ART. XIV.-PROFESSOR OWEN ON THE PYTHONOMORPHA. 



By E. D. Cope. 



The British Museum has recently obtained the Van Breda collection 

 of fossils, which includes a valuable series of Mosasauroid remains from 

 Maestricbt, the locality which furnished to Cuvier the typical specimen 

 of the Mosasaurus giganteus. Professor Owen has improved the oppor- 

 tunity to study this material with that already in possession of the 

 museum, some of which was derived from North American sources. 



In pursuing this subject, Professor Owen has done me the honor to 

 study my contributions to it, a summary of which appears in the second 

 volume of the Final Eeport of the United States Geological Survey of 

 the Territories under Dr. F. V. Hayden. He follows my determinations 

 and conclusions, and criticises them in the light of his long experience. 

 As a portion of this criticism is adverse to what he supposes my conclu- 

 sions to be, I propose on the present occasion to give such a brief review 

 of Professor Owen's paper* as my other immediate occupations will 

 permit. I premise that this cannot now include a complete review of 

 the subject, nor the exposition of several parts of it which have not yet 

 received the attention of Professor Owen or of any one else. 



Professor Owen's references to my work may be included under three 

 heads, viz : — First, as to matters of fact or observation ; second, as to de- 

 termination of homologies of parts ; third, as to the estimation of affini- 

 ties as derived from the preceding branches of the subject. I now con- 

 sider — 



I.— QUESTIONS OE FACT. 



The many observations as to the structure of the order of Pi/tJiono- 

 morpha recorded by me in the volume already referred to are confirmed 

 by Professor Owen with a single exception. He correctly describes the 

 vertebrae of the genus Mosasaurus as withont the zygantrum and zygo- 

 sphene articulation, and proceeds to say (p. 709), in reference to mj' 

 ascription of this structure to the genus Clidastes, that the structure 

 of Mosasaurus "is repeated in plates xviii, xix, xx, xxi, xxiii, xxiv, xxvi, 

 xxvii, xxix, XXX, xxxiv, and xxxvof Professor Cope's great work; in every 

 figure thezygospheneand zygantrum are absent." And again, — ''In the 

 plates xviii and xxiii given to the vertebrae of the species [Clidastes] 

 stenops and planifrons, the parts and processes are as usual not indicated." 

 All this is a remarkable oversight on the part of Professor Owen. He 

 ^Quarterly Jourual of Geokgical Society, London, 1^77, p. GS2. 



