JOURNAL OF THE COLLEGE OF SCIENCE, IMPERIAL UNIVERSITY. 

 TOKYO, JAPAN. 



VOL. XVIII., ARTICLE 7. 



Studies on the Hexactinellida. 



CONTRIBUTION IV. 

 (MosseUidce). 



By 



Isao Ijima, %•• Ph- D.. Rig. -Hah.. 

 Professor of Zoology, Imperial T'niversitv, Tokyo. 



With 23 plates. 



The Rossellidfe I define as follows : 



Lyssaeine Hexasteropliora of cup-like or sacciform 

 body; sometimes stalked; generally firmly attached 

 at base and exceptionally rooted by basal processes or 

 by tufts of basal spicules. Besides the main terminal 

 osculum, a few secondarily formed oscula may occur. 

 Ectosomal skeleton composed of small rough dermalia 

 with a variable number of rays and of large liypo- 

 dermalia. The latter are generally pentactins which 

 often show a tendency to protrude outwards in such a 

 way that the paratangentials form a veil-like covering- 

 over the dermal surface. The dermalia, when hexactinic, 

 have the distal ray not pinular but much like the rest 

 in appearance. The gastralia are generally rough 



