1886.] Wood-Mason & de Niceville — On Gachar BTio^alocera. 343 



§ 3. It may perhaps be thought that there is some inconsistency in 

 thus claiming the Sotar first as an old course of the Sutlej and then of the 

 Jumna, but this is apparent, not real, for, as I have pointed out, the Sotar 

 takes its rise where the fans of these two rivers meet, and must, as long 

 as they were building up the deposits they are now excavating, have 

 constantly been receiving a supply of water from one or other of the 

 two. It so happens that the last change of course of both rivers, 

 previous to that change of condition which led to their excavating the 

 existing depressed channels, took the one into the Beas, the other into 

 the Ganges, and a dry bed is all that remains of what was once a large 

 river flowing through a fertile land. 



Conclusion. — I have now shewn that we may take it as proved that 

 there have been great changes in the hydrography of the Punjab and 

 Sind within the recent period of geology, that there are abundant indi- 

 cations, not amounting to proof, that these changes have taken place 

 within the historic period, and that the most important of them, by 

 which a large tract of once fertile country has been converted into 

 desert, appears to have taken place after several centuries of the Chris- 

 tian era had sped. It is hopeless to expect an authoritative settlement 

 of the question ; the physical conditions cannot be said to favour the 

 idea, but they are far from being inconsistent with so recent a drying up 

 of the " Lost River of the Indian Desert." 



XIX. — List of the Lepidojpterous Insects collected in Gachar hy Mr. J. 

 Wood-Mason, Part II, — Rhopalocera. — By J. Wood-Mason, Officiat- 

 ing Superintendent of the Indian Museum, and Professor of 

 Comparative Anatomy and Zoology in the Medical College^ Calcutta ; 

 and L. de Nice'ville, F. E. S. 



[Received and Read November 2nd, 1886.] 



(With Plates XV— XVIII.) 



Only one short paper on the Rhopalocera of Cachar has hitherto 

 appeared. It is by Mr. A. G. Butler, and it was published in the Trans- 

 actions of the Entomological Society of London for 1879. In it but 57 

 species are recorded, of which four are described as new to science, 

 namely, Salpinx grantii (which appears to be nothing more than one of 

 the almost innumerable slight variations of Euploea Jdugii), Mycalesis 

 lurida (which is in all probability a seasonal form of M. perseus or a 

 form transitional from the one to the other seasonal form of that species), 

 Lyccena {Zizera) squalida (to which the same remark applies, mutatis 

 mutandis), and Neptis cacharica, which has not since been recognized 



