PANAMA SPONGES — DE LAUBENFELS 451 



This species shows practically no trace of tendency to radiate form. 

 Many specimens of Laxosuberites show a radiate form to a very sUght 

 extent but always under circumstances that lead to the suspicion that 

 the radiate tendency had been present but then supressed by environ- 

 mental conditions. L. zeteki grows frequently where other sponges 

 assume the radiate form, and it is difficult to see how its placement 

 could interfere with that result. In contrast to this, the other sponges 



O 



Figure 42.— Laxosuberites zeteki, new genus and species: Spicules, X 533 (camera lucida). a, Head or 

 larger tylostyle; 6, pointed end of same, middle portion not shown; c, head of smaller (immature) 

 tylostj'le. 



in its immediate vicinity are practically never ramose. Its intertidal 

 placement is not conducive to its habitus; instead the vigorous action 

 of the waves would tend to compel most sponges to assume a merely 

 encrusting form. In spite of tliis zeteki grows up massive with pro- 

 jections, occasionally almost ramose. For this reason there cannot 

 be assigned any close relatives to it, and it is even questionable 

 whether it should be left in the genus Laxosuberites or given another 

 genus of its own. It is a very distinctively marked species. 



The specific name is given in honor of Dr. James Zetek, of the 

 United States Department of Agriculture, Balboa, Canal Zone. 



Genus TETHYA Lamarck 



TETHYA DIPLODERMA Schmidt 



This subspherical sponge is represented in the collection by 

 U.S.N.M. no. 22203. The color in life was yellow, the consistency 

 cartilaginous. There is a cortex about SOO/x thick grown into low 

 tubercles about 500/i liigh and the same distance apart, apex to apex. 

 It is hispid, with spicules projecting nearly a millimeter. The 

 endosome is radiate, with ascending tracts of spicules about 200m 

 thick. The megascleres themselves are tylostyles, about 11 ju by 

 900/i to 14/i by 1,200m- The larger spherasters occur not at the 

 immediate surface but in the deeper layer of the cortex, and rarely 

 in the endosome, and are about 67m in diameter. The smaller asters 

 occur in the extreme outer cortex and abundantly throughout the 



