REPTILIA. 197 



reach the Jurassic period that we meet with unequivocal 

 remains of Chelonian Reptiles. Here the true Turtles {Chcl- 

 oniidm) make their first undoubted appearance with the 

 Chclone planiceps of the Portland Stone (Upper Jurassic). 

 In the Cretaceous series we have evidence of the existence 

 of numerous forms of Chelonians, one of which is here 

 figured. It is also in deposits of this age that the earliest 

 traces of Chelonians that have yet been found in North 

 America occur. Some of these {e.g., Atlantoclielys) are forms 

 allied to the true Turtles, while there are other genera related 

 to the Emydidce. 



In the Tertiary rocks the remains of Turtles are abundant, 

 and especially so in the London Clay (Eocene). Species of 

 Emydidce have been cited from the Jurassic series, some of 

 which appear to be free from doubt. A species of Emys 

 occurs in the Wealden, and numerous forms of this family 

 have been detected in formations of Tertiary age, especially 

 in the Eocene and Miocene. The Trionyddce, except for a 

 femur described by Owen from the Lias, are not known to 

 have existed prior to the commencement of the Tertiary 

 period. Numerous species of Trionyx, however, occur in the 

 Eocene, and others have been described from the Miocene 

 and Pliocene. The Tcstudinidce or Land-tortoises appear to 

 have commenced their existence in the Miocene Tertiary. 

 The most remarkable form of this group is the huge Colos- 

 sochclys Atlas of the Upper Miocene ( ? Pliocene) deposits of 

 the Siwalik Hills in India, described by Dr Falconer and Sir 

 Proby Cautley. Far exceeding any living Tortoise in its 

 dimensions, this enormous animal is estimated as having had 

 a length of about twenty feet, measured from the tip of the 

 snout to the extremity of the tail, and to have stood up- 

 wards of seven feet high. All the details of its organisation, 

 however, prove that it must have been " strictly a land 

 animal, with herbivorous habits, and probably of the most 

 inoffensive nature." The accomplished palaeontologists just 

 quoted, show, further, that some of the traditions of the 

 Hindoos would render it not improbable that this colossal 

 Tortoise had survived into the earlier portion of the human 

 period. The largest living Tortoises are found in the Gala- 



