602 



KEPTILIA 



[CH. 



species in the southern states of North America, the Alligator, 

 Alligator mississipiensis, which has a much shorter and broader 

 snout than the Crocodile. This animal lies for hours absolutely 

 motionless at the surface of the water so as to greatly resemble a 

 log, and. thus entrap any unwary animal which may venture near. 

 The Gavial, Gavialis gangeticus, in India is remarkable for its 

 excessively long and narrow jaws. 



So far as we can learn from fossils the Reptiles seem to have 

 been the dominating type of land animals in the ages which inter- 



3 ^^*^- 4 



FIG. 300. A. Left half of the pectoral girdle of an Alligator, Caiman lati- 



rostris x-f . 



1. Scapula. 2. Coracoid. 3. Interclavicle. 4. Glenoid cavity. 



B. Pelvis and sacrum of an Alligator, Caiman latirostris x \. 



1. Ilium. 2. Ischium. 3. Acetabular bone. 4. Pubis. 5. Aceta- 

 bular foramen. 6. Neural spines of sacral vertebrae. 7. Union of 



the two ischial bones. 8. Process bearing prezygapophysis. 



vened between the close of the Coal epoch and the end of the Chalk 

 period when the white limestone which constitutes the southern 

 cliffs of Britain was deposited as a sediment in the quiet waters 

 which covered what is now Western Europe. A rough sketch of 

 the history of the class as deduced from fossils may be given here. 



The Reptilia seem to have arisen from the most primitive forms 

 included under the title Stegocephala. At least there are some 

 forms like Eryops and Cricotus included in the latter group in which 

 the bones flanking the notochord, which have not yet united so as to 



