454 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



THEONELLA CYL1NDRICA, new species. 



Plate 44, fig. 4 ; plate 50, figs. 1, 2, 3. 



One specimen from station D5593. 



Sponge irregularly cylindrical, 80 mm. high, 9 to 13 mm. in trans- 

 verse diameter, bearing several protuberances, and expanded below 

 where it was probably attached. Sponge rigid; yellowish brown in 

 color. 



The dermal membrane exhibits the usual closely set, more or less 

 rounded, pore areas separated by the dermal skeletal reticulum made 

 up of overlapping clads of the phyllotriaenes. The pore areas are 

 about 150-200 [x in diameter, each including 3-6 pores. Only a single 

 osculum is to be seen, slightly less than 2 mm. in diameter, leading 

 into a small cloacal canal ; this is on the side of the sponge, upon one 

 of the protuberances. Sponge interior contains only fine canals, 0.5 

 mm. and less in diameter. There are numerous small subdermai 

 cavities. 



The ectosomal phyllotriaenes (pi. 50, fig. 1, #, b) form a single 

 layer. Rhabdome short, sharp pointed or rounded at the apex; 

 usually a little irregular ; about 100 by 22 tx. Clads variable and ir- 

 regular ; flattened and narrow ; bifurcated or not ; but typically some, 

 though not all, the clads of a spicule are bifurcated ; greatest length 

 of an entire clad about 250 jx, width 28-30 [x. Clads closely inter- 

 laced to form a firm dermal skeletal reticulum. 



The clads of the tetracrepid desmas (pi. 50, figs. 2, 3) are smooth 

 except at the ends, where zygosis takes place. Here they break up 

 into a few, short branches bearing irregular tubercles. Clads 140— 

 175 [x long, about 35 jx thick. 



The skeletal rhabds are long and slender, about 600 by 5 [x: 

 strongylate at the outer end, strongylate or tapering to a point at 

 the inner end ; chiefly in bundles that are more or less radial to the 

 surface, but there are some scattered spicules. 



The microrhabds are very small, 8 by 3 jx; rounded at the ends 

 and roughened with minute prickles; abundant in dermal mem- 

 brane and interior. 



Holotype.—C&t. No. 21305, U.S.N.M. 



In respect to habitus, the sponge approaches closest to Theonella- 

 conica (Kieschnick). But in this species (Thiele, 1900, p. 50) the 

 clads of the phyllotriaenes are not branched, and the skeletal frame- 

 work is feeble, the desmas being easily isolated. Except for the 

 habitus and the unusually small size of the microrhabds the sponge 

 would not be separable from T. swmhoei. 



