156 U.S. NATIONAL MUSEUM BULLETIN 29 2 



Family Grapsidae 

 Key to the Species 



1. Front divided into three lobes by deep notches; antennules visible in dorsal 



view even when folded. Subfamily Plagusiinae. 



Plagusia depressa (p. 192) 

 Front entire; antennules hidden from dorsal view when folded 2 



2. Third maxilliped without oblique hairy ridge on exposed surface of merus . 3 

 Third maxilliped with oblique hairy ridge on exposed surface of merus. 



Subfamily Sesarminae 9 



3. Ventral margin of orbit incomplete, paralleled ventrally by deep groove and 



strong transverse crest; chelipeds very dissimilar. Subfamily Varuninae. 



Glyptograpsus jamaicensis (p. 171) 



Ventral margin of orbit entire, usually sharply produced, not paralleled 



by deep groove and supplementary crest; chelipeds similar. Subfamily 



Grapsinae 4 



4. Front abruptly deflexed at postfrontal lobes 5 



Front strongly depressed, not sharply deflexed at postfrontal lobes ... 6 



5. Carapace broadly subquadrate, front more than half as wide as carapace; 



carpus of chelipeds armed with two or three small sharp teeth on flexor 

 margin, fingers narrowly and inconspicuously spoon tipped. 



Goniopsis cruentata (p. 160) 

 Carapace subcircular in adults, front less than half as wide as carapace; 

 carpus of chelipeds armed with broad subspatulate spine-tipped tooth on 

 flexor margin, fingers broadly and conspicuously spoon tipped. 



Grapsus grapsus (p. 163) 



6. Carapace with lateral margins subparallel or converging anteriorly ... 7 

 Carapace with lateral margins converging strongly posteriorly 8 



7. Carapace with subrectangular tooth on lateral margin posterior to outer 



orbital angle, transverse striations on branchial regions only; chelipeds 

 with fingers pointed, indistinctly spoon tipped. Geograpsus lividus (p. 157) 



Carapace without tooth on lateral margin posterior to outer orbital angle, 

 strong transverse striations extending entirely across carapace; chelipeds 

 with fingers blunt, narrowly spoon tipped. . Pachygrapsus corrugatus (p. 167) 



8. Chelipeds with movable finger tuberculate on extensor margin; first pleopod 



of male broad, terminating in very short corneous tip. 



Pachygrapsus gracilis (p. 167) 

 Chelipeds with movable finger smooth; first pleopod of male slender, termi- 

 nating in long corneous obliquely T-shaped endpiece. 



Pachygrapsus transversus (p. 169) 



9. Carapace without tooth on lateral margin posterior to outer orbital angle . 10 

 Carapace with tooth on lateral margin posterior to outer orbital angle . . 18 



10. Carapace with lateral margins converging strongly posteriorly 11 



Carapace with lateral margins subparallel or diverging posteriorly, rarely 



converging slightly 12 



11. Walking legs with dactyl not more than one-fourth as long as extensor margin 



of propodus Aratus pisonii (p. 172) 



Walking legs with dactyl only sUghtly shorter than extensor margin of 

 propodus Metasesarma rubripes (p. 175) 



12. Carapace arcuate anteriorly, fronto-orbital distance considerably less than 



maximum width of carapace Cyclograpsus integer (p. 173) 



