478 CRUSTACEA. 



weak. Hippa eirnnta L.. lives Ijuriecl in the sea sand, Brazil. , AUmnca 

 symnista Fabr., Mediterranean. 



Fam. Paguridse. Hermit crabs. Abdomen long, usually covered with a soft 

 skin and distorted, with narrow anal fin and rudimentary abdominal feet. 

 The first pair of feet ends with powerful chela;, the two last are reduced. Some 

 of them seek shelter in empty snail shells, to protect their soft-skinned abdo- 

 minal region. Pti;/nrn>t Bernliardus L., Ccenobita rtif/nx/i Ed\v.. Birgus latro 

 Herbst, said to climb palm-trees. 



II. BEACHYURA. 



With pits for the reception of the .short internal (anterior) antennae 

 and so-called orbits, i.e., cavities for the reception of the stalked eyes. 

 Abdomen short and reduced, without caudal tin, curved round against 

 the excavated ventral surface of the thorax ; in the male narrow and 

 pointed, with only one, more rarely two pairs of abdominal feet ; in 

 the female broad, with four pairs of abdominal feet. In the female 

 each oviduct dilates to form a bursa copulatrix. The third pair of 

 maxillipeds have broad Hat joints and completely cover the anterior 

 mouth parts. The just-hatched Zocea larvae of stout shape, with 

 only two pairs of biramous feet, and a dorsal spine ; later they assume 

 the Megalopa form. Many Brachyura live on land. 



Fam. Notopoda. Transitional between the Brachyura and Macrtira. The 

 two or four posterior thoracic feet are articulated higher up than the four or three 

 posterior pairs, and shifted on to the back. The first pair of feet has large 

 chelae, the last is often modified to swimming feet. Porci-Uana platyclivlcs 

 I'eiin, Drain iii' vitlgaris Edw., LitJiodes. Latr. 



Fam. Oxystomata. With rounded cephalo-thorax. The frontal region does 

 not project. The buccal frame is triangular. The male genital openings are on the 

 basal joint of the last pair of thoracic legs. Ctiluj>i>n i/runiilatu L., Ilia nucleus 

 Herbst, Mediterranean. 



Fam. Oxyrhyncha. Cephalo-thorax usually triangular, with projecting 

 pointed rostrum. There are nine gills on either side. The male genital 

 opening is on the basal joint of the last pair of thoracic legs. The thoracic 

 ganglia are united into one mass. They do not swim but crawl. Inarlnix 

 xcurpiii Fabr.. Muju xquinadii RoncL Pi MI nnnnta Latr., Stenorhyncfi/us Lam. 



Fam. Cyclometopa. With broad, short cephalo-thorax, rounded anteriorly. 

 Without projecting frontal rostrum. There are nine gills on either side. The 

 male genital opening is on the basal jointof the last pair of thoracic legs. Some 

 of them are good swimmers. Cancer jmi/iirnx L., Xantho rirulnxux Eisso, 

 Mediterranean. Citrciniix iiKf/tux L., Pui'tunus pwber L. 



Fam. Catometopa. Quadrilatera. Cephalo-thorax quadrilateral. Frontal 

 region is curved downwards. There are fewer than nine gills. The male 

 genital openings usually lie on the sternum. Some of them live for a long 

 time away from the water. Some live in holes in the earth, as land crabs. 

 Pinni>tlirri-x jiixtun L.. in the shells of Mytilus. P. vet mini Bosc., in the shells 

 of Pi n n/i : known to the ancients, who thought that, there was a relation of 

 mutual assistance between the crab and the mollusk. (>ci/i>oiln ciirxnr Bel., 



