Menippe mercenaria, a member of the family Xanthidae, is the largest xanthid species in its region (Williams 1984). The Florida stone crab has a large crusher claw with an enlarged basal tooth. The smaller pincer claw has many small teeth that can be used for cutting (Simonson 1985). The adults appear dark brownish-red in color or less mottled with dusky grey spots. The walking legs are reddish with yellow bands. Juvenile appear dark purplish-blue and have a white spot on the carpus when they are very young (Williams 1984).