XXV. THE FAUNA OF BRACKISH PONDS 

 AT PORT CANNING, LOWER BENGAL. 



Part XI. — Two new Mysid^ from Brackish Water 

 IN THE Ganges DeivTa. 



By WAI.TER M. Tattersai.1., M.Sc. 



I am indebted to the courtesy of Dr. J. G. de Man, to whom 

 I wish to express my thanks, for the opportunity of examining and 

 describing the two species of Mysidse which form the subject of 

 the present note. The material was collected in brackish water 

 ponds near Calcutta by Dr. Nelson Annandale, who is making an 

 exhaustive study of the lacustrine fauna of Bengal. The majority 

 of the specimens belong to the interesting genus Macropsis, but 

 appear to differ in some points from the widely distributed and 

 hitherto only known species, M. slabberi, sufficiently to warrant 

 the establishment of a second species of that genus. The second 

 new form here described is represented by only nine specimens. 

 It belongs to the little known and somewhat obscure genus 

 Potamomysis , but after much hesitation, I have decided to insti- 

 tute a new species for its reception. 



Sub-fam. MYSIN^. 



Genus Potamomysis, Czerniavsky, 



Potamomysis, Czerniavsky, Monog. Mysid. Imperii Rossici, fasc. 

 i, p. 129, 1882; fasc. iii, p. 78, 1883. 



This genus was described by Czerniavsky in the monograph 

 referred to above, and has not since, so far as I am aware, been 

 met with. The type of the genus with its single species, P. pengoi, 

 was a female, and I cannot gather from the text that Czerniavskj^ 

 ever examined male specimens. Yet in the two keys to the genera 

 of Mysidse which he gives on pages 57 and 62 of the first part of 

 his monograph, he places Potamomysis in that group of genera 

 characterised by having the first, second and fifth pleopods of the 

 male rudimentary as in the female, the third and fourth pairs 

 somewhat dissimilar from those of the female, but not truly 

 natatory. 



If I am right in referring the present species to Potamomysis^ 

 the position assigned to this genus in Czerniavsky's keys is incorrect, 

 since the third, as well as the first, second and fifth pleopods of 



