NORTH AMERICA AND THEIR VERTEBRATE FAUNA. 135 



if the claws of that Hzard were made more nail-hke, and the tail more slender 

 and compressed vertically. It probably lived on the banks of streams, or in 

 the thick vegetation, seeking its food along water-courses or in damp spots, 

 and finding the vegetation a protection against the larger carnivorous reptiles. 

 The large eyes and the enormous, probably functional, pineal eye have led 

 to the suggestion that it may have been crepuscular in habit, with consider- 

 able powers of nocturnal vision, and came from its place of concealment only 

 when the shades of evening were dense enough to protect it. 



The more the author studies the anatomy and probable habits of this 

 creature, the more he is impressed with the probability of his previous sug- 

 gestion that it was in many respects similar to the modern swamp and land 

 turtles. 



Diadectoides was almost a travesty upon Diadectes. All the features of 

 strength and stoutness were exaggerated to a great degree. Its specific name, 

 cretin, was suggested by the dwarfish, overpowerful appearance of the imper- 

 fect skeleton. 



Chilonyx had begun to develop a tuberculate condition of the skull like 

 that of the Pariesaurus of Russia or Elginia of the Scottish Trias. Bathy- 

 glyptus apparently was of the same type, but is so little known that no sug- 

 gestion as to its size or form can be hazarded. 



Animasauras and Diasparactus. — These animals from the New Mexican 

 deposits were probably very similar to Diadectes in external form. Only the 

 skull of Animasauras is known. The exact form of the teeth has not been 

 made out in either, but the shape of the roots shows that they were similar 

 to those of Diadectes in a general way, and so indicate similar habits and food- 

 supply. They took the place in the New Mexican region that Diadectes 

 occupied in Texas. The possibility that Diasparactus was more primitive 

 than Diadectes is suggested by the fact that it has longer dorsal spines, with 

 no indication of a possible dermal armor of ossicles. 



Limnoscelis (fig. 20). — This animal shows relations both to Diadectes and 

 Labidosaurus, as suggested by Williston. The form of the body and the 

 stout limbs were like those of Diadectes, but the shape of the head, the posi- 

 tion of the orbits and nares, the small pineal foramen, and the dentition 

 composed of conical teeth, with enlarged incisors in the upper jaw, are decidedly 

 reminiscent of Labidosaurus. As shown above, in the discussion of the food 

 habits and the aquatic adaptations, the animal was a dweller in the water. 

 Perhaps it was an aquatic branch of the same stem from which the terrestrial 

 diadectids rose. The structure of the vertebral column, the limb bones, and 

 the girdles are so similar in the two that we can not doubt that they had a 

 common ancestry. The modifications in the head, dentition, and feet are all 

 directly attributable to the adoption of an aquatic habitat. 



The animal was about the same size as Diadectes phaseolinus, or a good- 

 sized Eryops, and resembled the latter in habits mvich more than the former. 

 The broad paddle-feet enabled it to swim rapidly and easily, and it could lie 



