CHEWNIA 



239 



a height of one or two inches, and thus gave to the niid-hne of the 

 carapace, when seen laterally, a distinctly sinuous outline not 

 unlike that of Toxochelys.'^ 



As regards the habits of these ancient sea-turtles, we ma>' ulTer 

 tolerably certain conjectures. In the opinion of the writer, the less 

 reduced plastron indicates a bottom-feeding habit, a view that is 

 strengthened by the more rounded form of the shell, like that 

 of the river turtle. All in all it would seem that Protoslega and 

 Archelon lived habitually on the soft bottoms of the shallower seas, 

 feeding upon the hordes of large shell-fish, for which their powerful 

 parrot-hke beak was admirably adapted. That the species of Prolo- 

 stega did not commonly frequent the deeper oceans is indicated by 

 the general absence of their remains in the deeper water deposits. 

 The writer, in a long collecting experience, always found their 

 remains associated with those of the smaller Toxochelys, toothed 

 birds, pterodactyls, and the smaller mosasaurs. 



Perhaps no one can speak more authoritatively as to the habits 

 of these gigantic sea-turtles of the Cretaceous than Dr. Wieland: 



''With regard to the general habits and appearance of Archelon 

 much might doubtless be said if the present-day sea-turtles were 

 more familiar objects. Dr. Hay thought that Archelon ischyros 

 was a clumsy or even a sluggish, mainly littoral animal, moving 

 slowly about the bottom of quiet inlets in quest of shell-fish; I, on 

 the contrary, much struck by the powerful flippers, and especially 

 by the flattening of the humerus, with its low radial crest and obvi- 

 ously strong musculature, have held that unusual swimming power 

 and adaptation to a strictly marine life were indicated. Perhaps, 

 as usual where experts differ, it is probable that both views are in 

 part correct, and that Archelon was only a moderately good swim- 

 mer. It may be noted that, notwithstanding the almost circular 

 body, the femoral notch, that for the hind leg, lies far back, so that it 

 is not necessary, on the score of bulk, to assume slowness of motion, 

 or the inability to pursue a sea-going life. Furthermore, it is now 

 known that the development of the digits fell httle short of that 

 seen in Colpochelys (Fig. 117) or Eretmochelys, truly marine turtles. 



''Therefore, while there can be no doubt that Archelon was 

 strictly carnivorous in habit, and well able to navigate the open 



