SHELL-BEAHING STPUNCULUS. 253 



with all its parts expanded, as seen after preservation in 

 spirits, and the head magnified under the same circum- 

 stances. Near the junction of the trunk with the body is 

 seen the vent ; the body itself is smooth, with the excep- 

 tion of the posterior portion, where there are minute bristles 

 arranged at regular distances. The colour of the creature 

 is white, and it can extend itself to more than three inches 

 in length. The internal structure of the animal is not so 

 complicated as that of a Syrinx, and the digestive system 

 is much more simple. 



The shells selected by this Sipunculus for its habitation 

 are usually specimens of the Strombus Pes-Pelicanus, and 

 Turritella Terebra ; but I have also seen it in Littorina 

 littorea, when that shell happened to fall into sufficiently 

 deep water, and Dentalius Entalis is frequently adopted 

 by it. The parasite of the last named shell Mr. Gray 

 considers a distinct species, and has published it as such ; 

 but after examining many both living and dead, I am 

 reluctantly obliged to differ from that distinguished zoolo- 

 gist's opinion, and to regard the characters he has given as 

 dependent on accidental causes ; namely, the contraction 

 of specimens preserved in spirits, and the form of the shell 

 in which they were parasitical. 



The Sipunculus Bernhardus (I have thought proper so 

 to style it, in order to prevent the confusion arising from 

 naming it after the shell which it inhabits) is found on 

 most parts of the British coast. On the east, west, and 

 north of Scotland it is frequent ; on the coast of Ireland 

 not uncommon, and on the west and south coast of Eng- 

 land by no means rare. It lives in from ten to thirty 

 fathoms water. 



