GALEOMMA. 81 



of the gasteropods, the hinder part of the foot being then 

 unfolded into a disc ; but its favourite position is that of re- 

 pose, suspended freely in a perpendicular position, with the 

 umboes downwards, by three or four threads, so fine that 

 they cannot be seen by the naked eye, and even with a mag- 

 nifier can only be observed in certain positions of hght/^ 



It must be curious to see all this beautiful apparatus of 

 large foot, mantle spreading out widely beyond the shell, and 

 siphon and fringe of filaments suddenly withdrawn and en- 

 closed within the two flat little valves. 



The shell of L. convexa is smaller, less square, and less flat. 



Y. Galeomma Twrtoni has an oval, white, toothless shell, 

 with a very wide opening between the valves ; the foot is 

 rather cylindrical, and the mantle is studded with curious 

 tubercles. Mr. Clark having with some difficulty detached 

 a specimen from the rock, to which it was attached by the 

 byssus, kept it alive in a saucer for twenty-four hours, dur- 

 ing which time it attached and detached itself several times, 

 in one case making a new byssus, by pouring out a green 

 glutinous matter, which became a firm thread in a few mi- 

 nutes. '' When detached, it opened its valves, laying them 

 nearly flat, and marched across the saucer by means of its 

 foot, with such rapidity that scarcely ten could be counted." 



