BEACH YURA. 157 



Tribe III. Brachyura. 



Abdomen little developed, bent under the body, 

 with no trace of a swimming-tail ; breast-plate 

 large between all the feet, never linear ; carapace 

 broad, and usually flat ; hind feet well developed. 



Mouth-cavity triangular ; its narrow 

 point reaching the front of the cara- 

 pace. 



Carapace generally round, or arched in 

 front, not projecting. 



Outer antennae very large ; gill-orifices 



before the first feet Corgstida>. 



Outer antennae minute ; no gill-orifices. Leucosiada*. 



Mouth-cavity very large before, and 

 remote from front. 



Carapace generally four-sided, or ovate 

 with the front nearly straight. 



Carap. four- sided ; eye-stalks very short Grapsidce. 



eye-stalks very long Gonoplacida. 

 Carapace round, as long as wide ; front 



narrow Phmotherida . 



Carapace large and regularly arched in 

 front, narrowed behind. 



Hind feet enlarged ; their last joint 

 forming a flat plate, with a fringed 



edge for swimming Portunida. 



Hind feet ending in a sharp claw . . Cancerida>. 



Carapace narrow in front, projecting into 

 a beak ; broad behind. 



First feet much the longest; hand 



three sided ; claws bent downward ; 



basal joint of outer antennae minute. Parthenopida. 

 All the feet nearly equal in length ; 



basal joint of outer antennae very 



large Maiadcc. 



All the feet very long and slender, the 



second pair much the longest . . Leptopodiada 



