MANUAL OF NATUKAL HISTOBY. 287 



5. Family. — Swimming-Crabs (Portunidse). Cara- 



pace trapeziform, slightly elevated ; fore-legs 

 very long and spiny, hind legs natatory, 

 with flattened tarsi ; third joint of outer 

 foot-jaws strongly truncate at its front outer 

 angle. 



6. Family. — Freshwater-Crabs (Thelphusidse). Ca- 



rapace wider than long, straight anteriorly ; 

 eye-peduncles thick, short; fourth joint of 

 outer foot-jaws never inserted at outer angle 

 of the preceding joint; fore-legs strong, longer 

 than the others. 



7. Family. — Land-Crabs (Gecarcinidse). Carapace 



transversely oval, rounded and tumid at the 

 sides, front wide, recurved ; eye-peduncles 

 moderate ; fourth joint of outer foot-jaws in- 

 serted at outer angle of the preceding joint ; 

 fore-legs long and stout ; lining membrane 

 of gill-cavity spongy. 



8. Family. — Pea-Crabs (Pinnotheridse). Carapace 



soft, circular, front very narrow; eyes small; 

 fourth joint of external foot-jaws inserted at 

 outer angle of the third joint. 



9. Family. — Sand-Crabs (Myctiridse). Carapace 



thin, flattened, or globular, front narrow, 

 strongly inclined ; eyes small, short, not fold- 

 ing in the orbits ; inner antennae small ; outer 

 foot-jaws long and narrow, or vertical and 

 forming a cone-shaped cavity. 



10. Family. — Horseman-Crabs (Ocypodidae). Cara- 



pace quadrilateral or rhomboidal ; eye-pedun- 



