188 PROCEEDINGS OF THE ACADEMY OP [1880. 



covered by the front ; in the Plagusinse they are received into 

 notches in the front and are visible from above. 



Analytical Key to the Genera of the Grapsidse. 



Antennse covered by the front. GRAPSIN^. 



External maxillipeds without a piliferous ridge. Grapsini. 



External maxillipeds widely gaping. 

 Antennse excluded from the orbit. 

 Meros of the external maxillipeds as long as the ischium. Goniopsis. 

 Meros of the external maxillipeds shorter than the ischium. 



Metopograpsus. 

 Antennae entering the orbit. 

 Front less than half the width of the carapax. 

 No tooth behind the orbital angle. Epigrapsus. 



One tooth behind the orbital angle. 

 Fingers of cheliped excavate. Grapsus. 



Fingers acuminate. 



Sides straight. Orthograpsus. 



Sides arcuate in front. Geograpsus. 



Two teeth behind the orbital angle. Leptograpsus. 



More than two teeth behind the angle of the orbit. 



Male abdomen five-jointed, anteunulse transverse, front 

 straight. Grapsodes. 



Male abdomen seven-jointed, antennulse oblique, front exca- 

 vate . Cyrtograpsus. 

 Front more than half the width of the carapax. 



Carapax transverse. Paehy grapsus. 



Carapax longer than broad. Nautilograpsus. 



External maxillipeds without a rhomboidal gape. 

 Palpus articulating with the inner angle of the meros of the external 

 maxillipeds. 



One tooth behind the orbital angle. Br acliy grapsus. 



Several teeth behind the orbital angle. EucMrograpsus. 



Palpus articulating with middle of the anterior margin of the meros 

 of the external maxillipeds. 



Exognath of external maxillipeds very broad. PtycJiognaihus. 

 Exognath much narrower than the ischium. 

 Sides of carapax entire. Acmceopleura. 



Sides of carapax dentate. 



External distal angle of the meros of the external maxilli- 

 peds expanded. 

 Joints of ambulatory feet rounded, dactyli styliform. 



Pseudograpsus. 

 Ambulatory feet compressed, dactyli flattened, natato- 

 rial. Varuna. 

 Meros of external maxillipeds not expanded. 



