46 



mesampliidiscs which arc abundant in the young specimen but which I failed to 

 observe in the fullgvovvn specimen. 



The large complete, and the young, somewhat macerated, specimen wore 

 both procured at the same station to the west of the Andamans in a depth of 

 435-530 m. =238-290 fths. I'lie fragment last described was also captured in 

 the vicinity of the Andamans, 11° 2.5' r," N. 92^ 47' 6" E. in a depth of 740 

 in.=405 fths. 



B. IIEXA8TJ:R0PII()RA. 



The Hexasterophora comprise those Ilexactinollida in which amphidiscs are 

 invariably absent, but hexasters nearly always present. The first family of tins 

 group we shall deal with are the 



11. l^lUPLECTKLLIDyE. 



The sponges belonging to this family are usually thin-walled tubes, more 

 rarely caliculate or honeycombed, and always possess sword-shaped hexactines in 

 the dermal membrane. 



Hoi,AS('iis F. E. Sell. 



In 1887 I establisiied the genus ILilxiHcm for the reception of certain 

 tubular Enylecldlidx without parietal apertures. To the naked eye the outer 

 surface of these sponges appears fairly smooth. On the inner surface we observe 

 a network with (piadratic meshes occupied by pit-lik(^ depressions. The u[)por 

 end of the tube is closed by a terminal sieve-plate ; the lower end appears drawn 

 out to form the basal tuft which takes root in tlie sea-bottom. Tlio s])icules are 

 never ioined by apposed silica. 



The supporting skeleton is chic^fly composed of large princi]ial pentactines, 

 or stauractines, more rarely of hexactinc^s. Triactine, diactinc and pentactino 

 comitalia are closely attached to the long and stout rays of these principal 

 spicules which form a tubular network or scaffolding with qiuidratic meshes 

 lying close to the inner, gastral surface of the tube-wall. As the sponge grows, 

 parallel layers of stout oxyhexactines, the number of which increases Avith the 

 thickness of the body-wall, make their appeai'ance. 



The external, dermal membrane is sup[)ortod by a layer of hypoderraal 

 oxyhexactines with spincd, protruding distal I'ays. To these spicules slender 

 diactine comitalia are attached. The internal, gastral membi-anc is supported 



