OPHIDIA. 103 



The only extinct genus with which it is necessary to compare the 

 present one, is the Boavus* of Marsh, which was described more than a 

 year previously. There are various points in which Professor Marsh's full 

 description con-esponds with my specimens, but I observe two important dif- 

 ferences: One is, that in Boavus the diapophyses are said to be "convex 

 throughout," while here they present a median constriction, giving a figure 

 eight outline. The other is, that the cup and ball are "more nearly verti- 

 cal" than in Boa; the ball is very oblique in Protagras. 



The modern affinities of Protagras will be fully considered in connection 

 with the Ophidia of the Miocene period in a later portion of the present work. 



But one species is known as yet. It was found in the Bridger beds 



of Wyoming. 



Protagras lacustris Cope. 



Paleontological Bulletin No. 3, 1872, p. 3. Proceed. Amer. Philos. Soc. loc. sup. cit. Annual Report 



U. S. Geol. Surv. Terrs., 1872 (1873), p. 632. 

 Plate XXUI, figs. 17-18. 



A serpent of about the size of the existing pine snake {Pityophis me- 

 lanoleucus). 



A vertebra before me has the longitudinal hypopophysial keel horizon- 

 tal, and terminating in a very obtuse point. The ball looks extensively 

 upwards. The upjDer articular extremity of the diapophysis is short and 

 obtuse, and the inferior equally so, and directed shortly downwards, their 

 articular surface being continuous with each other. It sends an obtuse 

 latero-inferior keel backward, which terminates distinctly in front of the 

 ball. Its inferior angle stands below the inferior margin of the articular 

 cup. The angle connecting the diapophysis and zygapophysis is strong, 



while the former is narrow. 



Measurements. 



M. 



Length of centrum with ball, below 0090 



Elevation behind, total 0135 



Elevation before, total - 0119 



Width between di.ipophyses, below 0055 



Width of articular cup 0054 



Depth of articular cup 0043 



Depth of inferior keel 0010 



Found by myself in the Bridger bad lands of Cottonwood Creek, 

 Wyoming. 



* American Journal Science and Arts, 1871, May. 



