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—Svvimmiug Crab ( Platyonychus>. 
