410 
APPENDIX. 
culars. Madagascar appears to be the tropical confines of 
the genus. 
2. The Western Australia Cray-fish. Astacus quinque-cari- 
natus, t. 3. f. 3. — Carapace smooth, rather convex, andwith 
three keels above ; the beak, longly produced, ending in a 
spine, simple on the side and produced into a keel on each 
side behind ; the central caudal lobe rather narrow, indis- 
tinctly divided in half, and like the other lobes flexile at 
the end, the lateral lobes with a central keel ending a 
slight spine ; the hands elongated, compressed, smooth, 
with a thickened, toothed, inner margin, which is ciliated 
above ; wrist with two conical spines on the inner side. 
Inhab. Western Australia, near Swan River. 
3. The Port Essington Cray-fish. Astacus bicarinatus, 
t. 3. f. 2. — Carapace smooth, rather flattened, with a keel on 
each side above in front; the beak longly produced, flattened, 
three toothed at the top ; hands rather compressed, smooth, 
thinner and slightly toothed on the inner edge ; the wrist 
triangular, angularly produced in front ; the central caudal 
lobes with two slightly diverging keels continued, and like 
the others thin and flexible at the end, the inner lateral 
lobes with two keels, each ending with a spine. 
Inhab. Port Essington, Mr. Gilbert. 
The A. Australasiensis, Milne Edwards, Crust ii. 332. t. 
24. f. 1 — 5. agrees with this species in the form of the beak, 
but the keels on the thorax are not noticed either in the 
description or in the figure ; and the caudal lobes in the 
figure appear most to resemble A. Franklinii. 
As the genus Astacus is now becoming more numerous in 
species, it may be divided, with advantage, into three sec- 
tions, according to the form of the caudal lobes ; thus : — 
A. The central caudal lobes divided by a transverse suture 
into two parts, both being hard and calcareous, and with a 
small spine at the outer angle of the suture (Patamobius, 
