FAMILIES OF CYCLOMETOPA 



191 



The carapace is sub-circular, and the rostrum short and toothed. 

 Atelecyclus, European seas. 



Fam. 3. Cancridae. — The carapace is broadly oval or hexa- 

 gonal, and the flagella of the second antennae are short and not 



lengthwise. 



hairy as in the foregoing. The first antennae fold 

 Carcinus maenas on English and North European coasts. This 

 crab has become naturalised in some unexplained manner in 

 Port Phillip, Melbourne. Cancer in North Atlantic, North 

 Pacific, and along the west coast of America into the Antarctic 

 regions. C. pagurus is the British Edible Crab. 



Fam. 4 Portunidae. — The legs are flattened and adapted for 

 swimming. The first 

 antennae fold back 

 transversely. Portu- 

 nus, Atlantic and 

 Mediterranean. N'ep- 

 ticnus, Indo - Pacific. 

 Oallinectes, C. sapidus, 

 the edible blue Crab 

 of the Atlantic coasts 

 of America. Lupa 

 (Fig. 131). 



Fam. 5. Xanth- 

 idae. — The first an- 

 tennae fold trans- 

 versely, but the legs 

 are not adapted for swimming; the body is usually transversely oval. 

 This family is especially characteristic of the tropical littoral, where 

 it is very widely represented. Xantho,Actaea, Chlorodius,Pilumnus, 

 Uriphia, with U. sjnnifrons, common in the Mediterranean. 



Fam. 6. Thelphusidae (Potamonidae). — Fresh-water crabs, 

 with the branchial region very much swollen. Thelphusa (or 

 Potamon) has nearly a hundred species distributed from North 

 Australia, through Asia, Japan, the Mediterranean region, and 

 throughout Africa. Potamocarcinus in tropical America. 



Fig. 131. — Dorsal view of Lupa hastata, x 1. (From au 

 original drawing prepared for Professor Weldou.) 



Tribe 4. Oxyrhyncha. 



This section includes the Spider-crabs and related genera, 

 in which the carapace is triangular, with the apex in front 



