488 



Records of the Indian Museum. 



[Voi,. XXIV, 



miles from the sea, were taken at a point much further inland than 



any previously recorded." (N. A.). 



R. marks. — Zimmer in his revision of the Mysini was unable 



to place this species and genus because he was of opinion that 

 the male from which I figured the fourth pleo- 

 pod was not mature. I find that this opinion 

 is correct. Among the present specimens are 

 two or three fully grown males, somewhat lar- 

 ger than I have examined before, and I find 

 that the drawing I gave of the fourth pleopod 

 of the male requires modification. The outer 

 branch is five-jointed not three-jointed as I 

 have described it, the third joint of my pre- 

 vious figure being subdivided into two- extra 

 small joints at the distal end. Each of these 

 last three joints bears a single plumose seta at 

 its outer distal end, those on the terminal and 

 penultimate joints about equal in size, while that 

 on the antepenultimate joint is much longer 

 and stouter, and is plumose and not smooth as 

 I had previously described it. Immature speci- 

 mens have the fourth pleopod as I had previ- 

 ously described it, that is with the two small 

 terminal joints of the outer branch not marked 

 off and the large seta on the third joint smooth 

 and not plumose. 



The fourth pleopod in this species is remark- 

 ably like that of the genus Stilomysis, but the 

 third pleopod of the latter is two branched 

 whereas in P. assimilis it is rudimentary as in 

 the female. 



It is now possible to put this genus in its place 

 in Zimmer's key. It should be placed in Group 

 III B in which it will form a separate section, 

 characterised by the large number of joints in 



the outer branch of the fourth pleopod of the male. 



Text-fig 22. — 



Potamomysis 



assimilis, 



Tattersall. 



Fourth pleopod 

 of the adult male, 

 X 65. 



Genus Idiomysis, nov. 



Body robust and gibbous, in the only specimen, flexed in the 

 curious way shown in text-fig. 23a. Carapace produced in front 

 into a large frontal plate with a broadly rounded apex. Eyes 

 very large, stalks short, pigment golden brown. Antennular 

 peduncle with the male lobe well developed and densely hirsute. 

 Antennal scale very short and broad, the greater part of the 

 outer margin smooth, without setae, no transverse suture distally. 

 Second maxilla with the outer plate very reduced, with only four 

 or five setae. First thoracic limbs with a masticatory lobe on the 

 second joint only. Tarsus of the third fourth, sixth, seventh and 

 eighth thoracic limbs unjointed. Fifth thoracic limbs markedly 



