Crustacea Decapoda and Stomatopoda. 255 



the variation in the number of spinules on the legs is thus rather greater than was 

 gathered from examination of the Indian specimens. 



The species has hitherto been found only in the Chilka Lake on the Orissa coast 

 of India, where it was obtained in water ranging in specific gravity from i-ooo to 

 1-0265. 



DECAPODA NATANTIA. 



Tribe CARIDEA. 



Family PALAEMONIDAE. 



Genus Palaemon, Fabricius. 



Palaemon carcinus, Fabricius. 



1890. Palaemon carcinus, Ortmanii, Zool. Jahrb., Syst., V, p. 700, pi. xlvii, fig. i. 



1902. Palaemon {Eupalaemon) carcinus, de Man, Ahhandl. Senck. naturf. Ges., XXV, p. 763. 



1910. Palaemon carcinus, Henderson and Matthai, Rec. Ind. Mus., V, p. 281, pi. xv, figs, i a-g. 



1914. Palaemon carcinus, Cowles, Philippine Joiirn. Soi., Sect. D, IX, p. 324, pi. i, figs, i, 



1(7-/. 



The collection contains numerous specimens of this well-known species from 

 the Malay Peninsula. Three males, which doubtless came from the Patalung river 

 where the water is always fresh, were bought in the market at Lampam and a large 

 number of specimens were obtained from fishermen's nets at Singgora in the Tale 

 Sap in water of specific gravity varying from 1-004 to 1-0085. 



■ It is a remarkable fact that all the Singgora specimens, with one exception, are 

 females and that nearly all of them bear eggs. In our investigations on the fauna 

 of the Chilka Lake on the Orissa coast of India, we drew attention to the fact that 

 certain species of Palaemon, P. yudis and P. malcolmsoni , visit the lake each year at 

 the period when its waters are at their freshest in order to liberate their young. In 

 the case of P. malcolmsoni this migration is undertaken only by the ovigerous females, 

 whereas in P. rudis the males accompany the females.^ 



It appears that a similar phenomenon occurs in the Tale Sap in the case of 

 P. carcinus. Dr. Annandale found only a single male and very few females without 

 eggs out of many hundreds of specimens examined at Singgora and there can be 

 little doubt that the females migrate to the lake for breeding purposes. The speci- 

 mens were obtained in January at the beginning of the dry season when the water of 

 the outer part of the lake was probably fresher than at other times. 



The specimens agree well with the published descriptions. The rostrum as a 

 rule extends much beyond the antennal scale, but in one male from Lampam, 

 168 mm. in total length, reaches beyond this point only by some 5 mm. There are 

 from 12 to 15 teeth on the upper border of the rostrum and from 10 to 14 (usually 

 12 to 14) on the lower border. Nine specimens yield the following measurements 

 (to the nearest mm.) : — 



1 Kemp, Mem. Ind. Mus., V, p. 203 (191 5). 



