CLASS CRUSTACEA. 



53 



FIG. 81. 



FIG. 82. 



Naupliue of Barnacle. 

 (Magnified.) 



Bal'dn-us balanoi'des. Acorn Bar- 

 nacle. One with its arms extended ; 

 one closed in its shell, and circular 

 scar showing the attachment of a 

 third. 



FIG. 83. 



ORDER CIRRIPEDIA (sir rl pe'dl a). 



The Barnacles, Cirriped (slr'ri ped) Crustaceans, are 



classified in all the 



older zoologies 



with the Mollusca. 



The discovery of 



the young, a free 



Nauplius, unites 



them with the 



Crustacea. As the 

 Nauplius grows, the anterior pair 

 of appendages become attached to some support, when, 

 by a series of moults, the entire struct- 

 ure of the body is changed. It becomes 

 surrounded by a more or less valved, 

 calcareous shell, from which the ani- 

 mal can at will project six pairs of 

 modified thoracic feet, which secure 

 particles of food and direct them to 

 the mouth. The Acorn Barnacles are 

 sessile (ses'sii), often covering the rocks 

 along the coast, and appearing at low 

 tide as a broad band of white. In this 

 fixed condition, they remain ever after 



Le'pasanafif'Zra. Goose 



their nauplius stage, being cemented Bamacie. onesideofsheii 



- . m , removed, showing the in- 



directly to their support. They are dosed soft parts. a , Posi- 

 not infrequently found on the shells ^nateTt' long^: 

 of larger crustaceans, marine turtles, 

 and even whales. 



The Stalked, or Goose Barnacles, 

 are pedunculate, having the delicate shell supported at 

 the extremity of a flexible stem, which in some forms 



M- 



ments. M, Muscle which 

 closes the shell. S, Stalk, 

 by means of which the ani- 

 mal attaches itself. 



