CEYLON. ALPHEID2. Lr 
Six specimens, from Weligama. 
Three specimens, from the Pearl Banks ; February, 1911. 
According to Coutiére this is the commonest species of Alpheus, 
and the most widely distributed. 
I have followed Coutiére in including Randall’s species along with 
that of Milne-Edwards. 
This is one of the few examples of an Alpheus possessing orbital 
spines. 
The rostrum, which extends almost to the extremity of the first 
antennular article, is well developed, and is separated from the orbits 
by well-defined grooves. 
The first and second antennular articles are almost equal and 
nearly twice as long as the distal article. The antennular scale 
reaches nearly to the middle of the second article. 
The antennal peduncle and scale are about equal in length, and 
extend beyond the antennular peduncle by a distance nearly equal to 
the third antennular article. There is a basal scale present which is 
nearly as long as the first antennular article. 
This species is characterized by having the cephalothorax laterally 
compressed to a marked degree. The carapace is very deep, and 
its greatest depth is equal to its mid-dorsal length. Instead of the 
lower edge of the carapace being rounded as in most species, there 
are several sharp angles which give this form a very characteristic 
appearance. 
The following are the dimensions of a typical specimen :— 
ar — 9 Ojmimn: | b4 = 3°5 mm. ; @ ==14-°9 mm. 
b1 = 1:7 mm. — bd) = 2:8 mm. | el = 6:0 mm. 
b2 = 4°25 mm. bf = 3-0 mm. | ve4==455 emo, 
6? = 3:6 mm. | 6? = 5-0 mm. 
The large claw is laterally compressed, and possesses no upper and 
lower teeth on the palm. The hands of both the first pereiopods are 
coloured bright orange in the living specimen and have a mottled 
appearance. Some of the specimens have a setiferous ridge on the 
movable finger of the smaller hand. The presence of this setiferous 
ridge is doubtless a sexual difference, and is probably confined to 
males. I cannot, however, give any proof of this, as in every 
specimen the first pereiopods are detached and are lying loose at the 
bottom of the bottle. 
The second pereiopod is not so slender as in most Alpheids. The 
hand is richly clothed with sete. 
The following are the measurements of the second pereiopod :— 
t = 2112; 825 | c? = 10238; 759 6 sesh2ZE 693 
m = 4290; 990 c? = 858 ; 726 _ p = 1551; 693 
G) 262310 5792, |. c* == 8255 726 lis dd. =="359% 297 
2a 6(11)11 
