466 Records of the Indian Museum. [Voi,. XXIV, 



with spines instead of smooth, and in having the sterna of some 

 of the thoracic and abdominal somites furnished with median pro- 

 cesses. In the present species the sterna of the last six thoracic 

 somites are furnished with long sharply pointed forwardly directed 

 processes as shown in the accompanying figure (text-fig. in), the 

 lower margin of which is furnished with numerous spinous pro- 

 cesses. The sterna of the first four abdominal somites are fur- 

 nished with simple papilliform processes. 



The species, H. spinifera, therefore agrees absolutely with 

 the characters of the genus Hyper erythrops as distinguished 

 from Erythrops and is closely allied to the type species, H. serri- 

 venter H. and T. It may, however, be distinguished from the 

 latter by its smaller size, the different form of the antennal scale, 

 which is narrower and has the terminal lobe much less developed 

 than in the type, and by the different shape and spinulation of the 

 telson. 



One other feature of the genus Hypererythrops must be men- 

 tioned. In the pleopods of the male there is a broad flat branchial 

 plate, devoid of setae, at the base of the endopod, which appears 

 to arise from the short setiferous lobe characteristic of the endopod 

 of the pleopods of Mysidae. The form of this branchial plate in 

 H. spinifera is shown in (text-figs, n/, g.) I have re-exarained 

 some specimens of H. serriventer, and find that a similar branchial 

 plate, larger in size, is present on the male pleopods. I do not 

 know of a similar development among the Erythropini and it is 

 interesting to note that it is present in the European and the 

 Indian species of this genus. Its presence forms an additional 

 character separating the genus from Erythrops. These branchial 

 plates recall the pseudo-branchial processes on the pleopods of 

 the species of Siriella and, in point of fact, on the first pleopod 

 of the male of H. spinifera the branchial lamella is bilobed as in 

 so many of the species of Siriella. But in the remaining pleopods 

 it is a simple broadly expanded plate without setae. 



Distribution. — Hansen's specimens were found in the seas 

 of the East Indian Archipelago. The occurrence of this genus, 

 hitherto known only from European waters, in the waters of 

 the Indian Ocean is a matter of great interest. 



Tribe Leptomysini. 

 Genus Mysidopsis G. O. Sars. 

 Mysidopsis indica, sp. nov. 

 Text-figs. I2a-e. 



Locality. — Port Blair, Andaman Islands, Station 5. Two 

 males and two females, 4 mm. (Types.) 



Description. — Very closely allied to Mysidopsis gibbosa G. O. 

 Sars. It will be sufficient to refer to Sars' description of this 

 species (1870-79) and to point out the following differences : — 



