PBOCEEDINGS OF THE MALACOLOGICAL SOCIETY. 267 



adhering to the surface of a Synapta. The mollusc was attached by its 

 foot, which was broadened at the end, providing a circular area of contact 

 with the skin of the Holothurian. When stimulated, it did not lose its hold, 

 but the foot was drawn in and a Httle bit of the Synapta was pinched between 

 the valves of the shell. The mollusc was finally pulled away with some 

 difficulty, but there was no visible injury to the skin of the host at the 

 point of attachment. 



The mollusc was forwarded to Mr. Winckworth, who very kindly identified 

 it as Montacuta donacina, S. V. Wood. 



It was at first thought that the Montacuta had attached itself to the 

 Holothurian while being carried up to the laboratory in a bottle ; but 

 since the original observation. Dr. J. H. Orton (Marine Biol. Assoc. Plymouth) 

 has found other specimens in the same position. 



