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 seventy-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 "Revision."[1]
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 Rio 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 Kükenthal as S. teüszii.[2] This animal is purely fresh-water, being found in
