160 ART. 7. — I. IJIMA : HEXACTINELLIDA, IV. 



in diameter, though a few may be as large as mm. Those of 

 an approximately similar size lie separated from one another by 

 a space nearly equally as wide as, or sometimes much wider 

 than, their diameter. 



On the gastral side, the endosome is not developed in a 

 continuous layer, so that the excurrent canalar apertures all open 

 freely into the gastral cavity. The apertures are of various sizes, 

 some being as wide as 15 mm.; their edge is either sharp and 

 distinct or but slightly indicated. The interapertural space shows 

 an irregular interlacing of fine fibers. 



All the principal spicules are very fine, which fact accounts 

 for the soft and delicate texture of the sjoonge. The septa between 

 the two systems of canals are thin ; consequently, the sponge is 

 light, and cavernous in appearance. Its general aspect is not 

 unlike Chaunoplectella cavernosa or Aulosaccus scJmlzel. 



The species is apparently more closely allied to A. ^j/a/e-z! 

 than to A. cactus. From the former it is distinguishable by a 

 number of points, of which I may mention the relatively wider 

 canals, the freely open excurrent apertures, the smaller discoctaster 

 and the larger oxyhexaster and microdiscohexaster. 



Spiculation. 



Parenchymal diactins small, slender ; generally less than 1 

 mm. in length and at most 12 r thick. In the stalk- like base, they 

 may be over 1mm. long and 30/^ thick but can scarcely be said 

 to be coarse. Center, usually without external swelling or bosses. 

 Nearly uniformly thick throughout except at the ends which are 

 more or less swollen and rough ; extreme tip rounded. Oxyhex- 



