18 ART. 4.— I. TKEDA : 



also in having only one retractor muscle, but differs from it, 

 amongst other less important points, in the shape and structure 

 of the papillœ, in the absence of contractile villi on the dorsal 

 vessel and in the jiosition of the anus in relation to the introvert. 



PHASCOLION ARTIFICIOSUS, n. sp. 



(Figs. 6, 50-55). 



Two specimens of the new species here described under the 

 above designation, were collected, July 1903, from a depth of 

 400 hiro in the Sagami Bay. They were both occupying small 

 Gastropod shells. One of them was observed by me in the 

 fresh state and is shown in Fig. 6, enlarged about 10 times. 



The aperture of the dead shell inhabited by the worm is 

 plugged with a conical mass of cemented sand having at the 

 apex a pore, out of which the introvert of the worm is partly 

 extruded (Fig. 50). When extracted from the shell, the worm- 

 body is found to be spirally twisted in accommodation to the 

 spiral of the shell. The skin is of a bluish gray (in the fresh 

 state), but bluish black on the closely set papillœ. The body 

 proper is about 1.5 cm. long and 3.-3.5 mm. thick, while the 

 introvert is about half as long and somewhat narrower (2 mm. 

 wide). The papillœ are closely distributed over the entire sur- 

 face, and vary much in size and shape in different j^arts of the 

 body. The largest are found in a narrow zone around the 

 middle of the posterior half of the body proper. Here they 

 are of a low conical shape and appear like the so-called " Haft- 



