482 " THETIS " SCIENTIFIC RESULTS. 



1 to 3mm. in diameter. Texture when wet very compressible, but 

 in the dried state brittle. Colour brown with a grey tint on the 

 trabeculse. 



Skeleton : — the primary fibres are from 0-5 to O'l mm. in 

 diameter, having about twelve or more spicules in a row ; the 

 fibres are arranged in a zig-zag manner and are separated by a 

 space equal to the length of the styli ; the main fibres present a 

 series of nodes which indicate the origin of the secondary and 

 connecting fibres. The disposition of the spicules at the nodes 

 of the network is very characteristic ; the spiny basal portion of 

 each spicule is imbedded in the spongin at every node, and the 

 acutely pointed ends are so arranged as to give a stellate or sub- 

 stellate appearance. The mesh of the sponge between the stouter 

 fibres is usually rectangular, but the reticulation is often obscured 

 by scattered spicules. 



Megascleres : — spined styli of two kinds and tornataor bluntly 

 pointed oxea. 



(i) Stout spiny styli ; the shaft is straight cylindric, with an 

 acute point, spiny base, and a few incipient spines here and there; 

 size 0-2 mm. or under, by 0-01 mm. 



(ii) Slender styli ; either smooth or with a few spines on the 

 slightly bent base ; size 0*2 mm. by 0*006 mm. 



(Hi) Tornata ; size 0-18 to 0-2 mm. by 0-004 to 0-006 mm. 



Microscleres : — sigmata both simple and contort ; size O'OIS to 

 0-025 mm. long. Isochelae rather stout : size 0-022 mm. lonsf. 



lOTROCHOTA, Ridley. 



lOTROCHOTA ARBUSCULA, sp. nov. 



(Plate xliv., fig. 18.) 



Station 41. 



Sponge stipitate; stem 75 mm. in length and 10 to 15 mm. in 

 diameter. The base is dilated, subcircular, and about 30 mm. 

 across ; the apex gives off a series of five main branches ; these 

 at a height of 30 mm. or more bifurcate, and at a distance of 

 from 40 to 80 mm. they again divide. The longer branches 

 measure 240 mm. ; at the base they exhibit slight coalescence, 

 and distally they are dichotomously divided, at least three or four 

 times ; they are mostly cylindric, but are sometimes compressed, 

 especially in the basal third ; the diameter rarely exceeds about 

 7 or 8 mm. 



