758 



G. PILLERI UND M. GIHR 



La hauteur caudale de la crista maxilliaire constitue un second caractère 

 distinctif. Elle est plus grande — tant à droite qu'à gauche — chez les dauphins 

 du Gange et du Brahmapoutra que chez le dauphin de l'Indus. 



Chez le dauphin fluviatile indien, il existe un dimorphisme sexuel prononcé 

 dans le développement du rostre. Contrairement aux conclusions de Blyth (1859). 

 notre matériel ostéologique du Brahmapoutra nous a permis de confirmer pleine- 

 ment l'assertion d'ANDERSON (1878), selon laquelle les femelles auraient un rostre 

 plus long que les mâles. 



SUMMARY 



Thirty-eight measurements have been made on the skulls of six river dolphins 

 from the Indus and of six other individuals from the Brahmaputra, and they have 

 been compared with the muséum material (17 spécimens). 



On the base of new taxonomic characters found by comparing the animais 

 of the Indus with those of the Ganges, the séparation into two distinct species 

 Platanista indi and P. gangetica appears as justified. This speaks against the vievv 

 of Anderson (1878) that both belong to the same species, and réhabilitâtes the 

 concept of Blyth (1859) of the existence of two species. A particular and constant 

 morphological character is the Crista nasalis, which is formed on the vostro-dorsal 

 border cf the neuro-cranium by the two frontalia, and which is considerably 

 lower in Platanista indi than in P. gangetica. 



A second character consists of the caudal height of the maxillary crista, which 

 is greater in the dolphins from the Ganges and from the Brahmaputra, than in 

 the Indus-dolphin. 



In the Indian river dolphin, a marked sexual dimorphism exists in the 

 development of the rostrum. Against the conclusions of Blyth (1859), our 

 osteological material from the Brahmaputra confirmed fully the affirmation of j 

 Anderson (1878), that female animais have a longer rostrum than the maies. 



LITERATUR 



Anderson, J. 1878. Anatomical and zoological researches; comprising an account of the 

 zoologie al resuit s of the two expéditions to Western Yunnan in 1868 

 and 1875 and a monograph of the two cetacean gênera, Platanista and 

 Orcella. 2 vols., B. Quaritch, London, 985 pp. 

 and W. L. Sclater. 1881-1891. Catalogue of the Mammalia of the Indian Muséum 

 Calcutta. 2 vols., Indian Muséum, Calcutta. 



Blyth, E. 1859. On the Great Rorqual of the Indian Océan, with notices of other Cetals, 

 and of the Sirenia or marine Pachyderms. J. Asiat. Soc. 28: 481 — 498. 



