KEY TO FAMILIES OF BRACHYURA I3 



cc. Carapace without rostrum, usually broad, never with the 

 hepatic region greatly reduced; orbits generally well 

 enclosed. Superfam. Brachyrhyncha 



d. Carapace generally broader than long, wide and regu- 

 larly arcuated in front; lateral margins markedly 

 convergent behind. Frontal region not markedly 

 broad, generally produced horizontally in lobes or 

 teeth. 

 e. Antennules folded longitudinally, front with several 

 teeth one of which is median ; outer maxilli- 

 peds overlapping the endostome. 



Fam. Cancridae 

 ee. Antennules folded transversely or obliquely trans- 

 versely, front with or without median tooth ; 

 outer maxillipeds not overlapping endostome. 

 /. Last pair of legs usually modified for swim- 

 ming, with the last two joints very broad and 

 paddle-like. Anterolateral border sharply 

 marked off from postero-lateral. Front with 

 or without median tooth. Fam. Portunidae 

 ff. Last pair of legs not modified for swimming. 

 Antero-lateral border of carapace not sharply 

 marked off from postero-lateral. Front gen- 

 erally divided by a median notch. 



Fam. Pilumnidae 

 dd. Carapace usually quadrilateral; lateral margins nearly 

 parallel. Frontal region usually broad, bent down- 

 wards and without teeth or sharp lobes. 

 e. Carapace often more or less membranaceous ; front, 

 orbits and eye-stalks usually very small; 

 buccal frame arcuate in front. Species small, 

 generally commensal. Fam. Pinnotheridae 

 ee. Carapace hard and firm ; front, orbits and eye-stalks 

 not markedly small ; buccal frame quadrate in 

 front. 

 /. Front usually markedly broad ; eye-stalks of 

 moderate size. Fam. Grapsidae 



ff. Front of moderate width or very narrow ; eye- 

 stalks often greatly elongated. 



Fam. Ocypodidae 



