SILICIOUS AND HORNY SPONGES WILSON. 287 



Genus MYRIASTRA Sollas (1888). 

 Myria&tra Sollas, 1888, p. 112. plus Pilochrota Sollas, 1SSS, p. 120. 



The ectosome is sometimes simple and collenchymatous, sometimes 

 differentiated to form a fibrous cortex. Microscleres are euasters of 

 one sort. 



Lendenfeld (1903, 1906) merges Myriastra in Stelletta O. Schmidt. 

 In this he is followed by Hentschel (1912). Dencly, on the other 

 hand, retains (1905, 1916, 1916b) the genus, in which, doubtless 

 with justice, he merges (1916) the forms which have an ectosome 

 that is differentiated into a cortex and which have been grouped 

 by many (Sollas, 1888; Wilson, 1902; Topsent, 1904; Dendy, 1905; 

 Eow, 1911; Stephens, 1912) under Pilochrota Sollas. 



MYRIASTRA CLAVOSA (Ridley). 



Plate 37, fig. 6. 



Stelletta clavosa Ridley, 18S4, p. 474. 

 Myriastra clavosa Sollas, 1888, p. 116. 



Of this well-known species, a large number of specimens were 

 taken, in different localities. All specimens spheroidal, with the 

 horizontal diameter usually somewhat greater than the vertical; 

 horizontal diameter ranging from 5 to 22 mm. The data as to 

 color differences are, as is usual with collection material, scarcely 

 more than suggestive. The color is sometimes whitish gray or 

 light brown, sometimes reddish or pinkish brown, often greenish, 

 sometimes greenish with patches of dull reddish purple. Some of 

 the specimens are with embryos. In the great majority of the 

 specimens there is a distinctly developed cloaca. 



Station D5141. Eight specimens, 8-13 mm. in diameter, inter- 

 grading between classes "with cloaca" and "without cloaca." (See 

 below.) 



D5145. Nine specimens, 8-12 mm. diameter, with distinct cloaca. 

 Seventeen specimens, 8-12 mm. in diameter, without distinct cloaca. 



D5158. About seven dozen specimens, 11-20 mm. diameter, with 

 distinct cloaca. A dozen specimens, 9-14 mm. in diameter, with- 

 out distinct cloaca. 



D5160. Twenty specimens, 13-22 mm. in diameter, with a cloaca. 

 Two sponges have fused with one another, by the side. 



D5174. Three specimens, about 10 mm. in diameter, with distinct 

 cloaca. 



D5205. Sixteen specimens, 5-10 mm. in diameter, with distinct 

 cloaca except in some of the smallest. 



D5218. Nine specimens, 18-21 mm. diameter, with a cloaca. 



The species is a common one, occurring widely in East Indian 

 waters (China Sea, Ternate, Amboina, Torres Straits, etc.) and in 



