters scarcely differing from those of the 

 Albatross sponge. The dermal microscleres are, however, strongyl- 

 asters, instead of spherasters with tapering pointed rays. The 

 strongylaster of G. robusta is obviously the same spicule that occurs 

 in the cortical canals of the Albatross form. The tangible points of 

 difference between the two forms are, then, the character of the 

 dermal aster and the greater degree of degeneration of the triaene 

 in G. spTierastrosa. 



