DECAPOD CRUSTACEANS OF THE WEST INDIES 51 



7. Symmetrical, crablike decapods with loosely flexed abdomen. Marine and 



supralittoral Porcellanidae (p. 121) 



Asymmetrical hermit crabs usually found in empty gastropod shells, which 

 protect soft, twisted abdomen. Terrestrial . . . Coenobitidae (p. 123) 



8. Palp of third maxilliped articulating at or near disto mesial angle of merus, 



never concealed by expanded merus; males with spermatic duct passing 

 from coxa of fifth pereiopod to base of first pleopod; length of adult carapace 

 in midline usually not more than two-thirds of maximum width (if more 



than three-foiu"ths, anterolateral margin with 8-11 teeth) 9 



Palp of third maxilliped articulating near middle of distal margin or at dis- 

 tolateral angle of merus, occasionally partially or completely concealed by 

 expanded merus ; males with spermatic duct passing from opening in sternum 

 to base of first pleopod; length of adult carapace in midline usually at least 

 three-fourths of maximum width (if less, anterolateral margin unarmed) . 12 



9. Dactyl of fifth pereiopod either greatly compressed and expanded to form 



swimming paddle about half as wide as long or dactyls of all walking legs 



armed with rows of blunt spines 10 



Dactyls of second tlirough fifth pereiopods neither spinose nor expanded to 

 form swimming paddles 11 



10. Carapace broadly hexagonal, large spine at lateral angle; fifth pereiopods 



flattened and broadened to form swimming paddles. Marine and estuarine, 



occasionally in fresh water Portunidae (p. 127) 



Carapace broadly oval, without large lateral spine; dactyls of second tlirough 

 fifth pereiopods not expanded, armed with rows of blunt spines. In and 

 near fresh water Pseudothelphusidae (p. 136) 



11. Carapace armed with five broad anterolateral teeth, first two partially and 



broadly fused; frontal margin unarmed. Marine and supralittoral, 



especially in marshes Xanthidae (p. 153) 



Carapace armed with 8-11 small acute anterolateral teeth; frontal margin 

 armed with 15 or more small sharp spines. In and near fresh water. 



Trichodactylidae (p. 152) 



12. Third maxillipeds not gaping, almost completely covering mouth area and 



concealing mandibles when closed. Supralittoral beaches and marshes. 



OCYPODIDAE (p. 202) 



Third maxillipeds usually gaping mesially when closed, revealing at least 

 tips of mandibles (if not gaping, front of carapace deeply incised revealing 

 retracted antennules in dorsal view) 13 



13. Carapace with lateral margins well defined, either dentate or rather distinctly 



carinate. Supralittoral or near fresh water Grapsidae (p. 156) 



Carapace greatly inflated anterolaterally in adults, lateral margins not 

 sharply defined. Supralittoral and terrestrial . . Gecarcinidae (p. 194) 



Family Peivaeidae 



Subfamily Penaeinae 



Key to the Species 



1. Rostrum longer than antennal scales, without ventral teeth; dorsal antennular 

 flagellum about six times as long as antennular peduncle; basis of second 

 pereiopod unarmed; fourth and fifth pereiopods much longer than third, 

 filiform; male with petasma tubular and bearing large hornlike transverse 

 distal processes (fig. 7e) Xlphopeneus kroyeri (p. 55) 



