ERYOPS. 191 



R. 574 y. The distal half of a femur ; from Texas. This specimen 

 accords in contour with the much larger femur of Eryops 

 figured by Cope in the ' Proc. Amer. Phil. Soc' vol. xix. 

 pi. iv. figs. 15, 16, 19, being nearly of the same absolute 

 size as the figure. Purchased, 1885. 



Family Position Uncertain - . 

 Rhytidosteus differs from the typical Archegosauridw in the 

 absence of large palatal vacuities, and thereby approximates to the 

 Anihracosauridaz and Nyraniidce, and also agrees with the latter in 

 the presence of denticules on the palate. The presence of denti- 

 cules on the mandible appears to connect Rhytidosteus with Eryops, 

 and if the latter had a closed palate of similar type the family 

 name Eryopidce, proposed by Cope, should be adopted for this group. 



Genus ERYOPS, Cope >. 



Syn. Rhachitomus, Cope 2 . 

 Epicordylus, Cope 3 . 

 Parioxys, Cope 4 . 



Skull 5 vaulted, comparatively short and wide, with large 

 postero-lateral expansions, the round and rather small orbits in 

 the posterior half, the nares ovoid, widely separated, and placed 

 some distance behind the extremity of the broad and blunt muzzle, 

 and the occipital condyles ossified. Mandible with alveolar parapet, 

 but without postarticular process. Teeth subconical and pointed ; 

 anterior ones enlarged; hinder ones small; minute denticules on 

 the mandibular ramus internally to the alveoli ; probably similar 

 denticules on the palate ; upper teeth in a single row. Cranial 

 sculpture coarsely pitted and ridged. The synonymy is taken from 

 Cope, ' Trans. Amer. Phil. Soc' vol. xvi. p. 286. 



Eryops megacephalus, Cope 6 . 



Syn. Rhachitomus valens, Cope 7 . 



The type species ; of very large size. Skull with the length in 

 the median line equal to the width, the muzzle very broad and 

 blunt, and the orbits forming the most prominent point in the 

 profile ; extreme length about 0,575 (22*5 inches), length in median 

 line about 0,465 (18-3 inches). 



Hab. North America (Texas). 



1 Proc. Amer. Phil. Soc. vol. xvii. p. 188 (1877). 2 Ibid. p. 520 (1878). 



8 Ibid. p. 515 (1878). 4 Ibid. p. 521 (1878). 



5 See Amer. Nat. vol. xviii. pp. 84, o~), figs. 5, 6. 



G Proc. Amer. Phil. Soc. vol. xvii. p. 188 (1877). T Ibid. p. 526 (1878). 



