386 THE OCEAN WORLD. 



brilliant. In PL. XIY., some of the most striking forms are repre- 

 sented, as in Fig. I., the Ducal Mantle (Pecten pallium), an inhab- 

 itant of the Indian Ocean, remarkable for its elegant form, its twelve 

 radiating stripes, diverging towards the circumference, the horizontal 

 furrows of its salient scales, and the striking distribution of its white 

 spots upon a bed of red and brown marble ; Fig. II., the Purple Pec- 

 ten ; Fig. III., the Coral Pecten ; Fig. IV., the Tiger Pecten ; Fig. V., 

 the Foliaceous Pecten ; and Fig. VI., the Northern Pecten. 



Fig. 175. Pecten pseudamussium (Chenu). Fig. 176. Pecten glaber (Linnaeus). 



The animal which inhabits the Pecten shell has the general form 

 of the oyster, differing however from it in a remarkable manner. 

 The edges of the mantle are furnished with multiplied fringes of simple 

 tentacles, between which we find other tentacular appendages a little 

 thicker, each terminating in a sort of small pearl, vividly coloured, to 

 which is attached a nervous thread, which has been taken for an eye. 

 Another difference : the branchiae, in place of being connected by a 

 striated lamina, as is the case in the oyster, are cut into parallel capil- 

 lary filaments, forming a free and floating fringe, and the mouth is 

 surrounded by salient many-cleft lips. 



While the oyster shell is completely fixed to its bed, the Pecten is, on 

 the contrary, perfectly free, and shifts from place to place, moving in 

 the water even with a certain amount of agility ; by smartly closing its 

 half-opened valves and forcibly expelling the water, it moves backward 

 by a sort of reaction ; this action, repeated many times, compels the 

 animal to move almost in spite of itself, and enables it to avoid danger, 

 or directs its steps towards the spot it wishes to reach. Some 



