REPORT ON THE BRACHYURA. 
213 
Thelphusa, Latreille. 
Thelphusa, Latreille, Nouv. Diet. d. Hist. Nat., ed. 2, vol. xxxiii. p. 500, 1819. 
,, Milne Edwards, Hist. Nat. Crust., vol. ii. p. 10, 1837 ; Ann. d. Sci. Nat., ser. 3, Zool. 
xx. p. 209, 1853. 
„ A. Milne Edwards, Nouv. Archiv. Mus. Hist. Nat., vol. v. p. 163, 1869, et 
synonyma. 
„ Kingsley, Proc. Acad. Nat Sci. Philad., p. 35, 1880. 
Carapace transverse, with the anterolateral margins arcuated and usually armed 
with a single tooth, placed at a short distance behind the tooth or lobe at the exterior 
angle of the orbit, sometimes moderately convex, with a more or less distinct post-frontal 
crest, sometimes very convex, and the post-frontal crest obsolete. Front deflexed, of 
moderate width. Orbits usually without marginal fissures, and with the interior sub- 
ocular lobe but little developed. Epistoma narrow, transverse. Endostome not longi- 
tudinally ridged. Post-abdomen (in the male) usually distinctly seven-jointed. Eyes of 
moderate size. Antennules transversely plicated and usually almost concealed beneath 
the front. The basal joint of the antennae is very short, and does not always reach the 
frontal margin ; the short flagellum lies within the anterior hiatus of the orbit. The 
ischium-joint of the exterior maxilli pedes is not produced at its antero- internal angle ; 
the merus is small, usually distally truncated, with the antero-external angle rounded, 
the antero-internal angle (at or near which the next joint articulates with the merus) 
slightly emarginate. The chelipedes (in the males) are well developed and usually 
unequal, with the merus trigonous ; carpus with a strong spine on its inner margin, 
palm rounded above ; fingers usually not so long as the palm, distally acute, and dentated 
on the inner margins. The ambulatory legs are rather long, with styliform dactyli, 
which are armed with spinules disposed in longitudinal series. 
The described species of Thelphusa are very numerous ; one, the common Thelphusa 
fluviatilis, occurs not only on the shores of the Mediterranean, but also in Asia Minor, 
Syria and Persia ; the others are found in all the warmer temperate and tropical regions 
of the Old World, extending southward to the Cape of Good Hope, Madagascar and 
Australia, but not to New Zealand ; a species ( Thelphusa chilensis) occurs in Chili. 
The genus may be divided into three sections or subgenera, characterised mainly by 
the form, (when developed) of the postfrontal crest ; the Challenger collection includes a 
species belonging to each of these sections, which are connected with one another by 
insensible gradations. 
I. Carapace moderately convex, but little dilated in front of the branchial regions, 
with the epibranchial tooth usually distinctly developed. Postfrontal crest distinct, but 
not continuous. Typical Thelphusse. 
The species are mostly Mediterranean and Asiatic. 
II. Carapace moderately convex, usually antero-laterally dilated, with sometimes one 
