Revision of Hexactinellids with Disc- 

 octasters, with Descriptions 

 of Five New Species. 



By Prof. I. Ijima, Ph. D. 



Zoological Institute, Science College, Imp. Univ., Tokyo. 



The discoctasters are, as enunciated by F. E. Schulze,* strongly 

 modified discohexasters in which the six principals have entirely or 

 almost entirely atrophied while the terminals have undergone a new 

 arrangement into eight secondary principals and terminal tufts at points 

 of the central node corresponding to the eight corners of a cube. This 

 peculiar kind of spicules have hitherto been known to occur in the follow- 

 ing four species of Rossellidce, viz. Accmthascus cactus, F. E. S., Bhab- 

 docalyptus mollis, F. E. S., Rh. Roeperi, F, E. S. and Rh. Dowlingi, 

 L. M. Lambe. To this list, I will add five more species, making in all 

 nine discoctasterophorous species. 



Before entering into diagnostic descriptions and systematic arrange- 

 ment of these species, I hold it essential to make, once for all, some 

 general notes on their structure. 



They are all moderately thick-walled, barrel-like, cup-like, or vase-like 

 forms with a deep gastral cavity. Frequently the body shows lateral 

 compression after it has attained a certain size. The simple osculimi is 

 situated at the upper end. The thin oscular margin is at first turned 

 inwards, but becomes later directed upwards or outwardly expanded. 

 Attachment to the substratum takes place by an irregular space at the 

 blind end, which region may be contracted in a stalk-like manner but is 

 never solid. When the sponge grows on an inclined or vertical sub- 

 stratum, it commonly happens that the basal region is bent so as to direct 

 the rest of the body upwards. 



* Sitz-ber. d. kg]. Preuss. Akad. d. Wiss., XLVI, 1893. 



