APPENDIX TO CHAPTER VII 123 



61. Body mostly depressed ; antennae short ; 



abdomen short and folded under the cepha- 

 lothorax, with 1 to 4 pairs of appendages, 

 and usually without tail-fin [superfamily 

 Brachyura] . 



cj.. Male duct opens on thoracic plate ; ce- 

 phalothorax usually quadrangular, at 

 times transversely oval; anterior lateral 

 area (liver area) of carapace small ; 

 usually fewer than 9 pairs of gills; orbits 

 look forward or obliquely downward . Catometopa 



(Square Crabs ; Fiddler-crabs) 

 c 2 . Female opening on broad thoracic plate ; 

 male opening on coxa of 5th pair of 

 thoracic legs ; 9 pairs of gills. 

 di. Cephalothorax broad, diminished be- 

 hind, bowed in front ; liver area 

 large ; orbits directed obliquely up- 

 ward and forward . .. -. .. Cyclometopa 



(Arched Crabs) 



d-2. Cephalothorax triangular, anteriorly 

 pointed, with longer or shorter ros- 

 trum ; liver area small ; orbits di- 

 rected outward . . . . Oxyrhyncha 

 (Triangular Crabs ; Spider-crab?) 



6 2 . Body mostly elongated ; antennae long ; ab- 



domen long, not bent under, or only partly 

 so, typically with 5 pairs of legs and a large 

 tail-fin [superfamily Macrura]. 

 ci. Last pair of thoracic legs shoved back- 

 ward and rudimentary. 

 di. Last thoracic segment not free ; ab- 

 domen with hard shell, hinder half 

 turned under; first pair of legs 

 typically non-chelate . , . ; Hippidce 



(Mole-crabs) 



d 2 . Last thoracic segment free ; abdomen 

 typically with thin cuticula, un- 

 symmetrical and with rudimentary 

 legs ; first pair of legs very large, 

 chelae unsymmetrical . . . Paguridce 



(Hermit-crabs) 



