294 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. " 



enlarges the genus, merging in it numerous genera recognized 

 by Sollas. Dendy (1905, p. 77) extends the genus in Sollas ? 

 sense to include forms with and without a fibrous cortex, the 

 genus remaining characterized by the microscleres, euasters of 

 two kinds. Lendenfeld (1906, pp. 252-53, 264) uses the genus to 

 include forms in which the microscleres are euasters, one or two 

 kinds, with, in some species, trichodragmas (orthodragmas of Sollas, 

 dragmas of Lendenfeld) ; the genus thus including not only Stel- 

 letta in Dendy 's sense (as used here) but Myriastra Sollas (plus 

 Pilochrota Sollas, Astrella Sollas, Anthastra Sollas, Dragmastra 

 Sollas, and Aurora, Sollas. 



STELLETTA RADICIFERA, new species. 

 Plate 37, fig. 2 ; plate 45, figs. 3, 11. 13. 



D5179, one specimen. 



More or less pear-shaped, the small end representing the upper 

 end of the sponge. Height 25 mm., thickness at the middle 18 mm. 

 Upper half of body smooth ; lower half coarsely hirsute with down- 

 wardly projecting spicules, many protruding several millimeters 

 and doubtless serving as roots. Color, brown. 



A minute osculum, point-like in size, present at the apex of 

 sponge. The pores are closed but the distribution of the dermal 

 oxyasters indicates that they are scattered everywhere in the spaces 

 bounded by the cladomes of triaenes, and have a diameter in the 

 neighborhood of 40 \l. Probably in a certain physiological phase 

 definitely outlined pore-areas appear. 



The ectosome is about 140 [/. thick, largely occupied by small sub- 

 dermal cavities which are roofed over by a very thin dermal mem- 

 brane. The ectosome is not histologically differentiated into a 

 " cortex." But the deepest layer, which forms the floor of the sub- 

 dermal cavities, is noticeable as a thin, fairly compact, brownish 

 stratum, somewhat fibrous in the sense of being made up of hori- 

 zontally elongated cells. Below this stratum is a zone of com- 

 paratively large rounded cavities, and similar spaces are abundant 

 throughout the interior, there being a high ratio of cavity to solid 

 tissue. Sponge tissue is delicate. 



Closely set radial spicular bundles pass from an excentric point 

 of the interior, much nearer the upper than the lower pole, to all 

 points of the surface. There is no ""nucleus" (the "nucleus" of 

 the literature appears to be a spheroidal kernel containing prac- 

 tically no sponge tissue, made up of the inner ends of the radial 

 skeletal elements which here come together and form a compact 

 mass). 



Spicules. — (1) Dichotriaenes (pi. 45, fig. 11). The chief radial 

 spicule; cladomes at the surface supporting the dermal membrane, 



