REPORT ON THE BRACHYURA. 
217 
maxillipecles is sometimes inserted at the antero-external angle of the merus, sometimes 
at the apex or near its antero-internal angle, and may be completely concealed 
beneath the merus. The chelipedes in the adult male are very robust and usually 
unequally developed. The dactyli of the ambulatory legs are nearly always granulated 
and armed with spines disposed in longitudinal series. 1 
Geocarcinus, Leach. 
Geocarcinus, Leach, Trans. Linn. Soc. Loud., vol. xi. p. 322, 1815. 
„ Milne Edwards, Hist. Nat. Crust., vol. ii. p. 26, 1837 ; Ann. d. Sci. Nat., ser. 3, 
Zool. xx. p. 201, 1853. 
Carapace transverse and anteriorly convex, with the mesogastric and cervical 
sutures strongly defined, and the branchial regions antero-laterally convex and greatly 
developed ; the antero -lateral margins not distinctly dentated. The front is deflexed 
and narrow or of moderate width, anteriorly truncated, nearly reaches the anterior 
margin of the buccal cavity, and almost completely covers the antennules. Orbits of 
moderate size, with the superior margins subentire, no distinct tooth at the exterior 
angle, and with a well-marked hiatus in the inferior margin, near the interior sub- 
ocular lobe, which is in contact with the front, and excludes the short antennae from the 
orbit. No distinct ridges are developed upon the endostome or palate. The post- 
abdomen in the male is usually distinctly seven-jointed. The eyes are set on rather 
short, thick pedicels. The antennte are very short and occupy the angle formed by the 
contact of the inner subocular lobe of the orbit with the front, their basal joint is 
slightly dilated and does not reach the frontal margin. The exterior maxillipedes 
bulge out externally, and enclose a lozenge-shaped interspace ; ischium and merus are 
broad, the ischium not produced at the antero-internal angle, merus clistally rounded 
and prolonged so as almost entirely to conceal the following joints, it has sometimes a 
fissure in the antero -lateral margin ; the following joint is articulated with the merus on 
its inner surface. The chelipedes (in the adult male) are considerably developed and 
usually unequal ; merus trigonous and somewhat elongated ; carpus without a spine on 
the interior margin ; palm rounded above ; fingers distally acute and dentated on the 
inner margins. The ambulatory legs are robust and somewhat elongated, with the 
penultimate and terminal joints, and sometimes the antepenultimate joint, compressed, 
and armed with spinules disposed in longitudinal series. 
The species included in this genus are not numerous and inhabit, for the most part, the 
West Indian Islands, Brazil, Central America and California. One species, Geocarcinus 
lagostoma , has apparently a very extensive range, i.e., from Australasia (1) to the Cape 
1 In Uca they are compressed and unarmed. 
(zool. chall. EXP. — PART XLIX. — 1886.) 
Ccc 28 
