124 ART. 7. 1. IJJMA: HEXACTINELLIDA, IV. 



even much larger. The rays are somewhat more tapering towards 

 their ends ; the prickles on the surface are in like manner strongly 

 developed. Length of ray, 250-400 /i. Thickness at base, 21 /^ on 

 an average. The quadrate meshes formed by the paratangentials 

 of the gastralia measure generally 275-330 [x in length of sides. 



Special mention should be made of the fact that in the Sei. 

 Coll. specimen I have not infrequently met with paratangentially 

 disposed, diactinic gastralia, in which the aborted rays are at 

 most represented by vestigial bosses. The manner of their situa- 

 tion in company with the hexactinic form, together with the 

 nature of the prickles on the surface, leaves no doubt as to the 

 legitimacy of considering them to be gastralia. As already men- 

 tioned, they seem to be linked to the hypogastralia by means of 

 intermediate forms. But their presence in the species seems to 

 be inconstant, for in Mr. Owston's specimen I have not suc- 

 ceeded in discovering a single diactinic gastralia. 



In the specimen belonging to the Sei. Coll., a thin basidic- 

 tyonal plate is found to cover the surface of that part of the 

 coral on which it grows. The plate consists of amalgamated 

 hexactins and pentactins, arranged for the most jiart in a single 

 layer. The spicules have comparatively short rays which may l)e 

 as thick as 23 ii and whose surface shows a sparse quantity of 

 microtubercles. Several basidictyonalia were found still lying 

 loose and separate in the proximity of those that had fused to- 

 gether to form the reticular plate. 



The oxyhexaster (PL X., figs. 4-7) occurs very abundantly 

 in all parts except the ectosome. Especially plentiful is it in 

 and near the endosome. Diameter, 100-130 jj.. There exists no 



