No. 32. — 1886.] SCIENTIFIC RESEARCHES. 



303 



watched the function of this muscular bell, but we believe 

 that it very likely works as a pump for constantly renewing 

 the water in the cavity. This snail' is most probably to be 

 ranked in the system near the genus Hylina. 



The other snail lives not inside the sea-star, but upon its 

 skin ; its shell has the shape of a Phrygian. It is like the 

 other, immovably connected with the sea-star, the base of 

 its proboscis being enlarged to a disc, and this being connected 

 with the skin of the sea-star by numberless little folds. It 

 lives like the other on the body-fluid of the sea-star. 



The sea-urchins are characterised by a globular hard shell, 

 which is covered all over with spines, The regular sea* 

 urchin has the mouth at the lower pole of the spherical 

 shell, at the upper one the arms. Wyville Thomson was 

 the first to discover a sea-urchin the shell of which was 

 not hard but flexible like leather ; the spines were quite 

 short, only about a quarter to half an inch in length, and 

 surrounded by a thick skin : thus they looked like little clubs . 

 In later years a good number of other specimens have been 

 brought up from the deep sea during the expedition of the 

 "Challenger." In Trincomalee we were lucky enough to 

 discover in a depth of four to six fathoms in the harbour, 

 a beautiful new species of this group. The greatest 

 diameter of the animal was about six inches ; its height not 

 quite two inches. The colour was a dark brownish black, 

 and this ground was covered with small spines resembling 

 clubs, in consequence of the skin around them. Besides, 

 small azure corpuscles on stalks ran in radial lines from 

 the upper to the lower pole, and adorned the sea-urchin 

 like jewels. These corpuscles, as well as the other larger 

 spines, have a most striking peculiarity. If the animal is 

 taken into the hand you feel a pain as of about a dozen 

 bee-stings, which lasts for some three or four minutes, then 

 it ceases completely. The small spines as well as the blue 

 corpuscles turn against everything that approaches, and 

 from a more precise examination, the result we came to 



