JOURNAL OF THE COLLEGE OF SCIENCE, IMPERIAL UNIVERSITY, 

 TOKYO, JAPAN. 



VOL. XXI., ARTICLE 8. 



On Three New and Remarkable Species 

 of Echiuroids 



(Jioiieffia inft/(fjiniai, Thala.sseina tœnloifJes 

 and T. elef/ans). 



By 

 Iwaji Ikeda, RigahusM. 



With 4 plates. 



AYliile engaged in a study of the Gephyrean worms of Japan, 

 I liave devoted special care in examining the organization of three 

 forms which seemed to me to be very remarkable in many re- 

 spects, viz., of Bonellia miyajimai, Tlialassema tœnioides and T. 

 elegans. All the three species, considered to be new, have already 

 been described by me in short in a paper entitled " The Gephyrea 

 of Japan." ^^ I now propose in the present article to describe 

 them somewhat in detail, for which act I believe no apology is 

 needed in view of the many points of peculiarities presented by 

 them in their organization. Indeed some of their structural points 

 appear to me to be of very great significance both from the 

 systematic and the phylogenetic standpoint. The two species 

 referred to llicdassema probably deserve to be made into a new 

 and distinct genus ; l)ut for the present they may remain under 

 tlic same 2:eneric desicrnation used bv me before. 



1) Tl.is Journal, Vol. XX., Art. 4, 1904. 



