iSS 



CRUSTACEA EUCARIDA DECAPODA 



CHAl'. 



FJG. 130. Dorsal view of Ilia nucleus, 

 x 1. (From an original drawing pre- 

 pared for Professor Weldon.) 



tropical, and extending into the warmer temperate seas. Jbituta 

 (Fig. 129) from the Indo-Pacific. 



Fam. 2. Leucosiidae. Similar to the above, but the afferent 



openings to the gill-chambers lie 

 at the bases of the third maxilli- 

 pedes. Male openings on the 

 sternum. This family contains 

 a great number of forms, with 

 head - quarters in the tropical 

 littoral, but extending into the 

 temperate seas. Hi a in the 

 European seas. /. nucleus (Fig. 

 130) common in the Mediter- 

 ranean. Elalia in the Atlantic, 

 North Sea, and Inclo - Pacific. 

 Leucosia in Indo-Pacific. 



Fam. 3. Dorippidae. Cepha- 

 lothorax short and square. The 

 abdomen is not hidden under the 



thorax ; the antennae are large, and the last tw r o pairs of legs are 

 held dorsally, and have terminal hooked claws. Dorippe, littoral 

 in Mediterranean and Indo-Pacific, Cymonomus (Fig. 127) from 

 deep-sea of Atlantic and Mediterranean. 



Fam. 4. Raninidae. Similar to Dorippidae, but the cephalo- 

 thorax is elongated, and the legs usually have the last two 

 joints very broad. Several genera, chiefly in the deeper littoral 

 /one. Rani 'ii a dentata in the Indo-Pacific. 



Tribe 3. Cyclometopa. 



In these Crabs the carapace is circular rather than square ; 

 its frontal and lateral margins are produced into spines and there 

 is no pointed rostrum. The mouth is square, and the third 

 max illipcdes are greatly flattened and form a lid-like expansion 

 over the other oral appendages. This group includes the 

 common Shore-crab of our coasts (Carcinus maenas), the swim- 

 ming Crabs with expanded pereiopods (Portunus, Lupa, etc.), the 

 Edible Crab (Cancer pagurus), and many others. 



Corystes cassivelaunus is a Crab of doubtful affinities. It is 

 sometimes placed among the Oxyrhyncha, but, as Gurney l has 



1 Loc. cit. \\. 181. 



