IQI5-] Fauna of the Chilka Lake : Crustacea Decapoda. 309 



Caridina nilotica, sensu lato, is known from an area extending from N. and 

 S. Africa to Celebes. 



Caridina propinqua, de Man. 



1908. Caridina propinqua, de Man, Rec. Ind. Mus., II, p. 227, pi. xix, figs. 6, 6a /. 



1913. Caridina propinqua, Bouvier, Trans. Linn. Soc, Zool. (2), XV, p. 463. 



The specimens of this species from the Chilka Lake agree closely with de Man's 

 description and with individuals from the Gangetic delta. 



According to de Man the species is allied to Caridina fossarum, Heller, and C. 

 laevis, Heller ; but these two forms are widely separated from C. propinqua in the 

 valuable key to certain species of the genus which Bouvier has recently supplied. C. 

 propinqua, in Bouvier' s table, is distinguished from C. laevis, C. fossarum and numer- 

 ous other species by the comparatively greater length of the antennular peduncle. 

 This character is not easily determined with accuracy ; but comparison between C. 

 laevis (of which Javanese specimens are available) and C. propinqua indicates that in 

 these two forms it affords a valid distinction. 



As regards the rostral dentition, in 50 specimens from the Chilka Lake there are 

 from 10 to 17 dorsal teeth (average 136) and of these from 2 to 5 (usually 3) are 

 placed behind the orbit. On the ventral margin there are from o to 3 teeth (average 

 15). In examples from the Gangetic delta the teeth are as a rule rather more 

 numerous. In 50 individuals from Durgapur the dorsal teeth vary in number from 

 9 to 22 (average 167) with from 2 to 5 (usually 4) situated on the carapace behind 

 the orbit. On the ventral margin there are from o to 4 teeth (average i-8). 



There is also a slight difference between specimens from the two localities in the 

 form of the first pair of peraeopods, these limbs being a trifle more slender in the 

 Gangetic form than in that found in the Chilka Lake. The distinction is, however, 

 too trifling to be expressed by means of measurements. 



In both forms the propodus of the last leg is about 2-4 times the length of the 

 dactylus and no differences are to be found in the number of dactylar and uropodial 

 spines and other characters enumerated by de Man. 



The eggs are of the same size as in individuals from the Gangetic delta ; they 

 vary from 051 mm. in length and 032 mm. in breadth when first extruded, to 06 

 mm. in length and 038 mm. in breadth, when on the point of hatching. 



Caridina propinqua occurs in all parts of the main area of the Chilka Lake 

 throughout the year and is especially abundant in thickets of Potamogeton off Cher- 

 ria I., in Barkul Bay and near Nalbano. In the outer channel it was obtained 

 only in the freshwater season (September) and then in no great abundance, specimens 

 being found in Seruanaddi and, in company with C. nilotica, among roots of screw- 

 pines near Arupatna and in submerged grass on the islands near Manikpatna. 



In the main area the species appears to breed throughout the year ; ovigerous 

 females were obtained in the months of January, February, March, July, September 

 and November. A few egg-laden females were also found in September in the outer 

 channel. 



