CRETACEOUS PERIOD 101 



communicated with the windpipe, by running through the 

 bony palate into the mouth ; and to keep the mouth open 

 under water would have been suicidal. To achieve the object 

 in view, the anatomy had been considerably modified. The 

 nasal passages had been carried further back ; and could, 

 with the windpipe, be shut off from the mouth by means of 

 valves at the back of the tongue. A want long felt by croco- 

 diles enablement to drown prey without risk of self-drown- 

 ing had, therefore, been supplied. 



Alligators seem to have been in existence at this time ALLIGATORS 

 (Bottosaurus). These creatures were probably an offshoot 

 of the crocodiles. Indeed, excepting for the manner in 

 which some of the lower teeth bite into the upper jaw, 

 alligators are practically identical with short-snouted croco- 

 diles. 



The sea-roving crocodiles (Metriorhynchus) of the last SEA-ROVING 

 Period were no longer represented. Possibly they never CROCODILES 

 became sufficiently expert swimmers for the manner of life 

 they had adopted. 



In some parts of Europe, however, reptiles of a different DOLICHO- 

 type had betaken themselves more or less to a watery life. SAURS 

 These were probably modified descendants of some of the 

 semi-lizard creatures of Triassic times. In some respects they 

 were developing in the direction of snakes. These dolicho- 

 saurs, or " long lizards " as they are called, did not, in early 

 Cretaceous times, exceed a yard in length ; but in the 

 course of the Period, forms of twice and even thrice that 

 length were in the waters (Dolichosaurus). They never 

 became so far modified in their limbs as to become completely 

 adapted to aquatic life. 



In late Cretaceous times some thorough sea-going reptiles MOSASAURS 

 probably an offshoot of the " long lizards " were abroad. 

 These creatures have been named Mosasaurs, as remains of 

 them were first found in the valley of the Meuse, or Mosa. 

 Subsequent discoveries have shown that they were by no 

 means confined to that region ; but that they lived also in 

 seas of North and South America, and extended their range as 

 far as New Zealand. They possessed skulls lizard-like in 

 shape, and long, snake-like bodies. Their limbs had become 



