96 University of Kansas Geological Survey. 



pophysis of the axis. 16. The caudal vertebrae support chevron 

 bones. 17. The teeth possess no true roots." 



In 1877 Professor Owen 44 criticized these views of Cope, con- 

 tending that the supposed ophidian characters do not really ex- 

 ist in the Mosasauria, summing up his conclusions with the 

 statement that "The fossil evidences of the Mosasaurians hith- 

 erto made known do not yield a single character peculiar to and 

 characteristic of the ophidian order." He contended that the 

 Mosasaurs are aquatic Lacertilia, holding a position similar to 

 that of the pinnipeds among the true carnivora. 



In his reply to this paper Professor Cope 45 gave the following 

 characters as essential in the definition of the order, which he still 

 contends is valid : "1. The parietal bones are decurved on the 

 sides of the cranium, and are continuous with the alisphenoid and 

 prootic elements. 2. The opisthotic is largely developed, and 

 extends upwards and forwards to the walls of the brain-case. 

 3. A distinct element connects the squamosal with the parietal 

 bone above the opisthotic. 4. The teeth have no roots. 5. 

 There is no sacrum. 6. There is no sternum. 7. The bones of 

 the limbs possess no condylar articular surfaces. 



"Of the preceding seven characters, the decurvature of the 

 borders of the parietal bone at the margins, and their continuity 

 with the margins of the prootic bones, is of importance as a 

 character not found in the Lacertilia and universal among 

 Ophidia. The opisthotic has a greater development than in 

 lizards, where it does not reach the brain-case upward. In 

 the serpents, its contact with the brain-case is well known. 

 The existence of another element lying on the opisthotic, first 

 pointed out by Marsh, is an important character. The anterior 

 extremity of this bone enters into the side wall of the cranium 

 below the parietal, occupying much the position of the pterotic, 

 and resembling, even more than the opisthotic, the suspenso- 

 rium of the Ophidia. Should this be the true homology, the 

 affinity to the Ophidia is not strengthened ; and should it prove 



44. On the Kank and Affinities in the Reptilian Class of the Hosasauridae, Gervais, Quart. 

 Journ. Geol. Soc, 1S77, 6^2. 



45. Cope, E. D., Professor Owen on the Pythonomorpha, Bull. U. S. Geol. and Geogr. Surv. 

 Ters., iv, No. 1, Washington, 1S78, pp. 299-311. 



