214 PERCY SLADEN TRUST EXPEDITION 



cannot be decided in the absence of better preserved specimens of A. irregularis. The 

 two are evidently closely related and the localities from which they were obtained 

 suggest that intermediate forms may occur at great depths in the intervening area of 

 the Indian Ocean. 



Register Nos., Localities, &c. v. 2, 4 (fragment), Saya de Malha, 7.9.1905, C. 20, 

 3 — 500 fathoms; Lxxxi., Saya de Malha, 8.9.1905, 0. 21, 450 fathoms. 



Genus Heteeorete ''■ n. gen. 



The sponge consists of thick-walled, branching, cylindrical tubes, of stony hardness. 

 The main skeleton is a stout dictyonal framework with very irregular meshes, in which 

 slender-rayed hexacts gradually become incorporated by fusion, especially in the inner 

 part of the tube-wall, where the stout dictyonal framework gives place to a much finer 

 network formed by union of the slender-rayed hexacts. The nodes of the reticulation 

 are not provided with spiny warts or with lychnisks. There are no uncinates, no scopulse 

 nor clavulse, and no pen tacts. There are discohexasters scattered in the parenchyma, 

 especially in the inner portion of the wall. The canal system is complicated by strong 

 folding of the chamber-layer and the flagellate chambers are comparatively small, oval 

 or thimble-shaped. 



This genus evidently falls into Ijima's family Dactylocalycidae. It perhaps comes 

 nearest to Dactylocalyx itself, but is remarkable for the complete absence of pentacts and, 

 indeed, of special dermal or subdermal spicules of any kind. 



2. Heterorete pulchra n. sp. 

 (Plate 41, figs. 11—18.) 



This species is represented in the collection by one good-sized fragment and a few 

 small pieces evidently belonging to the same specimen. The sponge consists of irregularly 

 branching tubes (fig. 11), about 8 mm. in diameter, and with walls about 2 mm. 

 in thickness, so that there is a wide lumen of about 4 mm. diameter. There is some 

 evidence of anastomosis between adjacent tubes, but this cannot be regarded as definitely 

 established. Both inner and outer surfaces of the tubes are mai^ked with numerous 

 small, thickly-scattered pits, representing the openings of the exhalant and inhalant 

 canals. The texture is rigid and stony, but brittle ; the colour in spirit (with the soft 

 tissues preserved) is opaque yellowish white, in the macerated condition it is glassy and 

 transparent. Numerous minute Anthozoa (? Zoanthids) are attached to the outer surface 

 of the tubes, but at wide intervals and apparently without any connection with one 

 another. Apparently they have no effect on the growth of the sponge, which does not 

 seem to respond in any way to their presence. 



The main skeleton (figs. 12, 17) is a stout dictyonal framework of cylindrical trabeculee, 

 with irregular meshes. The bars are somewhat stouter and the meshes smaller at the 

 dermal surface, where also short, conical processes are given off" from the trabecules towards 

 the dermal membrane, which they help to support. The whole of the dictyonal framework 



* This name is proposed in allusion to the two kinds of skeletal net-work. 



