544 CRUSTACEA MALACOSTRACA. 



Tribe 2. OXYSTOMATA. 



Carapace usually convex ; buccal frame triangular, the mouth cavity 

 being prolonged on either side to the front as two convergent efferent respi- 

 ratory channels containing the grooved ends of the endopodites of the 

 first maxillipeds ; the afferent openings often conspicuous, in front of 

 the bases of the chelipeds (except Leucosiidae, q.v.). Their habit is to lie 

 buried in sand, with the tip of the rostrum alone uncovered. 



Fam. 1. Dorippidae. Carapace truncated in front ; the last or last 

 two pairs of legs short, feeble, semi-prehensile and situated dorsally, as 

 in the Brachyura Anomala. Dorippe Fabr. Ethusa Roux, carapace 

 longer than broad, approaching the Macrura ; from moderate depths to 

 nearly 2,000 faths. 



Fam. 2. Leucosiidae. Afferent respiratory channels open, not be- 

 hind the pterygostomial regions, as usual, and as in other families of 

 this group, but at the antero -lateral angles of the buccal frame, whence a 

 channel leads to the base of the 3rd maxilliped. 2nd antennae 

 much reduced. Leucosia Fabr. carapace smooth, semi-globose and 

 produced anteriorly, with a pit (? nonrespiratory) in front of the bases 

 of the chelipeds. Often polished and beautifully coloured. Philyra 

 Leach. Myra Leach. Ebalia Leach, carapace sub-orbiculate, uneven. 

 Littoral and deeper waters, Atlantic and Indo-Pacific. Four British spp. 

 Ixa Leach ; Oreophorus Riippell. Acanthocarpus Stimpson, a specimen, 

 dredged by the Blake from deep water, has a stridulating apparatus on 

 the chela and carapace. 



Fam 3. Calappidae. Carapace convex, sometimes orbicular ; the 

 terminal joints of 3rd maxillipeds not concealed by the 4th joint. Calappa 

 Fabr. the carapace with the large crested chelipeds form together a ball- 

 like whole, the postero-lateral margins prolonged over the other trunk- 

 legs. Littoral forms of warm seas. Paracyclois Miers ; Cryptosoma 

 Brulle ; Platymera M. Edw. Orithyia Fabr. the 4 posterior pairs of legs 

 flattened for swimming. 



Fam. 4. Matutidae. Terminal segments of 3rd maxillipeds concealed 

 by 4th segment. Matuta Fabr. 4 posterior pairs of legs flattened, but 

 not setose. They burrow in sand. Hepatus, Latr., Osachila Stimpson, 

 and Actaeomorpha, Miers, have claw-like ends to the legs. 



Fam. 5. Raninidae. Carapace ob-ovate or ovate oblong, the short 

 abdomen partially extended, not folded under the thorax ; 1st antennae 

 not folded in special fossae ; the 4 posterior pairs of trunk-legs with 

 broad terminal joints. Tropical and sub-tropical waters, down to 300 faths. 

 Ranina Lam. carapace broad and truncated in front. Afferent branchial 

 opening at posterior end of thorax. Only 9 pairs of gills. Male copulatory 

 appendages large. East Indies and Pacific Islands. Raninoides M. Edw. 

 last pair of legs filiform ; Notopus de Haan, Lyreidus de Haan. Zanclifer 

 Henderson, with short legs with sickle-shaped end-joints, W. Atlantic 

 coasts. In these two genera the orbits are ill-defined. 



Tribe 3. OXYRHYNCHA. 



Carapace narrowed in front, usually rostrate ; buccal frame quadrate, 

 and epistome large. Central nervous system attains its maximum of 

 concentration. Many of the Oxyrhyncha have serrated and hooked hairs 

 on the upper surface, which serve the purpose of holding fragments of 

 algae, sponges, Alcyonium colonies and other organisms with which they 

 deck themselves, and which grow in this position. They dress in accord- 



