264 



I. IKEDA. 



as long as the body proper. Similar instances are also known in Hamingia 

 arctica and H. sibogae. Lastly, it is a well proved fact that the peculiar 

 bifid proboscis of female lìoncllia arises ontogenetically from the ordinary 

 unbranched form of other Echiuroids. 



The second point to be considered in comparing the present species 

 with lìoncllia, is whether or not the sexual dimorphism found in lìoncllia 

 and Hamingia is present in the species under consideration. In order to 

 determine this interesting problem, special attention was paid, while dissec- 

 ting the pharynx and the oviduct, in the search for parasitic males that 

 might be found therein. But all my efforts were unsuccessful. Notwith- 

 standing this failure, I am inclined to believe in the sexual dimorphism of 

 the present species, because of the general agreement in anatomy of both 

 genera {Protoboncllia and Honellid), especially in regard to the structure of 

 the oviduct and to the ovarian eggs. Moreover it is not unfrequent that 

 parasitic males are not found in the female however mature this may be, as 

 for instance in lìoncllia minor as observed by myself and in Hamingia 

 sibogae as recorded by Sluiter.* 



Now, as to the affinity which the present new species bears to other 

 Echiuroids. It must be admitted that this form is remotely related to 

 the genera lichiurus and Thalasscma, but more closely to the Bonellian 

 Echiuroids. Of the latter, again, Bonellia stands more intimately allied 

 with it than any other genus. Hamingia, the only other genus of the 

 Bonellidae, agrees with the present species in having similar proboscis, 

 while it differs from the latter in wanting the ventral hooks. It may be 

 added that, two remarkable characteristics of Hamingia sibogae, as describ- 

 ed by Si.uiter, are the total absence of the anal glands and of the collateral 

 intestine. Judging from what has been said, especially with regard to the 

 proboscis and the ventral hooks, it cannot be doubted that the present 

 new species represents a very primitive type of the Eamily Bonellidae. I 

 think, therefore, it is necessary to found a new genus for this new species, 

 which I take pleasure in naming in honor of Professor Mitsukuri : 

 I 1 roioboin Ilia Mitsukurii. 



* Die Sipunculiden und Bchiuriden der Siboga-Kxpedition. Siboga-Kxiiedite XXV, 1902. 



