265 



CHAPTER XT. 



nPHE extremities modified for walking on land in the 

 -■- case of the Chersians, shufEing 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 Tha]assians,J an un- 

 mistakeable 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 Chelone virgata and Che- 

 lone "maculosa of Dumeril and Bibron as varieties of 

 Chelone my das; and this existing state of the limitation 

 of the marine form of these reptiles opens a new and 



* Marsh tortoises. f River tortoises. 



X Sea tortoises, or turtles. 



N 



