250 



Records of the Indian Museum. [Voi, XXIV, 



is a little longer than the merus and nearly twice as long as 

 the chela ; the fingers are much shorter than the palm. The 

 structure of the chela, as Tattersall has pointed out, is very 

 peculiar. 1 The edge, both on its outer and inner side, is pro- 

 duced to form a sort of flap which is bent downwards and is 

 thickly fringed with long setae on its margin. The chela is thus 

 deeply hollowed in a longitudinal direction when viewed from 

 below and in a transverse section the lower surface would be 

 semicircular (see Tattersall, loc. cit., fig. 4). 



The second peraeopods are unequal, either the right or left 

 limb may be enlarged. In the larger of the two the merus is 

 from 2*0 to 2*4 times as long as broad ; the carpus is very short, 

 only one-sixth to one-eighth the length of the chela and the fingers 

 are a little more than half the length of the palm. The dactylus 



Text-fig. 81. — A?ichistus insri.iis (Miers). 



a. Antennal scale. c. Dactylus of third peraeopod. 



b. Third maxilliped. d. Telson. 



is strongly convex externally. On the inner margin it bears in 

 its basal half a very large triangular tooth and a rounded knob 

 close to the articulation ; when the claw is closed both the tooth 

 and the knob are received into a large socket in the fixed finger. 

 The inner margin of the fixed finger is obtusely produced in the 

 middle and in the basal half, on a crest which borders the socket 

 on its upper side, there are usually from 3 to 6 small denticles, the 

 foremost placed at the summit of the obtuse prominence referred 

 to above. In all well-developed specimens the distal half of each 

 finger is internally concave. The fingers of the smaller limb are 

 similar, but the tooth on the dactylus is usually less well developed. 

 In the last three peraeopods the propodus is without spinules 

 on its posterior edge. The dactylus (text-fig. 81c) is strongly 

 hooked, with the terminal claw bent at right angles to the proxi- 



1 The character is not sexual as suggested by Tattersall. 



