CRUSTACEA OF THE MERGUI ARCHIPELAGO. 2638 
flattened, especially on its distal half, and is bordered by two 
longitudinal and parallel crests, of which the external one, how- 
ever, scarcely extends proximally beyond the oblique impressed 
line at the base of the outer surface of the hand, whereas the 
internal crest is a little longer. Immediately before the articu- 
lation of the mobile finger, a small transverse groove occurs on 
the upper surface of the palm, as in Alpheus malabaricus (Fabr.), 
de Haan. The under, like the upper, margin of the palm is flat- 
tened; so that an under surface may be spoken of. As already 
observed, the inner margin of this under surface is bordered with 
rather long hairs. The mobile finger is strongly compressed 
laterally, and is broad and bluntly rounded at its distal extremity ; 
the elevated proximal half of the inner margin of the immobile 
finger is fringed with rather long hairs on the inner side of the 
hand, and the outer and inner surfaces of the fingers are algo a 
little hairy. 
The other leg measures 39 millim., is much shorter than the 
former, and scarcely twice as long as the carapace. The hand 
of this smaller chelipede is 223 millim. long, the palm measuring 
83 millim., so that the fingers are only once and a half as long 
as the palm. The palm is compressed and fringed with long 
hairs along the upper and under margins of its inner surface; 
the fingers are slightly arcuated and present a space between 
their inner margins, which are densely clothed with rather long 
hairs, and the tips cross when closed. 
The joints of the carpus of the second pair of legs are respec- 
tively 44, 32, 14, 14, and 12 millim. long; the first or proximal 
joint is therefore the longest of all, and even a little longer than 
the second, and the latter is nearly as long as the three distal 
joints together. 
The younger specimen, which is only 34 millim. long from the 
tip of the rostrum to the end of the terminal segment of the 
abdomen, presents only two slight differences from the adult 
worthy of notice. The rostrum, as in the adult Alpheus rapax 
(Fabr.), de Haan, extends backwards nearly to the middle 
of the carapace, and the antennal scales scarcely project beyond 
the peduncles of the internal antenne. This specimen in other 
respects perfectly resembles the adult. 
This species is closely allied to the Japanese Alpheus malaba- 
ricus (Fabr.), de Haan, and A. Kingsleyi, Miers. It differs at 
