SQUAMATA 145 



air for respiration. Of one of these swimming species Annandale 

 writes: 



Varanus salvator is common in Lower Siam where it is equally at home on 

 land, in water, and among the branches of trees. The eggs are laid in hollow 

 tree trunks. When in the water the lizard swims beneath the surface, the legs 

 being closely applied to the sides, and the tail functioning both as oar and 

 rudder. 



These lizards take to the water to escape from their land 

 enemies and not for food, a habit also known among certain other 

 lizards, and one precisely the reverse of that of the Galapagos 

 lizards. It would seem very probable that animals of such carniv- 

 orous habits as are the monitors might easily learn to capture 

 water animals for food and thus eventually become aquatic in 

 habit. This incUnation toward, and partial adaptation to, water 

 habits in the monitors is of much interest because in all probability 

 the instinct is one of long inheritance from those remote ancestors 

 which gave origin to the truly aquatic members of the order. 

 Though the known geological history of the monitors does not 

 extend far back, they are so intimately. alUed in their anatomical 

 structure to the aquatic and semiaquatic lizards of Cretaceous 

 times that there could seem to be no doubt of the common ancestry. 



Dolichosaurs. — About fifty years ago Professor Owen, the famous 

 English paleontologist, described a peculiar semiaquatic Uzard 

 from the Cretaceous rocks of England to which he gave the name 

 Dolichosaurus, in allusion to the slender form of the body. Just 

 what relations these slender lizards have to modern lizards has long 

 been a problem; some have thought that they were their pro- 

 genitors, but there are very good reasons for doubting this. No 

 modern lizards, save the monitors, have more than eight vertebrae 

 in the neck, while these dohchosaurs had as many as seventeen, a 

 remarkable speciahzation for aquatic life that could hardly have 

 been lost by their descendants. For this reason the dohchosaurs 

 have usually been considered as representing a distinct suborder. 

 ■But they have many resemblances otherwise to the monitors. 

 They were semiaquatic in habit, and. never more than six feet 

 in length. They are yet imperfectly known, and no restoration 

 of any form has hitherto been attempted. Their pecuhar interest 



