256 PERCY SLADEN TRUST EXPEDITION 



(7) Minute spherasters (fig. 3 g); with small centrum and short, strongylote (perhaps 

 sometimes tylote) rays ; total diameter about 0"008 mm. Choanosomal and dermal. 



(8) Oxyasters (fig. 3 h) ; with usually about 8 or 9 slender, minutely roughened rays 

 and inconspicuous centrum ; total diameter about 0"02 mm. 



In spiculation this species approaches Lendenfeld's Sidonops oxyastra [1910 a] pretty 

 closely, but differs in the possession of the large spherasters and perhaps in other details. 

 It also comes near to Carter's Geodia glohostellifera [1880 b], from the Gulf of Manaar, 

 which has a similar spheraster ("globostellate"), but is only 0'021 to 0'028 mm. in 

 diameter, instead of 0'05 mm. as in our species. Carter's species, however, appears 

 to have protriaenes and no anatrisenes, and the oxyasters seem to be absent. 



Eegister No., Locality, &c. lxxxvi. 1, Providence, 4.10.05, D. 4, 50 — 78 

 fathoms. 



Family Erylidse. 



Astrotetraxonida with a cortex containing aspidasters. The typical megascleres are 

 trisenes and oxea (or strongyla). The microscleres include microrhabds and choanosomal 

 euasters. 



The remarkable genus Erylus was included by SoUas [1888] in the family Geodiidse, 

 as it had been by Gray [1867 f], and this procedure has since been generally followed. 

 In 1910, however, Lendenfeld proposed to remove Erylus to a separate family by itself, 

 to which he gave the name "Erylidse." He pointed out that Erylus differs very con- 

 siderably from Geodia and proposed the name "aspidaster" for the characteristic cortical 

 spicule, which bad previously been regarded as a sterraster. This spicule is undoubtedly 

 the most characteristic feature of the Erylidse, and it is quite conceivable that, like the 

 sterrospira of Placospongia, its resemblance to the Geodia sterraster may be due simply 

 to convergence. This view is supported by the fact that Erylus differs from Geodia also 

 in other respects, such as the presence of the very characteristic microrhabd and the 

 absence of anatrieenes. The trisenes that are present seem to be less differentiated than 

 those of the Geodiidse and may resemble the short-shafted trisenes of the Pachastrellidse, 

 from primitive members of which family it seems quite possible that the Erylidse have 

 been independently and directly evolved, while the Geodiidse have almost certainly arisen 

 through the Stellettidse. 



It is customary at the present time to recognise only a single genus in this family, 

 but it seems possible that we may before long be able to sub-divide it according to the 

 form of the aspidaster. Even if we are able to do this, however, I fear that Ferrer's 

 recently proposed genus Scutastra [1912] will have to be regarded as a synonym of 

 Erylus. 



Although a good many species have been described these are for the most part 

 evidently very closely related to one another. 



Genus Erylus Gray [18671']. 

 With the characters of the family. 



