1921.] Fauna of the Chilka Lake : Amphipoda. 525 



second gnathopod overlaps the palm and Chevreux, who was able to examine a large 

 number of specimens, found this to be the case in all his specimens of A . neapolitanus, 

 even those only 1 mm. long, while in A . brunneus it varied between the half and two- 

 thirds and did not overlap the palm. Hence I refer the Chilka I^ake specimens to A . 

 brunneus, for in none of them does the process overlap the palm. Walker's speci- 

 men from Ceylon doubtfully referred to A . neapolitanus is probably the same. 



[This species was habitually taken on the subumbrella and among the tentacles 

 of the only large medusa found in the lake, Acromitus rabanchatu, Annandale. The 

 amphipods were almost invariably present in this situation in adult medusae. N.A ,] 



Idunella chilkensis sp. nov. 



(Text-fig. 1). 

 Localities : — 



1 mile E. by N. of Patsahanipur. Five males, one female. 



2-6 miles E. by S. \ S. of Patsahanipur. One male, one female. 



Specific Diagnosis. 



Male. Pleon segments 2, 4 and 5 produced into minute dorsal teeth. Rostrum 

 short or absent. First side plate large, broadly rounded in front, side plates 1 to 3 

 with minute denticle at lower hind corner. Postero-lateral angle of third pleon 

 segment acute, a small sinus between the point and the convex hind margin. 



Antenna 1 (fig. la) about three-fourths as long as the body, stout; first joint 

 of peduncle about as long as the second but much stouter, third joint very short, not 

 longer than first joint of flagellum ; flagellum stout, consisting of about 35 joints, 

 accessory flagellum small, of two slender joints. 



Antenna 2 (fig. la) shorter than the first antenna, ultimate and penultimate 

 joints of peduncle subequal, flagellum stout, about as long as peduncle. 



Mouth parts closely resembling those of /. aequicornis. 



First gnathopod (fig. id) large, basis slender, with two or three long setules 

 near base of hind margin and a large group about the middle of anterior margin : 

 ischium and merus short, subequal, two long setules at distal angle of merus; carpus 

 very short, triangular, propod very large, longer than the rest of the limb, broadly 

 oval, anterior margin regularly convex and without setae, palm very oblique, 

 irregularly defined by 3 or 4 stout setules, having near the finger a prominent lobe 

 ending in two or more blunt teeth, a depression near the lobe followed by a convex 

 serrated and setulate portion leading to the defining setules; hind margin much 

 shorter than palm, convex, fringed with minute setules ; finger long and strongly 

 curved, having a concavity near the base followed by a slight prominence, inner 

 concave margin slightly irregular. 



Second gnathopod much smaller, carpus produced near the antero-distal angle ; 

 propod oval, longer and broader than carpus, anterior margin convex, bearing tufts 

 of slender setules ; palm not very oblique, convex, with minute setules ; hind margin 

 longer than palm, with 4 or 5 tufts of setules ; finger strongly curved, fitting closely 

 on to the palm. 



