90 ON A NEW DOLPHIN FROM BORNEO. [Feb. 19, 



although they have divided pterygoids, stating that he thinks it 

 desirable to await the examination of the complete skeleton before 

 placing them in the typical South-American genus Sotalia. All 

 three differ from the present form by their much larger teeth ; 

 while S.plumbeus and S.jjemiger (gadamu) are further distinguished 

 by their tall and falcate dorsal fins, and S. leniiginosus by its 

 speckled skin. The other Indian form, S. front atiis, is a true Steno, 

 with conjoint ptei'ygoids and rugose teeth. There are also many 

 other differences, such as variation in the number of teeth. 



As already mentioned, the specimen agrees with Sotalia and 

 differs from Steno (exclusive of the Indian forms referred to that 

 genus by Mr. Blanford) in the separation of the pterygoids. It 

 further agrees with the former in the relatively large number of 

 teeth and the smoothness of their enamel ; Mr. True giving the 

 number of teeth in Sotalia as from 26 to 35, and in Steno from 20 

 to 27. In Sotalia the number of vertebrae varies from 51 to 55, of 

 which 29 are precaudal : but in Steno the number is increased to 66, 

 of which 35 are precaudal. In its 30 precaudals the present 

 specimen agrees sufficiently well with Sotalia. 



It may therefore be taken that the specimen is not only referable 

 to the last-named genus, but likewise to the typical Brazihan 

 section of the same. The Indian forms (referred by Mr. Blanford 

 to Steno) have been already differentiated, while the white 

 Sotalia sinensis, in addition to its larger teeth, is readily distinguish- 

 able by its coloration. 



The South-American species, especially those from the Upper 

 Amazons, are probably sufficiently distinguished by their geo- 

 graphical distribution, but a few words may be added in regard to 

 them. Both Sotalia pallida and S.fluviatilis, of the Upper Amazons, 

 are broadly distinguished by the smaller number of their teeth, 

 there being |^ in the former and || in the latter. S.jmllida further 

 differs by the whitish colour of the upper -parts, while the peculiar 

 distribution of the colours forms another point of difference in 

 S. jiuviatilis. 



Comparison is more difficult in the case of the three forms 

 respectively known as S. tuciuvi, S. guianensis, and 'S'. brasiliensis. 

 The former of these is typified by two skulls in the British Museum 

 from the Upper Amazons, the number of teeth in which is '- 

 This form, if not identical with S. pallida, is probably very closely 

 allied. 



Sotalia brasiliensis, from Rio de Janeiro, was described on the 

 evidence of an immature specimen, and is said to be blackish above, 

 with the sides fulvous, the belly white, and the flippers coloured 

 like the back; the number of the teeth being l^. In many respects 

 this form appears to come very close to the one under consideration. 

 Sir William Flower was, however, of opinion that S. brasiliensis 

 might prove to be the young of S. Jiuviatilis. And apart from this, 

 the figures given by Van Beneden (reproduced in pi. iii. of 

 Mr. True's memoir) seem to indicate that the dorsal fin of 



