Note on a New Deep-Sea Echiuroid, 

 Protobonellia Mitsukurii, 



noi', g. et 110V. sp. 



BY 



Iwaji Ikeda. 



In September of 1905, I had an opportunity, through the generosity 

 of Professor Mitsukuri of the Tokyo Imperial University, to examine an 

 interesting specimen of a deep-sea Echiuroid, which was obtained by Mr. 

 AoKi with a long line in the Sagami Bay at a spot 300 fathoms deep. On 

 dissecting it, I found at once that it was a new form with many points of 

 interest. I propose to institute a new genus and species on it under the 

 name of 



PROTOBONELLIA MITSUKURII 110V. g. et 110V. Sp. 



The body (in the preserved state) measures 24 mm. including the 

 proboscis which is 15 mm. in length. The body-proper is a long ovoidal 

 form, 9 mm. long and 5 mm. wide. The integument is almost colorless 

 by the action of the preserving .fluid and is so thin, smooth, and trans- 

 parent that the ventral nerve-cord and some parts of the intestinal loop shim- 

 mer through it, except the parts near the ends where 

 papillary bodies are closely set (fig. 1.). Over the 

 remaining regions the papillae are much more minute 

 and sparingly distributed. No regular arrangement is 

 detected in all of the papillae. About 1 mm. from the 

 anterior end, there are two yellow ventral hooks, each 

 ending with an inwardly curved sharp point. Both are 

 carried on a small papilla-like elevation (see fig. 1.). 

 About I mm. behind the hooks is a small depression 

 on the left side of the nerve-cord. This is the external 



Fig. I. — Ventral view 



of the specimen, X3. aperture of the single segmental organ. The anus is 



