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EXOSKELETON — 



Fiu. 9. Yeiiical section of shell or exoskeleton. 



The epidermis thrusts off successive laj-ers of its substance, which form a number of delicate 

 lamiiire superimposed upon one another, and this is impregnated with salts of lime. The 

 exoskeleton thus formed is cuticular, to be distinguished from cornified epidermis, as nails, 

 composed of modified cells, a cellular exoskeleton. 

 Classificatiok — 



Sub-Kingdom — Arthro'poda (Gr. arfJiron, a joint; pous, a foot). The body is segmented; 

 limbs jointed ; nervous system forms a ring round gullet, followed by a ventral chain of 

 ganglia. 

 Natural Order — Crustacea (L. crusta, a crust), because it breathes by gills ; has two pair of 



antenna; (lesser and greater) ; walking legs borne by thorax and abdomen. 

 Genera — Homarus, Astacus. 

 Common Names — Lobster, Craylish. 



