540 Memoirs of the Indian Museum. [Vol. V, 



conclusion, I looked up Stebbing's report on the Amphipoda in the Fauna Hawaii- 

 ensis, and found that the specimens he had referred to 0. pickeringii were taken 

 at the same locality, on the same date, and at the same height as specimens he 

 referred to 0. platensis. He separates these two sets of specimens because of 

 certain points in the number of joints in the second antennae, etc., but I doubt 

 if these are sufficient to be of specific importance. Apparently he had no male 

 specimens of 0. platensis fully mature and he draws the palm of the second 

 gnathopod evenly convex as it is in most of the Chilka Lake specimens. In his 

 figure too he shows the second antenna more slender than in some of the Chilka 

 Lake specimens, and this again probably indicates that the figure was taken 

 from a male not fully developed and suggests the probability that the specimens 

 he referred to 0. pickeringii were only more developed examples of the same 

 species. 



I have been able to compare the Cold Spring Harbor specimens (0. agilis) with 

 a specimen of 0. incisimana Chevreux from the Mediterranean and agree with 

 Stebbing that both of these should rightly be referred to 0. platensis. In the Cold 

 Spring Harbor specimens the carpus of the fifth peraeopod is slightly broadened, 

 while in the Mediterranean specimens (0. incisimana) it is considerably broader. 

 Apparently no one of the Cold Spring Harbor specimens that I have examined is 

 quite fully developed, for Kunkel states that the merus and carpus of the fifth 

 peraeopod in the adult male are greatly swollen. Stebbing, however, says of 

 0. platensis " 5 th joint of peraeopod s 4 and 5 also thick but without great widening," 

 and these joints are not broadened in any of the Chilka Lake specimens. It is 

 probable, therefore, that the broadening of these joints occurs only in very old 

 males and that the animals may reach sexual maturity without any broadening, just 

 as happens in 0. tueur auna F. Müller and other species. 



Chevreux (1908, p. 494) records 0. platensis Kröyer from the Marutea du Sud 

 and Taravai Islands in the Low Archipelago in the South Pacific. The description 

 he gives of these specimens agrees very closely with those from Chilka Lake. He 

 had been able to compare his specimens with some from Monte Video and states 

 that the indentation in the palm of the second gnathopod of the male is less marked 

 in the Monte Video than in the Mediterranean specimens, while it is hardly notice- 

 able in his specimens from the Low Archipelago and apparently completely absent 

 in those from the Hawaiian Islands referred to 0. platensis by Stebbing. To this it 

 should be added that the male specimen from the Hawaiian Islands which Stebbing 

 refers to 0. pickeringii has the palm distinctly divided into two lobes. Walker 

 records 0. platensis from Mahlosmadulu Atoll in the Indian Ocean; the brief descrip- 

 tion he gives agrees well with the Chilka Lake specimens. He states (1905, p. 119) 

 that the specimens were obtained at a depth of 20 fathoms, but it is to be pre- 

 sumed that there was some error in the locality label. 



Walker says that 0. anomala Chevreux, from the Seychelles, appears to differ 

 from 0. platensis only in the averted point of the dactyl of the second gnathopod 

 of the male, but in 0. anomala the palm is much more oblique and the finger longer, 



