OECELLA. 369 



Orcella brevirostris, Owen. 



GlobiocepAalus indicus^Bljih. (in part), Journ. As. Soc. vol. xxi. 1852, p. 358; ibid, xxviii. 1859;, 



p. 490; Cat. Mamm. As. Soc. Mus. 1863, p. 89, No. 274, C and D; Jerdon, Mamm. Ind. 



1867, p. 160 (in part). 

 Thocmna {Orca, Gray, Eeinhart) brevirostris, Owen, Trans. Zool. Soc. Lond. vol. vi. 1869, 



p. 24, et. seq. pi. ix. figs. 1, 2, 3. 

 Orca {Orcaella, Gray) brevirostris, Owen, Gray, Cat. Seals and Whales, B. M. 1866, p. 285; Proc. 



Zool. Soc. Lond. 1870, p. 7]. 

 Orcella brevirostris, Andr. Proc. Zool. Soc. Lond. 1871, p. 143, %. 1. 



In 1850 Blyth described a round-headed whale from a male and female belong- 

 ing to a school numbering about 20 individuals, which was stranded in the salt lakes 

 to the east of Calcutta, during an extraordinary high tide. This whale, which 

 Blyth called Globiocephalus indicus, is closely allied to, although distinct from, the 

 Em^opean G. deductor, which it equals in dimensions. 



In 1852 he received another round-headed dolphin from Serampore, measuring 

 only 78 inches in length and regarded it as the young of G. indicus, and in 1859 he 

 obtained a small female in the Calcutta bazaar and converted it into a skeleton, con- 

 sidering it also to be the young of G. indicus. In tliis, however, he was mistaken, 

 as the skeleton proves them to be nearly adult, and to be generically distinct from 

 Glohicephalus. Jerdon in his Mammals of India adopted Blyth's opinion regardins;^ 

 the identity of the Serampore dolphin with G. indicus. 



Professor Owen was the first to describe this dolphin, but his only materials 

 were the skull of an animal which was thrown ashore in the harbour of Vizaga- 

 patam in too decayed a state to be figured, but which Sir Walter Elliot's notes 

 described as having a round head, without a beak. Mr. Blyth's Serampore dolphin 

 is proved to be this species, as its skull and the skull of the specimen procured in 

 the Calcutta bazaar agree with Owen's figure of O. brevirostris, and the condition 

 of the bones of the skeleton and the state of the teeth of the latter specimen are 

 those of an adolescent and not of a newly born female as supposed by Blyth. 



Distribution. — This dolphin is apparently of frequent occurrence in the estu- 

 aries of the Ganges and Brahmaputra, but I am not aware that it has as yet been 

 observed in portions of the rivers beyond the influence of the tides, and in this it 

 markedly differs in its habits from Orcella fluminalis. It would appear to be a 

 species confined as far as is at present known to the Bay of Bengal, and to frequent 

 the estuaries of the larger rivers falling into it. It is probably to an estuarine 

 habit that we have to look for an explanation of the origin of a round-headed dol- 

 phin in the Irawady rather than to the isolation of individuals from a marine stock 

 by changes in the physical configuration of the estuaries themselves, although at the 

 same time if these animals in estuaries become localised in their habits, the seaward 

 extension of a delta and the slow change of the water from brackish to fresh might 

 gradually give rise to a fluviatile species. It may be, however, that both these 

 causes are contributing in the Ganges to the production of a river species of round- 

 headed dolphin like that of the Irawady. 



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