MANATUS, ° 91 
as a perfectly distinct order of Mammalia, only distantly connected with any other 
form, but having most affinities with the Ungulates and Proboscideans. As to their 
distribution, the two existing genera are confined to the shores of the tropical and sub- 
tropical seas—Manatus to the Atlantic, and Halicore to the Indian Ocean and parts of 
the Pacific—while Rhytina was till lately a native of the icy waters of Behring Straits. 
Fam. I. MANATIDZ. 
1. MANATUS. 
Manatus, Storr, Prod. Meth. Mamm. p. 41 (1780, part. ex Rodelentia) ; Illiger, Prod. Syst. Mamm. 
p. 140 (1811)*. 
The genus Manatus may be at once distinguished from its nearest ally, Halicore, by 
its rounded tail-fin, and by the presence of rudimentary nails on its flippers, as well as 
by many important features of its internal organization. Thus, the whole shape of the 
skull is very different, there are no incisors in the permanent dentition, and only six 
cervical vertebre are present, forming one of the few known exceptions to the usual 
number in the Mammalian class. The anatomy of the American Manatee has been 
studied by various eminent zoologists +, and may now be considered to be as well known 
as that of most tropical Mammals. 
Several species of Manatee have been described from time to time; but further 
investigation has disposed of the claims of all save two—the Manatus australis (or 
americanus) of the western, and the WW. senegalensis of the eastern coasts of the tropical 
Atlantic. Nor is the specific distinctness of these two forms at all clearly demonstrated ; 
for most of the osteological differences pointed out by Cuvier and his followers were 
found to disappear when sufficient series of specimens were compared by Professors 
Schlegel £ and Brandt § and Drs. Krauss || and Gray §. The last-named writer fell 
back on a single character, which he himself acknowledged not to be absolutely 
constant, namely the state of the rudimentary nasals, which are usually sufficiently 
developed in WM. australis to make a pit or hollow in the anterior edge of the frontals, 
whereas in J. senegalensis they are either absent or so small as not to leave any 
impression on the other bones. But the fine Cuban skeleton in the Museum of the 
* Manatus of Storr appears to have included the “ Manati” of Steller (Rhytina), and, by implication, the present 
genus, the Dugong being separated as Trichechus. Liger was the first writer who characterized the genera of 
Sirenia in a scientific manner ; and his names have been so generally adopted that much inconvenience would be 
caused by any change. The transference of the Linnean name T'’richechus from the Walrus to the Manatee has 
been recently proposed, but on what appear to me to be totally inadequate grounds, 
+ Among these may be especially mentioned :—Brandt, Mém. Ac. Pétersb. 6™¢ sér. v. pp. 134-137, & 7™e sér. 
xii. pp. 242-253; Vrolik, Bijdr. tot de Dierkunde, i. art. 5; Krauss, Arch. f. Anat. 1862, pp. 415-427; Murie, 
Trans. Zool. Soc. viii. pp. 127-202, & xi.(in the press); and Garrod, op.cit. x. pp. 137-145, 
t~ Abhandl. Zool. u. vergl. Anat. i. pp. 9-13. § Mém. Ac. Pétersb. 7™°¢ sér. xii. p. 241. 
|| Arch, f, Anat. 1858, pp. 390-425. q Ann. & Mag. Nat. Hist. 3rd ser. xv. pp. 130-139. 
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