68 AßT. 4.— 1. IKEDA : 



THALASSEMA MUCOSUM, n. sp. 



(Figs. 20 & 98). 



Three specimens of this new species have been obtained 

 from the mudd}^ shore of Moroiso near the Misaki Marine 

 Laboratory. 



The cylindrical body in the live state reaches 7 em. in 

 length and 1.8 cm. in width ; the tubular proboscis is much 

 shorter and narrower, and has a truncated apex. The body- 

 wall is thin and is of a light green color, which becomes deeper 

 at both extremities and also along the margins of the proboscis. 

 The papillae, large enough to be visible with the naked eye, are 

 also deep green ; they are closely aggregated, especially at both 

 ends of the body proper. In the fresh state, the body-surface 

 always appears dirty owing to thick mucous spread over it. 

 The two ventral hooks are small, slightly recurved and bright 

 yellow in color. They are provided with rather short radial 

 muscles {em, Fig. 98), but are devoid of an interbasal muscle. 

 The longitudinal and circular layers of the dermal musculature 

 are not divided into separate bundles. There are three pairs of 

 comparatively short small segmental organs {sg), all of which 

 lie behind the ventral hooks and have long spiral lobes. The 

 pharynx (ph) is accompanied by two weakly developed mesen- 

 teries {wm) arising from the body-wall, close to the nerve-cord- 

 The mesentery on the right side is much longer than that on 

 the left. The neuro-intestinal vessel (ni), instead of being 



