1895.] 
A. Alcock— Carcinological Fauna of India. 
175 
General form that of an Achseus with the pterygostomian and 
branchial regions so inflated as to push forwards the epistomial region 
to a plane almost at right angles with the antennary region. 
Eyes small, slender, rigidly immovable,—in short undergoing 
degeneration. No orbits or orbital spines. 
Rostrum very short, bifid, at tip, the point of each tooth being 
fused with the distal end of the (otherwise free) sub-cylindrical basal 
joint of the antennary peduncle. Antennae of great length. 
External maxillipeds with the merus rounded and slightly produced 
beyond the articulation — at the antero-internal angle — of the pnlp : 
the merus much narrower than the ischium. Legs long and slender, 
with long filamentous dactyli. Chelipeds short. 
Physachzeus ctenurus, n. sp. Plate III. figs. 2, 2 a-b. 
Carapace sub-triangular, globosely inflated, with all the regions, 
except the cardiac, tumid and fairly well delimited, and with a strong 
post-ocular constriction, beneath which there is an almost vertical 
descent to the mouth. 
The rostrum, which is small, consists of two narrow, slightly diver¬ 
gent, hollow teeth, to either apex of which the distal end of the other¬ 
wise perfectly free basal joint of the corresponding antennary peduncle 
is fused. 
Two large erect procurved spines occur in the middle line of the 
carapace; one on the posterior part of the gastric region, the other 
behind the cardiac region: on either side of the former, but in a plane 
anterior to it, there may sometimes be a spinule. 
In both sexes the abdomen is bluntly but strongly carinated 
down the middle line, the carina in the case of the male ending on the 
6th tergum in a huge recurved spine : in the female instead of a spine 
there is a small tubercle, and the posterior edge of the sixth tergum 
bears a row of four spines. 
The eye-stalks are very small, and are rigidly fixed at right angles 
to the rostrum: the corneas are almost devoid of pigment. There are 
no orbits or orbital spines. 
The antennas are distinctly exposed from their base, and are half as 
long again as the entire carapace, between one-third and two-fifths of 
their extent being formed by the slender peduncle. The basal joint is 
slender and almost cylindrical: it is quite free from neighbouring parts, 
except at the distal end, which is fused with the tip of the rostrum. 
The flagella are fringed with long hairs. 
The antennules are large, and fold longitudinally within the hollow 
teeth of the rostrum. Except in regard of the fingers, the chelipeds 
