108 KELLIADiE. 



its valves, laying tliem on each side nearly flat, and 

 marched across the saucer by means of its foot with such 

 rapidity that ten could scarcely be counted : it seemed to 

 be considerably assisted by the large margins of the 

 mantle." M. Mittre states that it lives on the roots and 

 leaves of fuci at a depth of from three to four fathoms, 

 and looks like beautiful pearls when seen beneath the water. 

 He also observes that it is viviparous in the strictest sense 

 of the term. 



Mr. Alder, in a letter received whilst these sheets were 

 passing through the press, urges attention to the skin cover- 

 ing the shell of Galeomma. " Phillippi," he observes, 

 " mentions it ; but I think he passes it over too slightly, as 

 it appears to me to make the shell really an internal one, 

 the only instance of such among bivalves (?). In Mi/tilus 

 and Solen the horny epidermis of the shell is a continuation 

 of that of the animal, but in other respects does not diiFer 

 from the regular epidermis of shells. In Galeomma the 

 covering of the shell is a combination of the true skin, and 

 consists of two layers ; the lower of which is slightly mus- 

 cular, and under the microscope the muscles may be seen 

 interlacing each other in all directions. The outer layer is 

 granular, and is covered with tubercles, which possibly, 

 when the animal is alive, may rise into papillse. The struc- 

 ture of the shell appears peculiar." 



Phillippi, in his " Enumeratio Molluscorum Sicilise," 

 vol. ii. p. 18, states, "Epidermis in hoc genere productio 

 cutis manifesta ; etenim facile a testa sejungitur et pallio 

 adheeret." He states that the animal was first observed 

 by Scacchi. 



The specimens described are five-eighths of an inch 

 in length by nearly three-eighths in breadth ; they were 

 taken alive by Mr. Hanley in the little islet of Herm near 



