DENDY— HOMOSCLEROPHORA AND ASTROTETRAXONIDA 249 



(5) Minute spherasters (fig. 3 d) ; with moderately large centrum and numerous 

 short, strongylote rays ; total diameter about 0*008 mm. 



(6) Oxyasters (fig. 3 e) ; with no centrum and about 6 or 7 long, slender, slightly 

 roughened rays, usually strongylote. Total diameter about 0-04 mm. Very abundant 

 in the choanosome. 



This species must, as already stated, be regarded as derived from some form closely 

 related to Aurora providentice by loss of the trisenes. It is also nearly related to Aurora 

 {Rhahdastrella) distincta Thiele [1900] from Ternate, differing mainly in its rough spher- 

 asters. 



Register No., Locality, &c. cxix. 12, Salomon. 



12. Aurora rowi n. sp. 

 (Plate 44, fig. 5 ; Plate 46, fig. 4.) 



The single specimen (Plate 44, fig. 5) is an irregularly rounded, massively lobose 

 sponge, attached to a calcareous nodule very much smaller than itself. (There are 

 indications that at least one other large foreign body has been removed from the surface.) 

 The specimen measures about 36 mm. in height, 41 mm. in breadth, and has a very 

 varying thickness up to about 25 mm. The surface is subglabrous ; minutely punctate 

 under a pocket lens, and has a curious crumpled appearance, with irregular meandering 

 grooves of varying depth. The oscula are of moderate but variable size, measured up 

 to 2 mm. in diameter ; few in number, scattered singly ; without prominent margins. 

 The inhalant pores are scattered singly on the surface of the sponge, each in the middle 

 of a small polygonal area. 



The colour in spirit is a uniform chocolate brown throughout. The texture is 

 compressible but resilient ; fairly compact, but with a tendency towards the inclusion 

 of rather large foreign bodies. 



The skeleton is not very dense and somewhat confused, but on the whole shows 

 a marked radial arrangement, consisting principally of very loose wisps of large oxea 

 running towards the surface. In the more superficial part of the sponge occur numerous 

 radially arranged orthotrisenes with cladi extended beneath a dermal crust of sterro- 

 spherasters and small spherasters. 



Spicules: — (l) Orthotrisenes (Plate 46, fig. 4a); shaft well developed, straight, 

 gradually sharp-pointed, measuring about 074 by 0"023 mm. Cladi unbranched, slightly 

 recurved, sharply pointed, about 0'16 mm. long. 



(2) Oxea (fig. 4 h) ; rather slender, straight or very slightly curved ; gradually and 

 sharply pointed at each end, measuring about 1"1 by 0'023 mm. 



(3) Sterrospherasters (figs. 4 c — 4 A). The full-grown spicule (fig. 4 c) is spherical, 

 with a very large, solid centrum whose surface is covered with close-set, irregular, 

 flattened protuberances, incompletely separated from one another by narrow grooves 

 which form a reticulate pattern. The diameter of the spicule is about 0'04 mm. The 

 development of this spicule is very interesting. The first stage (fig. 4 c^) is a slender- 

 rayed oxyaster, but apparently the rays may sometimes be truncated (fig. 4 d'). A distinct 



SECOND SERIES— ZOOLOGY, VOL. XVII. . 32 



