DENDY— HOMOSCLEROPHORA AND ASTROTETRAXONIDA 237 



of the sponge and give it its characteristic cavernous appearance when cut open. In the 

 outer part of the sponge these canals often approach very close to the surface, being 

 covered in only by a thin membrane. Texture compressible, resilient, fairly compact 

 between the wide canals. Colour in spirit light yellowish grey. There are four specimens 

 in the collection ; tliree of these have each a diameter of about 40 mm., while the fourth 

 is much smaller. 



The skeleton, at any rate towards the surface, is radially arranged, consisting of 

 large, stout oxea and orthotrisenes grouped to some extent in loose, very ill-defined 

 bundles. Most of the triaenes are in the outermost portion and have their cladi 

 extended at or very near the surface. 



Spicules : — (1) Orthotrisenes (Plate 46, fig. 1 a) ; with stout, straight or nearly straight 

 shaft, usually tapering very gradually to a fine point. Cladi simple, stout, nearly 

 straight ; extended nearly at right angles to the shaft but inclined slightly forward 

 and then slightly recurved (may be slightly inclined forward again towards the apex). 

 Shaft measuring up to about 2"0 by 0"066 mm., with cladi about 0'27 by 0'066 mm. 



(2) Oxea (fig. 1 b); long, stout, fusiform, slightly and gently curved, usually gradually 

 and sharply pointed at each end ; measuring up to about 2"6 by 0'07 mm. 



(3) Oxea (fig. 1 c) ; short, slightly curved, fairly sharply pointed at each end ; 

 measuring about 0'155 by 0-0086 mm. A few of these occur scattered through the 

 choanosome; they are possibly foreign. 



(4) Chiasters (fig. 1 d) ; small, with slender, slightly tylote rays ; total diameter 

 about 0'013 mm. 



There is a good deal of fibrous tissue in the thin ectosome (only about 0'085 mm. 

 thick), but the ectosome is not very sharply differentiated from the underlying choano- 

 some and it is impossible to speak of a distinct cortex. 



This species seems to differ from most species of Myriastra in the absence of the 

 anatrisene, of which I have found no trace. Its curious cavernous character and general 

 habit are also probably very distinctive. 



Register' No., Locality, &c. vii. 5, Saya de Malha, 6.9.05, C. 15, 55 fathoms. Four 

 specimens. 



Genus Dragmastra SoUas [1888] emen(i. 



Stellettidae in which the microscleres consist of euasters and trichodragmata. 



Sollas restricts this genus to corticate species in which the middle or collenchymatous 

 layer of the cortex is crowded with trichodragmata, I have already pointed out that the 

 degree of development of the cortex in the Stellettidse is so variable, and so many transi- 

 tions occur, that it does not form a satisfactory generic character. I therefore omit all 

 reference to the cortex from the diagnosis of this genus. 



Sollas [1888] expressly excluded Carter's Stelletta lactea from the genus Dragmastra, 

 on the ground that "the orthodragmas [= trichodragmata], as stated by Carter, are 

 confined to the choanosome, and there is no necessity therefore to assign it to Drag- 

 mastra, with which it is evidently not nearly related." 



I cannot, myself, see why it is not nearly related to Dragmastra, and I find, in the 



