CEYLON ALPHEID &. 169 
CEYLON CRUSTACEA. 
Part 1.—Notes on the Alpheidez. | 
By JosEpH PEARSON. 
(With three Plates. ) \ OY. % BH 
SL 
| present report deals with a small collection of Alpheids 
from the Colombo Museum. The members of the genera 
Alpheus and Synalpheus, though numerous in individuals and 
species, are but little known to any but the specialist in marine 
carcinology. This is partly owing to their small size, but mainly 
due to the fact that they generally take up their abode in the deep 
recesses of some sponge or in the crevices of a fleshy alcyonarian, 
and even, for want of more favourable shelter, in some friendly 
hole in a coral. Thus the casual collector may be in the midst of 
a rich Alpheid fauna without being aware of the fact. Often, how- 
ever, when sponges are brought up in the dredge and are emptied 
on deck, the Alpheids will emerge from their retreat. 
These tiny creatures are characterized by having an asymmetrical 
pair of chele, one of them being extremely large, perhaps half as 
big as the body of the animal, while the other is of normal size. 
The large chela does not appear to be restricted to one side of the 
body in any particular species. It may be either on the left or on 
the right side. It is hard to say along what lines this single large 
chela has been evolved, and the exact meaning of its abnormal 
development. The Alpheids live in holes, and it is conceivable 
that, like the hermit crab, the single large claw may be used to block 
the entrance to the shrimp’s retreat. But this does not afford a 
satisfactory explanation, especially in view of the fact that an 
Alpheid is much more independent of its place of shelter than is the 
hermit crab. Moreover, many active Macrurans, such as some of 
the Palemonide, often have asymmetrical chele. 
These small crustaceans are sometimes known as “snapping 
shrimps,” on account of an interesting habit they have of snapping 
the fingers of their huge claw. When emptied on deck out of 
the dredge, or when put into a dish of water, they frequently betray 
their presence in this way, making a noise which may readily be 
heard at a distance of fifteen or twenty feet. 
I give here an interesting note on the habit of Alpheids, contri- 
buted-by my assistant, Mr. George Henry. He says :— 
“On one occasion I watched two Alpheids, male and female, 
courting. They were in a pie-dish, full of sea water, with several 
other* creatures, among which were some other Alpheids. The 
Zz 6(11)11 
