I9I5-] 



Fauna of the Chilka Lake : Mysidacea. 



157 



spine in G. muticus and bears at its base a similar shorter curved spine as in the latter 

 species. The inner margin of the fifth joint bears two long obtusely-pointed and 

 microscopically-ridged processes , but there are no signs of the prominent stout spines 

 with the bifurcated tip so characteristic of G. muticus. 



The length of adult male and females is 7-8 mm. 



The following text-figures , showing the exopods of the third pleopod of the males 

 of G. spinifer, G. muticus and G. simulans, will illustrate the fundamental differences 

 in these organs in the three species and indicate the main characters on which the 

 three forms are to be separated : — 



Os. 



Text-fig. r. — Exopod of third pleopod of male in three species of Gastrosaccus. 

 a. G. spinifer, Goes ( x 25). b. G. muticus, n. sp. ( x 60) Form A. c G. simulans, n. sp. ( x 60). 



d. G. muticus, n. sp. ( x 90) Form B. 



I provisionally refer to this species, the specimens from the following locality :— 



Estuary of the river Bassein, Burma, coll. Marine Survey of India, two adult 

 females, 7 mm. 



There are no adult males or immature specimens from the same locality, but these 

 two females agree absolutely with the adult females of G. simulans, and I cannot see 

 any reason for separating them at present. 



The discovery of these two new species of Gastrosaccus illustrates, still further, 

 the difficulty which exists in accurately discriminating the various species of the 



