13 



Western Himalayas, and of (b) Assam and Burma. Both these differences — 

 the former quite clearly, and the latter a difference seen beneath a likeness — 

 are brought out in a study of the fresh-water crabs. 



(4) The presence in the Malabar tract of forms that do not occur in other 

 parts of the Peninsula, or even in any other part of the Indian political area, 

 and " the remarkable fact " that, beyond these forms restricted to the Malabar 

 tract, there are many Himalayan or Burmese (or both) mammals and birds that 

 are found in it and not in the Peninsula. Blanford also devotes a special note 

 to the vertebrate genera that occur in India and Burma but not in the 

 Himalayas. All three points, namely — (1) a close correspondence of genera 

 (but not of species) betvceen the Peninsula and the territory east of the Indo- 

 Gangetic Plain to the exclusion of the plain itself; (2) a specially intimate 

 correspondence between the Malabar tract and the said eastern territory ; and 

 (3) the restriction of certain forms to the Malabar tract ; — -are well illustrated 

 by the fresh-water crabs. The evidence for these conclusions is presented in 

 the following list of Indian Potamonidae arranged geographically. 



Geographical List of the Indian Potamonid^. 

 1. western frontier territory. 



(Baluchistan and N.-W. Frontier Province.) 



1. Potamon fliivialile var. ibericum. 3. Potamon sp. 



2. „ „ var. gedrosiamivi. 4. Paratelphum blanfordi. 



2. WESTERN HIMALAYAN TERRITORY. 

 (Himalayas eastwards as far as Nepal.) 



1. Potamon athinsonianum. 4. Polamon koolooense. 



2. „ „ var. emphyseleum. 5. Paratelphusa (Barijtelphusa) masoniana (at 



3. ,, „ vai'. ambivium. Naini Tal). 



3. NORTH-EASTERN FRONTIER TERRITORY. 

 (SiKKiM, Bhutan, and the Lower Brahmaputra Drainage-System.) 



1. Potamon Jluviatile var. monticola. 18. Paratelphusa spinigera. 



2. Potamon atkinsonianum. 19. Parateiphima trilobata. 



3. Potamon tnfarium. 20. Paratelphusa {Barytelphnsa') edentula. 



4. Potamon ander.sonianum. 21. „ „ sp. prox. edentula. 



5. „ „ var. asperatum. 22. „ „ nap«a. 



6. „ „ var. manipurense. 23. „ „ lugubris. 



7. Potamon pealianum. 24. „ „ „ var. nigerrima. 



8. „ „ var. antennaiizim. 20. „ „ „ var. plauta. 



9. Potavion (.'') tumiduluvi (or Potamiscus). 26. „ „ falcidmtis. 



10. Potamon austenianum. 27. „ „ harpax. 



11. Potamon {Potamiscus) siUimense. 28. Paratelphusa {Phricotelphusa) gageii. 



12. „ „ annandaUi. 



29. Paratelphusa [Liotelphusa) Iwiis. 



13. Potamon (Geotelphusa) adiatretum. 30. „ va.r. auadrata 



14- „ „ sp. 31. Paratelphusa (Globitelphusa') ba/ceri. 



15. Potamon {Acanthotelphusa') wood-masoni. 32. „ „ , var.ci/lindn/s 



16. „ „ fungosum. 33. „ „ pistorica. 

 l*^- « » fro:- 34. Paratelphusa {Oziotelphusd) sp. 



