SPONGES. 89 



(7.) Chiasters ; extremely minute, with short, truncate or slightly tylote rays; 

 total diameter about 0"006 millim. ; very abundant in the dermal membrane. 



(8.) Oxyasters; of unusually large size, with no distinct centrum, with large, 

 slender, smooth, sharp-pointed rays, rather few in number ; total diameter about 

 0'0G6 millim. ; very abundant in the deeper parts of the sponge. 



There are two points in which the spiculation of Professor Herdhan's specimen, as 

 given above, diners considerably from that given by Carter (4) for the type of the 

 species. In the first place, Carter mentions no cortical oxea, but he remarks that 

 the surface is much worn, so that we need lay but little stress upon this difference. In 

 the second place, the internal oxyasters appear to be twice as large in our specimen as 

 in the type ; this also I do not consider a very important difference, as the internal 

 asters of Geoilia are subject to much variation in size. Their form, on the other 

 hand, agrees very closely in the two cases and appears to be characteristic. The 

 other spicules, also, with the exception of the sterraster, appear to be somewhat 

 larger in the present specimen ; but on the whole there can be very little doubt of 

 the correctness of the identification, especially when we remember that Mr. Carter's 

 type specimen came from the Gulf of Manaar. 



R.N. 13G (Station XLL, 12 miles off Galle, 100 fathoms). 



Sub-order: SIGMATOPHOEA. 



Tetractinellida with trirenes ; with sigmata for microscleres (when present); without 

 asters. 



Family : TETILLID^E. 



Sigmatophora with well-developed protriaenes and with skeleton usually strongly 

 radiate in arrangement. 



Tetilla, Schmidt. 



Cortex absent or feebly developed ; no special cortical skeleton. 



Tetilla hirsuta, Dexdy. 



1889, Tetilla hirsuta, Dendy (3). 

 This remarkable species is represented in the collection by three specimens which 

 differ somewhat amongst themselves, but all agree in the possession of the highly 

 characteristic, cup-shaped, poriferous pits. In all the surface is more or less strongly 

 hispid from projecting spicules, and encrusted with a layer of dirt between, to which 

 the colour of the surface is due, this colour varying with the nature of the foreign 

 matter. Two of the specimens are more or less spherical, one (R.N. 129) being 

 attached to a mass of Nullipore ; the third (E.N. 241) is constricted and slightly 

 elongated below, where it has been torn off from its attachment. In one specimen 

 (R.N. 129) there are, in addition to the characteristic spicules, a fair number of quite 

 small oxea, varying much in size, and irregularly scattered in the choanosome. Such 

 small oxea do not appear to be present in the type, but, in view of their variability 



N 



