188 CRUSTACEA——EUCARIDA—DECAPODA CHAP. 
tropical, and extending into the warmer temperate seas. J/atuta 
(Fig. 129) from the Indo-Pacific. 
Fam. 2. Leucosiidae—Similar to the above, but the afferent 
openings to the gill-chambers le 
at the bases of ae 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. lia in the 
European seas. J. nucleus (Fig. 
130) common in the Mediter- 
ranean. Hbalia in the Atlantic, 
North Sea, and Indo - Pacific. 
Leucosia in Indo-Pacific. 
Fra. 130.—Dorsal view of Itia nucleus, Fam. 3. Dorippidae.—Cepha- 
x1. (From an original drawing pre- 4 
pared for Professor Weldon.) lothorax short and square. The 
abdomen is not hidden under the 
thorax ; the antennae are large, and the last two pairs of legs are 
held dorsally, and have terminal hooked claws. Dovrippe, 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 
zone. Ranina 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 
maxillipedes 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 gee among the Oxyrhyncha, but, as Gurney‘ has 
toe. cit. p. 18. 
