12 A REVISION OF THE COTYLOSAURIA OF NORTH AMERICA 



Revised description (in addition to the characters given in the revised descrip- 

 tion of the order): 



1. Surface of the skull rugose or tuberculate. 



2. Pineal eye enormous. 



3. Occipital condyle flat or concave. 



4. A more or less complete armor of plates overlying the ribs. Perhaps a 



median row of plates overlying the neural spines. 



5. Anterior ribs, at least, expanded into wide plates. 



6. Body low and heavy; neck extremely short; limbs short and stout. 



7. Tail moderately long, with strong chevrons. 



It has been shown by the author (13) that the Diadectidee possess many of the 

 characters assigned by Cope to the family Otocaelides and the order Chelydosaurta, 

 and for this reason the Diadectidee were placed in the Chelydosauria, but as this has 

 been shown to be in contravention of the rules of nomenclature the assignment must 

 be altered. The Diadectidee is here referred to its proper place in the Cotylosauria 

 and many of the characters originally assigned to the Chelydosauria are used in the 

 description of the Cotylosauria and Diadectidee. As will be shown later, the order 

 Chelydosauria must be transferred to the Amphibia. Otocoelus, the type of the 

 order and the family, turns out to be an amphibian, while Conodectes, though evi- 

 dently a reptile, is so imperfect that it is impossible to make an accurate and suffi- 

 cient description, and is tentatively placed with Seymouria Broili. 



In this paper there are considered as members of the family Diadectidee: Dia- 

 dectes, Chilonyx, Bolbodon, Desmatodon, Diasparactus, and Diadectotdes. Empedias 

 is eliminated as an indeterminate form; it was separated from Diadectes on the char- 

 acter of the presence of canine teeth, but no specimen assigned to either genus by 

 Cope shows canine teeth. The teeth are mostly indicated in the region by empty 

 alveoli and it is impossible to determine whether the larger alveoli were occupied 

 by large canines or by large incisors. 



Genus DIADECTES Cope. 



DiadecUs G)pe, Proc. Am. Phil. Soc, vol. xvii, 1878, p. 505. (Also Pal. Bull. No. 29.) 



DieidecUs Cope, Proc. Am. Phil. Soc, vol. xxxiv, 1896, p. 441. 



Diadectes Cope, Proc. Am. Phil. Soc, vol. xxxv, 1896, pp. 131 and 133. 



Empedocles Cope, Proc Am. Phil. Soc, vol. xvii, 1878, pp. 516 and 529. (Also Pal. Bull. No. 29.) 



Empedocles Cope, Proc. Am. Phil. Soc, vol. xix, 1880, p. 45. 



Empedias Cope, Proc. Am. Phil. Soc, vol. xx, 1883, p. 634. 



Empedias Cope, Proc. Am. Phil. Soc, vol. xxxiv, 1896, p. 441. 



Empedias Cope, Proc. Am. Phil. Soc, vol. xxxv, 1896, p. 131. 



Type: A rough fragment of a left lower jaw with but two perfectly preserved 

 teeth and two broken ones; also fragments of indeterminate vertebrae. No. 4360 

 Am. Mus. Nat. Hist. Cope Coll. From Texas. 



Original description: "Teeth with short and much compressed crowns whose 

 long axis is transverse to that of the jaws. Edges of the crown obtuse, with tuberos- 

 ities on some of them, distinct from the principal apex. The latter is worn off very 

 obliquely by attrition in all of the specimens. The crowns covered with an enamel- 

 like substance which has no especial sculpture. Alveoli not separated. The 

 external alveolar border in each jaw more elevated than the internal, and in the 

 superior series, at least, diverges from the tooth line backwards and outwards. The 

 surface of attrition descends outwards in the maxillary series, and rises inwardly in 

 the dentary series. A large fossa pierces the inner alveolar border just behind the 

 inner extremity of each tooth. 



