3/8 FRESH- WATER DOLPHINS CHAP. 



The genus consists of some eight widely distributed species, 

 which are none of them large Dolphins. 



Lagenorhynchus has the following assemblage of characters : 

 Head with short, not very distinct beak. Dorsal and pectoral 

 fins falcate. Teeth small, twenty-two to forty-five in each half 

 jaw. Vertebrae ranging in number from se.venty-three to ninety- 

 two. Pterygoid bones either in contact or separate. There are 

 fifteen or sixteen pairs of ribs, of which six are two-headed. 

 Of this genus Mr. True allows eight species, which have been 

 increased by a ninth since the publication of his " Eevision." l 



Two species of Lagenorhynchus are known from our coasts ; 

 the rest are mainly southern in range. The British species are, 

 firstly, L. albirostris, a Dolphin of some 9 feet in length. It has 

 a large number of vertebrae, ninety-two in number. L. albirostris 

 is a rare species, the first record of its occurrence on these shores 

 being in 1834. Since that date some eighteen individuals have 

 been shot or stranded on the shores of the British Isles. The 

 second British species, L. acutus, differs in colour from the first. 

 As in the last, the upper parts are black and the under parts 

 white; but in L. acutus there is also a stripe on the flanks, 

 brownish in colour. It has fewer vertebrae, not more than 

 eighty-two. 



The next genus of Dolphins, Sotalia, is characterised by 

 Teeth tolerably large, twenty-six to thirty-five. The vertebral 

 formula is C 7, D 11 or 12, L 10 to 14, Ca 22. The pterygoids 

 are not in contact in the middle line. It has a distinct beak. 



Of this genus there are some six species (the exact number, as 

 in so many other genera, cannot be positively asserted), most of 

 which are fluviatile or estuarine in habit. They are also on the 

 whole characterised by their pale, if not actually white, coloration. 

 S. sinensis of the Amoy is white with pinkish fins. Sotalia 

 guianensis is American as its name denotes. It is figured by van 

 Beneden as of a pale brown colour. It is very abundant in the 

 Bay of Bio de Janeiro, and has the reputation of being a friend of 

 man like some other Dolphins. The natives hold that it will bring 

 to shore the bodies of drowned persons. The most singular species 

 of the genus is that recently described by Professor Kiikenthal 

 as S. teilszii. 2 This animal is purely fresh-water, being found in 



1 Bull U.S. Nat. Mus. No. 36, 1889. 

 - Zool. Jahrb. Syst. Theil, vi. 1892, p. 442. 



