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CHAPTER II. 



Class I. — Crustacea, 



The animals composing this class are distinguished by 

 having the head generally confounded with the thorax, and 

 respiring by branchiae or gills placed at the sides of the body, 

 beneath the hard covering or shell in which they are in- 

 cased. The large and better knowni species are those marine 

 animals kno\Ma under the ordinary name of shell-fish, and 

 in the Linnaean system they composed two genera alone in 

 the apterous order of insects, namely, Cancer and Monocu- 

 lus. Brisson, perceiving the impropriety of allowing these 

 animals to remain amongst the true insects, first separated 

 them — forming them, together with iYieMyriapodaQ-nAArach- 

 nida — into a class intermediate between fishes and insects, 

 thus taking the first step towards a natm-al distribution of 

 the articidated animals. Fabricius and Latreille, by accu- 

 mulating many valuable materials relative to them, assisted 

 greatly towards the same end, but it is to the immortal Cu- 

 vier that we are indebted for the first separation of the Crus- 

 tacea as a class mthin its strict limits. 



Since this period Lamarck and Leach, as well as Latreille, 

 have occupied themselves in an especial manner in endea- 

 vom"ing to elucidate this class, distributing its contents into 

 various natural groups. Jurine, Strauss, Shaw, Savigny, 

 Audouin, and Milne Edwards, have studied with great suc- 

 cess the oral and internal anatomy of the Crustacea. In our 



