566 FOSSIL SAURIANS; PTERODACTYLUS; ICTHYOSAURUS. 



The Acontias, or Javelin Snake, of Southern Africa, is nearly 

 allied to our Slow-worm. 



503. We have now to advert to some extraordinary Reptiles 

 of a past age ; which establish, in a remarkable manner, the 

 connection between this class and the other Vertebrata. The 

 remains of the Pterodactylus (Fig. 307), the chief peculiarity in 

 whose structure has been already noticed ( 468), are found in 

 the lias and oolite formations ; mingled with the remains of large 

 insects, such as Dragon-flies and Beetles. There can be no 

 doubt that they were adapted to lead the life of the Bats and 

 Swallows of the present day ; restraining the multiplication of the 

 Insect tribes, at a period when neither Birds nor Bats existed. 

 Some of the larger species may not improbably have been partly 

 aquatic in their habits, and may have fed on fish. From the 

 size and form of the posterior extremities, the Pterodactylus 

 seems to have been able to walk arid perch upon them, after the 

 manner of Birds ; and with the anterior and posterior combined, 

 it could probably walk and climb on rocks and cliffs, like Bats 

 and Lizards. Several species have been already found, and more 

 probably remain to be discovered ; their size varied from that of 

 a Snipe to that of a Cormorant. One of these was remarkable 

 for the enormous length of its head ; in all of them the neck was 

 very long, and thus enabled the head to make a sudden dart 

 upon the prey. 



504. In the same deposits, we find the remains of numerous 

 species of Icthyosaurus, or Fish-Lizard ; the whole organisation 

 of which shows its intermediate position between the Reptiles, 

 Fishes, and Cetaceous Mammalia. The spinal column is formed 

 upon the plan of that of the Fish ; the vertebrae being concave 

 on both surfaces, and having had a bag of fluid interposed 

 between each pair ( 66) ; and the arches which enclosed the 

 spinal chord always remained distinct from the bodies. Hence 

 the body must have had great flexibility, and must have been 

 able to move rapidly through the water by its undulations from 

 side to side ; whilst the spinal column could not have been 

 sufficiently strong to support the weight of the trunk upon land. 



