492 ZOOLOGY. 



appendages, furnished with cilia, and composed of a great 

 number of joints. These kinds of arms or cirrhi, numbering 

 twelve pairs, are curved on themselves, and the animal con- 

 stantly protrudes and withdraws them by the opening of its 

 sheath or case. At the extremity of this series of organs is 

 found a kind of tail, having the form of a long fleshy tentacle, 

 at the base of which is the anus. Their nervous system is 

 composed of a double chain of ganglions, disposed exactly as 

 in the other articulated animals. They have a heart, lodged 

 in the dorsal part of their body, and they breathe by branchiaa 

 whose form varies. 



The cirrhipeda are divided into two families the anatifse 

 and the balani. 



The Anatifas (Fig. 521) called also lepas anatifera and 

 Barnacle are enclosed in a kind of compressed mantle, open 

 on one side, and suspended by a long fleshy peduncle ; some- 

 times this mantle is almost entirely cartilaginous : at other 

 times it is covered by five testaceous plates, of which the two 

 principal ones bear some resemblance to those of a mussel. 

 The common anatifa dwells in our seas, and is frequently 

 found attached to rocks, to the keels of ships, and to pieces of 

 floating timber. It has been the subject 

 of most absurd fables ; some coarse resem- 

 blance of its shell to a bird gave origin to 

 the silly tale that from these animals came 

 the goose called barnacle. 



The Balani or sea acorns (Fig. 522) abound 

 on the rocks of our seas, and are contained 



Fig. 522. Balanus, wh . oll 7 in a , ki ? d of shell generally conical, 

 or Acorn Shell, and very snort, nxecl by its base, and com- 

 posed of several lappets articulated with 

 each other : the opening of this tube is occupied by two or four 

 moveable valves, between which is found a fissure destined to 

 give passage to the cirrhi. 



581. Finally, the division of Crustacea called xipho- 

 sura is composed only of a single genus, that of the limulus, 

 whose structure is most anomalous. These are large crus- 

 tacea, whose bodies are divided into two parts; the first, 

 covered by a semicircular buckler, has eyes, antennae, and six 

 pairs of feet surrounding the mouth, which serve at the same 

 time for walking and for mastication (Fig. 142) ; the second 

 portion of the body, covered by another buckler, almost 

 triangular, carries beneath, five pairs of swimming limbs, 



