CHELONIA. 



359 



commencement of the Tertiary epoch. The earliest known 

 traces of Chelonians occur in the Permian Rocks, in the lower 

 portion, that is, of the New Red Sandstone of older geologists. 

 These traces, however, are not wholly satisfactory, since they 

 consist solely of the footprints of the animal upon the ripple- 

 marked surfaces of the sandstone. Of this nature is the 

 Chclichnus Dnncani, described by Sir William Jardine in his 

 classical work on the 

 ' Ichnology ' of Annan- 

 dale in Dumfriesshire. 

 With doubtful excep- 

 tions, the first unequi- 

 vocal remains of Che- 

 lonians appear in the 

 Jurassic series. The 

 Chcloniida make their 

 first undoubted ap- 

 pearance with the Che- 

 lone planiceps of the 

 Portland stone (Upper 

 Oolite). In the Cre- 

 taceous series are seve- 

 ral turtles, one of which 

 is figured below (fig. 

 314). In the Tertiary 

 Rocks the remains of 

 Turtles are abundant, 

 and especially so in the 

 London Clay (Eocene). 

 Species of Emydida 



have been Cited from F 'S- y-^Cltelone Benstedi. Lower Chalk. 



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, es- 

 pecially in the Eocene and Miocene. The Trionycida, 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 Testudinida or Lar/d-tortoises appear to 

 have commenced their existence in me Miocene Tertiary. 

 The most remarkable form of this group is the great Colosso- 

 chelys Atlas of the Tertiary deposits of the Sivalik Hills, which 

 is believed to have reached the gigantic length of twenty feet. 



