286 COMPARATIVE ZOOLOGY. 
Wood-louse, or Sow-bug ( Oniscus), so common in damp 
places, the Slaters ( Idotea ), and the Sand-fleas ( Gammarus ), 
seen by the sea-side. 
4. Decapods , having ten legs, as the Shrimp ( Crangon ), 
Fig. 256. —Lobster (Homarus vulgaris). 
Fig. 257.—Swimming Crab ( Platyonychus ). 
