IÇI5-J Fauna of the Chilka Lake ; Crustacea Decapoda. 321 



Penaeopsis monoceros (Fabricius). 



1906. Metapeneus monoceros, Alcock, Cat. Indian Decaf. Crust., Ill, i, p. 18, pi. iii, figs. 7, ja-c. 

 1911. Penaeopsis monoceros, de Man, Decap. 'Siboga' Exped., I, Penaeidae, p. 55, and (1913) 

 pi. vi, figs. 14a, c. 



The small tooth at the distal extremity of the ischium of the first peraeopods, 

 mentioned by de Man (loc. cit., p. 56) is present in Indian examples of this species. 



P. monoceros is very abundant in the Chilka I,ake and is brought into the local 

 markets in large numbers. It occurs both in the main area and in the outer channel 

 at all seasons of the year. 



In life specimens are semitransparent, closely covered with small red chromato- 

 phores. The dorsal carina of the carapace, the rostrum, the bases of the eyestalks, 

 the dorsal abdominal carinae and the carinae of the telson and uropods are defined 

 by dull red pigmentation. The antennae are bright red, the first two legs colourless, 

 the last three with numerous red chromatophores. The setae that fringe the uropods 

 are golden red and the outer uropod is bright red along its external margin. The 

 nerve-cord is sheathed in red pigment and is clearly visible from beneath. 



The species is known from an area extending from the Indus delta to Hongkong 

 and Japan and perhaps also occurs in Australia. 



Penaeopsis af finis (A. Milne-Edwards). 



1906. Metapeneus affinis, Alcock, Cat. Indian Decap. Crust., Ill, i, p. 20. 



1911. Penaeopsis affinis, de Man, Decap. 'Siboga' Exped., I, Penaeidae, p. 57, and (1913) pi. vi, 

 figs. 15a, b. 



At the time of their capture specimens of this species were not distinguished 

 from P. monoceros. In the collection are some twenty individuals, the largest, about 

 105 mm. in length, obtained in February and March at various localities in the main 

 area between Rambha and Kalidai I. P. affinis is recorded by Alcock from ' Investi- 

 gator ' dredgings on the Orissa Coast ; it therefore doubtless occurs in the outer chan- 

 nel and it is probable that, like P. monoceros and P. dobsoni, it is to be found in the 

 lake at all seasons of the year. 



The species is known to be distributed over an area extending from the Indus 

 delta to Japan. 



Penaeopsis dobsoni (Miers). 



1906. Metapeneus dobsoni, Alcock, Cat. Indian Decap. Crust., Ill, i, p. 21, pi. iii, figs. 9, ga-d. 

 1911. Penaeopsis sp., de Man, Decap. 'Siboga' Exped., I, Penaeidae, p. 60 and (1913) pi. vi, 

 fig. 17. 



With respect to this species Alcock notes that in the vast majority of the females 

 that he examined the fifth legs are reduced to a pair of horn-capped stumps. P. dob- 

 soni is very abundant in the Chilka Lake, but in every female obtained the last legs 

 are of normal length. It appears to me highly probable, as has already been sug- 

 gested by Nobili, that the degeneration of these limbs is in some way connected with 

 reproduction and, if this should prove to be the case, the condition of the Chilka 



