THE ROMANCE OF NATURAL HISTORY. 



dies.* It is a pity that no estimate, even ap- 

 proximate, of the dimensions is given ; but as the 

 alligator affords the comparison as to form, it is 

 most probable that there was a general agree- 

 ment with it in size. This might make it some 

 twelve or fifteen feet in length. 



I cannot, then, admit that either the general 

 substitution of Cetacea for EmiHosauria in our 

 era, or the absence of remains of the latter in the 

 tertiary deposits, is sufficient evidence of their 

 non-existence in our seas; any more than the 

 general replacement of Placoid and Ganoid fishes 

 by the Cycloids and Ctenoi'ds, or the absence of 

 the former two from the tertiaries, is proof of 

 their present non-existence. 



It must not be forgotten, as Mr. Darwin has 

 ably insisted, that the specimens we possess of 

 fossil organisms are very far indeed from being a 

 complete series. They are rather fragments acci- 

 dentally preserved, by favouring circumstances, in 

 an almost total wreck. The Enaliosauria, par- 

 ticularly abundant in the secondary epoch, may 

 have become sufficiently scarce in the tertiary to 



* Dr. J. E. Gray Jong ago expressed his opinion that some un- 

 described form exists, which is intermediate between the tor- 

 toises and the serpents. M There is every reason to believe, from 

 general structure, that there exists an affinity between the tor- 

 toises and the snakes; but the genus that exactly unites them 

 is at present unknown to European naturalists; which is not 

 astonishing when we consider the immense number of un- 

 described animals which are daily occurring. Mr. Macleay 

 thought that those two orders might be united by means of 

 Emys longicollis (the long-necked tortoise) of Shaw ; but the 

 family to which this animal belongs appears to be the one which 

 unites this class to the crocodile. If I may be allowed to specu- 

 late from the peculiarities of structure which I have observed, I 

 am inclined to think that the union will most probably take 

 place by some newly discovered genera allied to the marine or 

 nuviatile soft-skinned turtles, and the marine serpent." 



t "Synopsis of Gen. of Reptiles.'" in Ann. of Philos., 1825. 

 340 



