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The sharp-nosed crabs, forming the tribe Oxystomata, are so called because the 

 carapace is produced in front into a short beak-like prominence, while the external 

 maxillipedes which cover the mouth are narrowed and pointed at the apex. The 



LONG-BEAKED SPIDER CRAB. 

 (Natural size.) 



families belonging to this group present great diversity of structure and habits, the 

 Matutidce being active swimmers and resembling the Portunida in having their pos- 

 terior legs transformed into flattened paddles, while the Calappida, which live a 

 sluggish life on the floor of the sea, have the sides of the carapace produced 



into shelf-like plates covering the legs, 

 and the upper edges of the pincers sup- 

 plied with large crests. The latter shut in 

 the cephalothorax in front, so that when at 

 rest the whole animal is inclosed in a casing 

 of shell, and resembles a smooth pebble on 

 the sea bottom. Some of the species of the 

 family Leucosiidce are remarkable for the por- 

 celain-like appearance and texture of the ca- 



DROMIA CRAB. rapace, while in others, as in Ebalia, this 



(Natural size.) plate is granular and corroded. Three or four 



