PERFECT SKELETON OF KHTTII^A GIGAS. 469 



Passing to the West Indies, we find a fossil species from thence 

 having important differences in dentition, by which to separate it 

 from the now living Manati. Three other species occur in the 

 Tertiary beds of South Carolina : and a doubtful form in the deposits 

 of Darling Downs, Queensland, Australia. 



Lastly, there is the extinct Rliytina of Behring's Island now under 

 notice. We have, then, at the present day living in America, 

 Africa, India, and J^T.E. Australia, two genera and six species of 

 Sirenia ; and in Europe, Africa, and America, 12 genera and 27 

 species of extinct Sirenians. 



Conclusion. — Distribution of the Sirenia. — There are, it appears 

 to me,' two very important points in connexion with the Sirenia 

 which are worthy of our special attention as geologists and palaeon- 

 tologists. 



I allude to the present and the past distribution of this order 

 over the world. 



If we take the belt of the tropics, that is 23|° N. and 23^° S. of 

 the equator (or, better stiU, say 30° JS". and S. of the equator), ive 

 shall cover the geographical clistrihution of all the living Sirenians. 



If we take another belt of 30° North beyond the tropic of Cancer, 

 we shall embrace the ivhole geographical area in luhich fossil remains 

 of Sirenians have been met luith. 



Assuming, as I think we may, that the Sirenia at the present day 

 belong exclusively to the tropical regions of the earth, and that Rhytina, 

 in its boreal home, was simply a surviving relic from the past (a 

 sort of geological " outlier" as of a stratum elsewhere entirely 

 denuded away), we must conclude that the presence of about 12 genera 

 and 27 species of fossil Sirenia, as widely distributed then as the 

 recent forms are at the present day, but with a range from the tropic of 

 Cancer up to 60° of north latitude., affords a most valuable piece of 

 evidence (if such were needed), attesting the former northern 

 extension of subtropical conditions of climate which must have 

 prevailed over Europe, Asia, and N. America, in Eocene and 

 Miocene times and in the older Pliocene also. 



The early appearance of so highly modified a form of mammal, 

 its abundance, distribution, and variations, serve to attest the great 

 lapse of time occupied in the accumulation of even our later Tertiary 

 deposits, which we are sometimes apt to pass over as representing but 

 a very brief chapter in the geological history of our earth ; and 

 further, it must necessitate our carrying back the Mammalian class 

 far into Secondary times. 



Note. — Drifted remains of Manatee (either from Elorida or from 

 the West Indies) are recorded as having reached our shores, 

 probably on the waters of the " gulf-stream," in 1785. 



The carcass of one of these animals was washed ashore at Leith ; 

 it was much disfigured, but Mr. Stewart informed Dr. Eleming 

 that it was the putrid body of a Manatee, or Manatus borealis, 

 (EeU, Brit. Quadrupeds, 8vo, 1837, p. 525.) 



Q. J. a. S. m. 163. 



