20 A REVISION OF THE COTYLOSAURIA OF NORTH AMERICA 



In the "Proceedings of the American Philosophical Society" for 1883 the name 

 Empedias is used, as Empedocles was found to be preoccupied. In this paper Cope 

 gives additional characters of the species: 



"The species of Empedias forms a series which differs from Diadectes in a 

 successive widening of the crowns of the teeth and diminution in number. Thus 

 the E. (written D.) phaseolinus is nearest to the Diadectes; E. (written D.) molaris 

 succeeds it, and in E. fissus we have the molariform character most strongly de- 

 veloped. In the E. latibuccatus, on the other hand, the diminution of the transverse 

 extent of many of the teeth and the areolar sculpture of the superior surface of the 

 cranium points in the direction of the genus Chilonyx. The species of Empedias 

 may easily be distinguished as follows: 



"I. Surface of the skull divided by grooves into area?. 



Superior teeth, 16 on each side, a number on each end of the maxillary bone of little trans- 

 verse extent E. latibuccatus 



II. Surface of the skull uniformly rugose. 



Superior teeth narrower, 16 on each side, the last one small, sphenoid flat, pterygoids 



narrow E. phaseolinus 



Superior teeth wider, 14 on each side, the last one smaller, the sphenoid keeled medially, 



pterygoids wide E. molaris 



Superior teeth wider, 14 on each side, the last the largest, sphenoid not keeled . . E. fissus." 



In 1896 the genera of the Diadectidce were redefined and the E. latibuccatus 

 with the species phaseolinus was restored to the genus Diadectes. 



Revised description: It is admittedly dangerous to form species in vertebrate 

 paleontology, and especially is this true when dealing with such distorted material 

 as occurs in the beds of Texas, where almost every specimen could be described as a 

 new species — or with a little more latitude almost every specimen of a genus could be 

 retained in a single species. The teeth are more apt to present determinable charac- 

 ters and the foregoing discriminations have been based entirely upon them. In 

 the type specimen of D. latibuccatus only the bases of the teeth are preserved and in 

 the second specimen used by Cope in his descriptions, No. 4353 Am. Mus. Nat. 

 Hist. Cope Coll., but a single one near the posterior end of the series has any portion 

 of the crown preserved. This tooth looks something like those of D. biculminatus, 

 but it is very uncertain. The larger number of teeth, seventeen, in the maxillary, 

 and the more numerous smaller teeth with nearly round section at the base, in the 

 region of the maxillary-premaxillary suture, are the only distinguishing characters. 



Diadectes maximus Case. 

 Bull. Am. Mus. Nat. Hist., vol. xxvm, art. xvu, 1910, p. 174. 



Type: Three large vertebrae. No. 4392 Am. Mus. Nat. Hist. Cope Coll. 

 From Texas. 



A large number of isolated bones in different collections indicate the presence 

 of a very large member of the genus Diadectes. Size alone, however, is not sufficient 

 to indicate specific difference in the reptilia where growth is practically continuous 

 through life. These vertebrae, from the posterior portion of the column, show 

 a distinct difference from the other members of the genus in the position of the 

 hyposphene and hypantrum. The faces are nearly horizontal instead of being 

 sharply oblique. 



Measurements. mrn 



Distance from bottom of posterior face of centrum to base of spine . . . 1465 



Height of the posterior face of the centrum 5^-5 



Length of bottom of centrum 4-8 



Width across posterior zygapophyses 14° 



