Carcinological Fauna of India 175 



General form that of an Acheens with the pterygostomian and 

 branchial regions so inflated as to push forwards the epistomial region 

 to a plane almost at right angles with the antennaiy region. 



P^yes 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 palp : 

 the merus much narrower than the ischium. Legs long and slender, 

 with long filamentous dactyli. Chelipeds short. 



Physachseus ctenums, n. sp. Plate III. figs. 2, 2a-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 month. 



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 pai't 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 

 21 



