546 CRUSTACEA MALACOSTRACA. 



Arctopis, Lam. (Pisa, Leach) cephalo thorax elongated pear-shaped with 

 preorbital spine and long rostrum, basal joint of 2nd antenna narrow and 

 inserted besides the rostrum ; two spp. British. Lissa Leach. Chionoe 

 cetes Kroy. Greenland and New England, spans 32 inches. Antilibinia 

 MacL. A. Smithii M'Leay, has powerful claws with which it clings to 

 wave-beaten rocks. Natal. Scyramathia M. Edw. Eurynome Leach, 

 cephalothorax irregularly rhomboid. E. aspera (Perm.) Mediterranean, 

 extending to Britain. 



Fam. 3. Periceridae. Eyes retractile within complete orbits. Pericera 

 Latr., Macrocoeloma Miers, Libinia Leach. Mithrax Latr. 



II. Basal antennal segment very small, the orbit having an inferior 

 wall distinct from it. 



Fam. 4. Parthenopidae. Chelipeds very long. Parenthope Fabr. 

 P. horrida (L.) the great warty crab of the E. and W. Indies ; Lambrus 

 Leach, cephalo-thorax triangular ; widely distributed in the shallow water 

 of warm seas ; Heterocrypta Stimpson. 



With the Oxyrhyncha is probably allied Paratymolus Miers, from 

 Australia. 



Tribe 4. CATOMETOPA. 



Carapace broad anteriorly, not rostrate, the front * bent downwards, 

 epistome short. 



Fam. 1. Grapsidae. Carapace more or less quadrilateral ; front 

 generally very broad ; mostly littoral or shallow water forms. Grapsus 

 Lam. Carapace with transverse ridges ; some species frequent exposed 

 rocks, running with great agility. Nautilograpsus M. Edw. N. minutus ( L. ) 

 widely distributed and abundant in the Gulf -weed of the N. Atlantic. 

 Like other members of the Gulf-weed fauna it is mottled with yellow, 

 brown and white in varying patterns, resembling the young and old 

 branches of the weed, with the white encrusting Polyzoan colonies which 

 grow on it. Several members of this, as of the two succeeding families, 

 have adopted a semi-terrestrial mode of life. Eriocheir de Haan ; E. 

 japonicus de Haan, with furry chelae, ascends fresh-water streams in 

 Japan, and lives partly on land. Sesarma Say, widely distributed in 

 warm, shallow waters. S. pisonii climbs mangrove bushes, taking air 

 into its branchial cavity by openings at the back of the thorax. Another 

 species inhabits marshy ground and has a sieve-like arrangement of 

 hairs on the pterygostomial region for re-aerating the water driven from 

 the branchial cavity, and conducting it to the afferent opening in front 

 of the bases of the chelipeds. It is also able to take in air at the back of 

 the thorax (Fr. Miiller). Several other genera. 



Fam. 2. Ocypodidae. Carapace moderately convex, sometimes 

 trapezoidal ; front of moderate width or very narrow. Eye-stalks may 

 be greatly developed ; terminal joints of walking legs styliform, without 

 strong spines. Littoral to considerable depths. Ocypode Fabr. front 

 narrow, orbits and eye-stalks very large, the latter often prolonged beyond 

 the (lateral) corneal surface. Chelae unequal in male, the larger one very 

 mobile, the 6th joint (" hand ") bearing a regularly striated band which 

 plays over a ridge on the third joint, forming a stridulating apparatus. 



* The " front " is the region of the upper surface of the carapace between 

 the orbits. 



