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. Decajpods , having ten legs, as the Shrimp ( Crangon ), 
Fig. 257.— Swimming Crab ( Platyonychus ). 
