DENDY— HOMOSCLEROPHORA AND ASTROTETRAXONIDA 239 



This variety differs from the type of the species chiefly in the much smaller size of 

 the megascleres and in the fact that all the trigones when full-grown seem to be dichotrigenes. 

 Previously known Distribution. Devonshire coast (Carter) ; French coast (Topsent). 

 Register No., Locality, &g. cxxvi. 4 e, Mauritius, 23.8.05. 



Genus Rhabdodragma n. gen. 



Stellettidae with (? always) a very strongly developed, partly fibrous cortex. The 

 microscleres include asters, microrhabds and trichodragmata. 



This genus stands in the same relation to Sollas's Psammastra as that in which the 

 same author's Dragmastra stands to Stelletta. Stelletta includes forms without micro- 

 rhabds and without trichodragmata, while Dragmastra includes forms with trichodrag- 

 mata but no microrhabds. Psammastra includes forms with microrhabds but without 

 trichodragmata, and is perhaps indistinguishable from Ecionemia, while Rhabdodragma 

 includes forms with both microrhabds and trichodragmata, in addition, of course, to the 

 asters. 



Topsent's genus Sanidastrella [1892 d] cannot, in my opinion, be distinguished from 

 Psammastra, for the so-called sanidaster merges into the microrhabd type of spicule, as 

 the figures given by Topsent [1894 g] clearly show. 



We have here a group of usually corticate Stellettidse which are evidently all closely 

 related to one another but in which the microscleres show great variation from genus to 

 genus. The presence or absence of such distinct types of microsclere as microrhabds and 

 trichodragmata appears to me to afford good ground for generic distinction, and the same 

 may be said of the characteristic spherasters of the genus Aurora and the sterrasters of 

 the Geodiidas and Erylidae, but we cannot attribute a like value to the extremely 

 variable oxyasters (and chiasters and other related forms), as Lendenfeld [1903] has 

 done in attempting to differentiate subgenera of Stellettidse. 



Kieschnick's Psammastra conulosa from Ternate, first adequately described by 

 Thiele [1900], is the type and so far only known species of the genus, and it is extremely 

 interesting to meet with this little-known sponge again at Cargados Oarajos. 



7. Rhabdodragma conulosa (Kieschnick). 



(Plate 44, fig. 7 ; Plate 47, fig. 1.) 



Psammastra conulosa Kieschnick [1896]. 

 Psammastra conulosa Thiele [1900]. 



There are in the collection three specimens of this remarkable sponge, two 

 large and one small, all from Cargados Carajos. The type specimens, from Ternate, 

 were only about 1 cm. in diameter, but the smallest of the "Sealark" specimens has 

 a diameter of about 2 cm., while the largest has a diameter of about 6 cm., 

 being nearly as large as a cricket ball. The external appearance (Plate 44, fig. 7) 



