MOLLUSCA. 73 



the occupant. Oysters are considered good and whole- 

 some food, but, by most, are preferred to be eaten raw. 



The Cock's Comb (ostrea cristi galli) is almost tri- 

 angular, and has strong folds on the border of the shell, 

 which fit into each other ; it is very rare, and found only 

 in the East Indies. 



The Neptune's Box (pecten gibbus), plate 25, fig. 4, 

 is one of the handsomest of the acephala ; differs from 

 the other oysters in having the lower shell less concave 

 than the upper, and also by the ribs radiating towards 

 the margin, like the sticks of a fan. Its size is four 

 inches, cinnamon colored, with white and bluish spots; 

 this family, with other relative races, can swim, but 

 in a most singular manner. They open and shut the 

 valves incessantly, and thus give a kind of stroke to 

 the water, which propels them upward and downward, 

 but at each move furthering their course. The Nep- 

 tune's box {scallop) is found in the West Indies. Much 

 resembling it is the large Pecten Jacobea (St. James' 

 cap), about the size of a man's hand, and somewhat 

 resembles a mantle ; in the early times it was usually 

 worn as an ornament by the pilgrims who wandered to 

 the shrine of St. James di Compostella, from whence 

 it has its name. All the pectense are eatable. 



The Pearl Oyster (mytilus margaritiferus). The 

 shell is about as large as a hand, tolerably round, of a 

 blackish color outside, and pearl-like or nacreous within. 

 The flesh tastes like that of other oysters, and is com- 

 monly eaten. The pearl oyster is found principally in 

 the Persian Gulf, the seas surrounding Ceylon and 

 Japan, and on the coast of Morocco. The pearl is sup- 

 posed to be formed by a grain of sand, which, having 

 accidentally found an entrance into the shell, has become 

 4 



