REPTILES 'IN GEOLOGY - 145 



Reptiles in Geology 



Except the Tuatera all our modem reptiles be- 

 long to families that are comparatively recent. The 

 crocodUians, however, kad ancient representatives. 

 If thisk order were not one of the families of the old 

 order of Dinosaurs, it was close to them. They 

 occur just above the coal — after the age in which the 

 Eeptiles all came in. It is probable that they are 

 now (and were then) a slightly degraded form, and 

 got the hole between the two great ..heart arteries by 

 going back to the water after having been once 

 more terrestrial. 



The tortoise-forms are not found farther back 

 than the rocks which are just below man — the so- 

 called Tertiary times. They are evidently just lizards 

 with shells on the back. As noted, many lizards show 

 bones on the back under the skin, and other lizard- 

 forms have in the abdomen bones which are not 

 part of the breast-bone ; some have beaks quite like 

 those of the turtles, but the teeth are still 'present. 

 One turtle, however, shows a tooth or two in its very 

 young. Finally, a small fossil burrowing lizard has 

 been found by Professor Cope which had a shell on top 

 only. A giant fossil turtle was found out West thir- 

 teen feet long and it had flippers which measured from 

 tip to tip about fifteen feet. Like the sea-turtle its 

 ribs were flattened but were not grown to the shell. 



Snakes are found in the lowest Tertiary — perhaps 

 a little older than the tortoise-forms. They are but 

 lizards with the legs lost and the chin loose- jointed. 



