LEAVES FROM THE NOTE-BOOK OF A NATURALIST. 



87 



men, unless they have sounded all the shallows 

 and depths of testudinate life. 



But enough, arid, for the reader who is not 

 zoologically disposed, more than enough. He 

 has been led, if he has condescended to follow, 

 from the land to the marsh, from the marsh to the 

 lake, stream, and river, the residences of the ra- 

 rious modifications of testudinate life. A short 

 repose should be placed at his disposal, before, in 



the course of our narrative, he follows these great 

 rivers of the old and new world, in which the 

 fresh water tortoises disport themselves, into that 

 ocean in which all rivers, great and small, are 

 lost. But there, in that boundless waste of 

 waters, we shall find that Nature has modified the 

 Chelonian type into the Thalassian shape, which 

 occupies a distinguished reptilian place in the 

 present world, and in that which is gone forever,. 



THE extremities modified for walking on land, 

 in the case of the Chersians, shuffling about in 

 marshes and ponds in the case of the Elodians,* and 

 swimming in rivers with a good garnish of claws 

 to enable the Potamians f to scramble upon banks 

 and logs, to say nothing of the help of the said 

 claws in enabling them to secure their prey, take, in 

 the Thalassians,! an unmistakable oar-like shape. 

 No half-measures would enable a turtle to row 

 placidly on the mirror-like sea, when 



The air is calm, and on the level brine 

 Sleek Panope with all her sisters plays, 



or beat the billows when the ocean is agitated by 

 storms such as burst forth in tropical latitudes. 

 But these paddles have a double office to perform. 

 They are formed to act, not only as organs of 

 swimming, but as instruments of progression on 

 the tide-furrowed shore, when the females travel 

 up to deposit their eggs ; and to this end, in most 

 of the species, the paddle is furnished with one or 

 more nails, which greatly assist the animal in its 

 advance on land. 



Only five well-defined recent species are known, 

 if Mr. Gray be right in considering Chdone vir- 

 gata and Chelonc maculosa of Dumeril and Bibron 

 as varieties of Chdone mydas ; and this existing 

 state of the limitation of the marine form of these 

 reptiles opens a new and most interesting point 

 of view, when compared with the fossil evidences 

 of the development of this sub-family in the 

 ancient seas of our globe. Professor Owen, in 

 his valuable History of British Fossil Reptiles, 

 describes no less than eleven well-defined fossil 

 species of chelone found in Britain, to say nothing 

 of fragments. Such a catalogue, as he justly ob- 

 serves, leads to conclusions of much greater inter- 

 est than the previous opinions respecting the 

 chelonites of the London clay could have sug- 

 gested. 



Whilst (writes the professor) these fossils were 

 supposed to have belonged to a fresh water genus, 

 the difference between the present fauna and that 

 of the eocene period, in reference to the chelonian 

 order, was not very great ; since the Emys (cistuda) 

 Europew still abounds on the continent after which 

 it is named, and lives long in our own islands in 

 suitable localities. But the case assumes a very 

 different aspect when we come to the conviction 

 that the majority of the eocene chelonites belong 

 to the true marine genus chelone ; and that the 

 number of species of these extinct turtles already 



* Marsh tortoises. \ River tortoises. 



J Sea tortoises, or turtles. 



obtained from so limited a space as the Isle of 

 Sheppy, exceeds that of the species of chelone now 

 known to exist throughout the globe. 



The professor comes to no hasty conclusion, 

 when he states that the ancient ocean of the 

 eocene epoch was much less sparingly inhabited 

 by turtles than that which now washes the shores 

 of our globe ; and that these extinct turtles pre- 

 sented a greater variety of specific modifications 

 than are known in the seas of the warmer lati- 

 tudes of the present day. Nor does the inference 

 stop here ; for, as he well says in continua- 

 tion, the indications which the English eocene 

 turtles, in conjunction with other organic remains 

 from the same formation, afford of the warmer 

 climate of the latitude in which they lived, as 

 compared with that which prevails there in the 

 present day, accord with those which all the 

 organic remains of the oldest tertiary deposits 

 have hitherto yielded in reference to this interest- 

 ing point. We have already seen that some of 

 the fresh-water tortoises make the eggs and young 

 of crocodilians and other reptiles their prey, and 

 the conformation of some of these fossils furnishes 

 the author of the work here cited with another 

 generalizing observation. 



After remarking that abundance of food must 

 have been produced under the influences of a 

 climate such as that which the fossil turtles en- 

 joyed, he proceeds to the inference that to some 

 of the extinct species which, like the Chelone 

 longiceps and Chelone planimentum, exhibit a form 

 of head well adapted for penetrating the soil, or 

 with modifications that indicate an affinity to the 

 Trionyces was assigned the task of checking the 

 undue increase of the now extinct crocodiles and 

 gavials of the same epoch and locality, by de- 

 vouring their eggs or their young, the trionyces 

 themselves becoming, probably in return, an occa 

 sional prey to the older individuals of the same 

 carnivorous saurians. Thus did the lex talionis 

 prevail long before lawyers stained paper with 

 their well-galled ink. Thus was the balance 

 kept up in bygone ages as it now is. The same 

 principle of mutual extermination was, and is, 

 and is to be ; and by this principle, which to the 

 uninitiated must wear somewhat of an Acheroatic 

 aspect, the greatest quantity of general happiness 

 is secured in what would otherwise be an over- 

 crowded world : but VCR victis. 



The well-arched, thick-walled, wagon-proof, 

 portable castle, assigned by the distributive justice 

 of Nature to the larger slow land tortoises, and 



