CALCAREA. 35 



(//) Large alate quaclriradiates, lining the oscular tube. These are largest at 

 the junction with the Ijody-wall. Basal ray straight, tapering uniformly 

 to a very sharp point. Maximum dimensions 850 /x long x 12/a thick. 

 Paired rays bracket-shaped, equal in length, 450 /x long, oval in section, 

 16 fj. deep x 6/x thick. Oral angle, 155°; folded angle, 150°. Apical 

 ray curved orally, 100 /x long x 10/x thick. 



These get smaller up to the oscular edge, where their dimensions are as follows : 



basal ray, 150 /i. long. Paired rays, which are bent downwards, 120 /u, long 



X 10/i. thick. Apical ray reduced to a blunt cone, 20 fi long x IG/i thick. 



Subgenus GRANTIOPSIS Dendv. 



The sponge has the form of a greatly elongated hollow tube whose wall is 

 composed of two distinct layers of about equal thickness. The outer (cortical) layer 

 is provided with a very strongly developed skeleton of triradiate spicules, and is 

 penetrated by narrow ramifying incurrent canals. The inner layer is formed by 

 elongated radial chambers arranged very regularly side by side. The skeleton of the 

 inner layer is very feebly developed. The tuljar skeleton is articulate and composed 

 of very abnormal sagittal triradiates, whose paired rays are greatly reduced ; the inner 

 joint (if the tuJiar skeleton consists of cldactines. 



The above is slightly modified from Dendy's definition (7, p. 73). 



The sub-genus contains only one species. 



Grantiopsis cylixdrica Dendy. 

 (Plate XXXVI., Fig. 113.) 

 Grantiopsis cijlin'drka Dendy (7), p. 00. 



A single specimen of this species found in Australia was described by Dendy 

 (7, p- 90), who called special attention to the chiactines in its skeleton. The structure 

 of this species dift'ers considerably from that of the other species in the genus 

 Achramorpha, so that it seems advisalile to retain the sub-genus, Grantiopsis, only 

 transferring it from the Grantiidse into the Siaurorrhapkidse. 



The spicules, which have not hitherto been illustrated, are showTi in Fig. 113; 

 thev diff"er widely from any found in the new species. The sponge is fully described 

 in (7) and figured in (2). 



Megapogox. 



Staurorrhaphids in which the flagellated chambers are spherical or sac-shaped, 

 never arranged radially around the central gastral cavity, with which (or with the 

 main excurrent canals derived therefrom) they communicate by a more or less 

 complicated excurrent canal sy.stem. The skeleton of the chamber layer is largely 



