L5(j CEYLON PEAEL OYSTER REPORT. 



(? always) and (sometimes, at any rate) united together below. (Possibly they may 

 have been attached to a common body, but only fragmentary tubes are present in the 

 collection.) Diameter of individual tubes about (! millims. ; thickness of tube-wall 

 about 1 "25 millims. Outer surface slightly granular and very minutely hispid. Inner 

 surface with numerous very minute openings of exhalant canals. Colour (in spirit) 

 pale greyish -yellow. Texture very soft, compressible, fragile. 



The main skeleton is a very irregular but close reticulation of slender stvli, either 

 isolated or in loose bundles : with no visible spongin cement. There is no special 

 dermal skeleton. 



Spicules. (1.) Long slender styli (Plate IX., fig. 4, a, h) ; slightly curved or bent, 

 broadly and evenly rounded off at the base, sharply and more or less gradually 

 pointed at the apex ; size about 0*28 millim. by 0'005 millini. 



(2.) Trichodragmata (Plate IX., fig. 4, d); extraordinarily abundant, especially 

 beneath the outer surface, and very variable in size, sometimes forming wisp-like 

 fibres, sometimes breaking up into separate microxea (Plate IX., fig. 4, e) ; varying in 

 length from about - 02 millim. upwards, and always very slender. 



(3.) Sigmata (Plate IX., fig. 4, c) ; also extraordinarily abundant ; slender, com- 

 monly much contort, also C-shaped ; occasionally in small bundles (sigmodragmata) ; 

 length from bend to bend variable, say about 0'02 millim. 



This appears to be a very well characterized species, and I know of no other which 

 comes very near it. The immense number of microscleres is very remarkable. 



P.N. 209 (Gulf of Manaar); 324. 



Sub-family : HETEKOXYLVE. 



Haploscleridie with a dense cortex composed of radially arranged megascleres. 

 Megascleres smooth and spined oxea. Microscleres present or absent. 

 1 propose this sub-family for the reception of the genera Heteroxya, Toi*sent, and 

 Acanthoxifer, n. gen., the former of which is, apparently with very slight justification, 

 placed by its founder amongst the Tethyida?. 



Acanthoxifer, n. gen. 



Heteroxyinse with a dense spicular cortex broken up into polygonal plates by pore- 

 hearing grooves. Main skeleton a confused reticulation of oxea. Cortical 

 skeleton composed chiefly of dense brushes of oxea arranged at right angles to 

 the surface. Megascleres smooth and spined oxea. Microscleres trichodragmata. 



This remarkable genus is evidently nearly related to Topsent'r Heteroxya (45), but 

 differs in several respects, notably in the presence of trichodragmata" which indicates 

 that the true position both of Acanthoxifer and Heteroxya is amongst the Haplo- 

 scleridse and not amongst the Tethyida;, where TorsENT has placed Heteroxya. The 

 presence of the spined oxeote megascleres suggests a possible relationship to the 

 Spongillinse, 



