MESOZOIC ERA: THE AGE OF REPTILES 557 



REFERENCES FOR MARINE REPTILES 



ICHTHYOSAURS 



Hutchinson, H. N., — Extinct Monsters and Creatures of Other Days, pp. 59-75. 

 Lankester, E. R., — Extinct Animals, pp. 225-229. 



Osborn, H. F., — Ichthyosaurs: Century Mag., Vol. 69, 1905, pp. 414-422. 

 Williston, S. W., — Water Reptiles of the Past and Present, pp. 107-125. 



Plesiosaurs 



Hutchinson, H. N., — Extinct Monsters and Creatures of Other Days, pp. 78-84. 

 Matthew, W. D., — The New Plesiosaur: Am. Museum Jour., Vol. 10, 1910, pp. 



246-250. 

 Williston, S. W., — Water Reptiles of the Past and Present, pp. 73-101. 



MOSASAURS 



Hutchinson, H. N., — Extinct Monsters and Creatures of Other Days, pp. 187-198. 



Lucas, F. A., — Animals of the Past, pp. 48-56. 



Osborn, H, F., — A Complete Mosasaur Skeleton: Am. Mus. Nat. Hist. Mem., 



Vol. 1, 1899, pp. 167-188. 

 Williston, S. W., — Water Reptiles of the Past and Present, pp. 148-167. 



General 



Chamberlin and Salisbury, — Geology, Vol. 3. 



Williston, S. W., — Water Reptiles of the Past and Present, pp. 59-72. 



Woodward, A. S., — Vertebrate Paleontology. 



Zittel-Eastman, — Textbook of Paleontology. 



Turtles. — It is an interesting fact that, although turtles are so 

 widely different from other forms at the present, yet, even when first 

 known, — in the Upper Triassic, — they are as typically turtle-like 

 as now. Jurassic turtles were abundant, had a world-wide distribu- 

 tion> and were closely related to existing genera. The first strictly 

 marine turtles (in which the feet are modified to form " flippers ") 

 have been found in the Cretaceous, one of which, Archelon, was of 

 great size, the head measuring three feet in length, the total length of 

 the animal being 12 to 14 feet. In this case, the shell proper had dis- 

 appeared, and the broadened ribs were possibly covered with a soft 

 skin, as in some living marine turtles (Dermochelys). Land turtles 

 did not appear until the Tertiary. 



A number of suggestions as to the origin of turtles have been offered, 

 but since the earliest known species are far from being generalized, 

 the whole matter is, as yet, in doubt. 



