134 THE PERMO-CARBONIFEROUS RED BEDS OF 



ing-teeth upon the palate adapted to the mastication of insect larvae and 

 small crustaceans. A lateral position of the orbits is not necessarily indica- 

 tive of terrestrial life, as is shown by their position in the Plesiosaurs, Icthyo- 

 saurs, etc. However, far too little is as yet known of this New Mexican form 

 to warrant extended speculation on its habits or form. 



REPTILIA. 

 COTYLOSAURIA. 



Diadectcs (plate 20, fig. 3, a and b). — This genus is representative of a 

 considerable number of less well known forms which were probably similar in 

 habits and in the shape of the body. Bolbodon, Chilonyx, Diadectoides, Baihy- 

 glypliis {?), and Desmatodon were all diadectid animals, but any attempt at a 

 restoration of any one of these must await further discoveries. 



Diadectes probably reached an extreme length of 2.5 to 3 meters. Only 

 a few bones of the giant Diadectes maximus have been found, but that there 

 was such a creattire is known from vertebrae and limb bones. Diadectes 

 pliaseolinns, the best-known species, did not reach a length of more than 2 

 meters. The body was short and stout, with a tail equal in length to the rest 

 of the body. The limbs were extraordinarily heavy, and the humerus espe- 

 cially very broad, with powerful muscular articulations. The limbs ended 

 in wide, short feet, with stubby digits, terminating in broad nail-like claws. 

 The pectoral girdle was very strong, the bones being closely articulated, 

 but as a whole it was surprisingly narrow. From the spread of the ribs and 

 the general strength of the body, it might be expected that the fore-quarters 

 would be broad, but this is not the case; the fore-quarters were decidedly 

 narrow. The heav>' head, with its large, lateral eyes and large auditory open- 

 ings covered by a tympanic membrane, was set so close to the body that there 

 was apparently no neck. In restoring the skeleton of the animal, it was 

 found difficult to so arrange the bones that when the scapula was placed at 

 what seemed the most posterior point possible the angle of the lower jaws 

 would be free. The armor was confined to the anterior part of the thorax, 

 unless, indeed, there was a row of dermal plates upon the back, as suggested 

 above. 



It is impossible to escape the idea that the animal was a very efficient 

 excavator, and though Williston has shown that it would be impossible or 

 very inconvenient for it to excavate a burrow, it might still have made use 

 of its powers in procuring a food-supply of roots or burrowing animals. 



Diadectes was a sluggish, harmless creature, dependent upon its imper- 

 fect armor or upon concealment for protection. It moved with a sprawling 

 gait, the limbs standing well out from the body, which rested upon the ground. 

 There is no doubt that it could raise itself slightly from the ground, but it 

 was not possible for it to bring the limbs underneath the body, and walk 

 or run. As suggested previously by the author (Carnegie Inst. Wash. Pub. 

 145), it must have resembled to some degree the modern Ilelodcrma, especially 



