282 BULLETIN" 100, UNITED STATES NATIONAL MUSEUM. 



5. Streptaster, very variable, ranging from the plesiaster to the 

 spiraster; 16-40 y. long; all types abundant and intermingled. 

 Abundant in the dermal membrane, cloaeal wall, and canal walls; 

 less abundant in the parenchyma between the canals. The follow- 

 ing types are distinguishable : 



(a) Extreme plesiaster (pi. 45, fig. 6, a) ; total length 40 pi, ray 

 length 25 [x. number of rays 4-5, axis very short. 



(b) Plesiaster with 5-6 rays (pi. 45, fig. 6, b) ; total length 32 [x, 

 ray length 14-20 pi, axis very short. 



(c) Metaster with about 9 rays (pi. 45, fig. 6, c) ; total length 24 

 [i, ray length 12 \x ; axis short and curved. 



(d) Spiraster (pi. 45, fig. 6, d) ; total length 16-20 |x, ray length 

 6-8 pi, number of rays about 10-12; axis elongated, showing one or 

 two curves. 



Holoti/pe.— Cat. No. 21296, U.S.N.M. 



In this species the differentiation of two surfaces, virtually an 

 upper and a lower, is noticeable. One of the most marked features 

 of this differentiation concerns the radial megascleres. If we con- 

 ceive an earlier arrangement in this group to have been that of 

 radial bundles consisting of oxeas grouped round the rhabdome of 

 a triaene, as in species of Thenea, we may say that in the evolution 

 of Sphinctrella bifaeialis the radial bundles have split in two classes, 

 in one of which the triaene alone is represented, in the other only 

 the oxeas. 



Genus POECILLASTRA Sollas (1888). 



PoeciUastra Sollas, 1888, p. 79. 



Typically of plate-like form, the one surface bearing pores, the 

 other small evenly dispersed oscula. No specialized pore or oscular 

 areas. Triaenes, often rare, sometimes reduced to triods, occur at the 

 surface in the usual position, with rhabdome radial; similar triaenes, 

 or the calthrops form, are commonly present scattered in the in- 

 terior. Small oxeas, microxeas of good size, are scattered through- 

 out the sponge ; in some species smaller ones, dermal microxeas, are 

 concentrated in the ectosome. Genus extends over toward Chara- 

 cella and Pachastrella. 



PoeciUastra Sollas (1888, p. 79) is retained, with Topsent (Top- 

 sent 19026, p. 10; Wilson 1904, p. 109), in spite of the fact that it is 

 not sharply separable from Characella and PachastreUa. Several 

 authors, Lendenfeld, Dendy, Lebwohl, would merge it in Pachas- 

 treUa. But as numerous specific forms become known, what sponge 

 genera are sharply separable ( 



POECILLASTRA CILJATA, new species. 



Hat.' :;7. flg. 3; plate 4.".. figs. 8, 9. 



Station 5424, one specimen. Sponge body a lamella about 2 mm. 

 thick, probably more or less vertical in nature, 60 mm. wide, and 



