216 
THE VOYAGE OF H.M.S. CHALLENGER. 
Scarcely any indications of a postfrontal crest exist in this species, but the proto- 
gastric prominences are obscurely developed. Ordinarily there is no lateral epibranchial 
tooth, the antero-lateral margins of the carapace being simply granulated, but occasion- 
ally, as in the specimen collected near Lake Biwa, it is distinctly defined. This, the 
largest specimen, has the following dimensions : — 
Adult . Lines. Millims. 
Length of carapace, about . . . . . . 9| 20-5 
Breadth of carapace, . . . . . . 12 25 - 5 
CATOMETOPA or OCYPODIIDEA. 
Quadrilatera, Latreille (pt.), Fam. Nat. du Regne Anim., p. 269, 1825. 
Catometopes, Milne Edwards (pt.), Hist. Nat. Crust, vol. i. p. 264, vol. ii. p. 1, 
1834-37. 
Ocypodidse. Milne Edwards (pt.) Ann. d. Sci. Nat., ser. 3, Zool. xviii. p. 140, 
1852. 
Grapsoidea, Dana, U.S. Explor. Exped., vol. xiii., Crust., pp. 67, 306, 1852. 
Catometopa, Miers, Cat. New Zeal. Crust., p. 32, 1876. 
Carapace broad in front, often subquadrate, sometimes subglobose, truncated or 
arcuated anteriorly, but not rostrated. Epistoma short, often almost linear. Afferent 
branchial channel as in the Oxyrhyncha. The carpal joint of the exterior maxillipedes 
inserted at the summit, or more usually at the antero-external angle of the merus, very 
rarely at its antero -internal angle. Branchiae usually fewer than nine in number. The 
male verges are inserted either in the sternum itself or in the basal joints of the last pair 
of legs, thence passing through channels in the sternum beneath the post- abdomen. 
Family I. Geocarcinida 
Gecarciniens, Milne Edwards, Hist. Nat. Crust., vol. ii. p. 16, 1834. 
Gecarcinacea, Milne Edwards (pt.), Ann. d. Sci. Nat., vol. xviii. p. 200, 1852. 
Gecarcinidaz, Dana, U.S. Explor. Exped., vol. xiii., Crust. 1, p. 374, 1852. 
Carapace dorsally very convex, and especially dilated over and in front of the 
branchial regions, with the antero-lateral margins usually entire and very strongly 
arcuated ; the front of moderate width and strongly deflexed. Orbits and eye-peduncles 
of moderate size. The post-abdomen of the male usually covers at the base the whole width 
of the sternum, between the bases of the ambulatory legs. The carpal joint of the exterior 
