APPENDIX. 



Art. XI. — Discovery of C? i etaceous Mammalia; by Professor 

 0. C. Marsh. (With Plates II, III, IV, and V.) 



It has long been a reproach to paleontology that no remains 

 of mammals were known from the Cretaceous formation, 

 which almost everywhere contains abundant evidence of other 

 vertebrate life. In the Jurassic below, many small mammals 

 have been found, both in Europe and America, and in the Ter- 

 tiary above, this class was dominant, and even at the base of 

 the formation is represented by many and varied forms. 



A comparison of the mammals known from the Jurassic and 

 the Tertiary made it almost certain that many intermediate forms 

 must exist in the Cretaceous, and their discovery was one of 

 the prizes held out to explorers. For many years, therefore, 

 special search has been made in various countries for Creta- 

 ceous mammals, but thus far, almost invariably without success. 



The most promising field for discovery was evidently in the 

 Rocky Mountain region, and the first announcement was made 

 in 1856, when Leidy described as mammalian, under the name 

 Ischyrotherium antiquum, certain vertebrae found by Hayden 

 in the Judith basin, Montana.* It is now known that these 

 remains, as Leidy himself suspected, are reptilian, and the 

 generic name has been changed by Cope, to Ischyrosaur%is.\ 



* Proceedings Philadelphia Academy, vol. vii, p. 89. See also, Transactions 

 American Philosophical Society, 1859, p. 150. 



f Synopsis of Extinct Batrachia, Reptilia, etc., p. 38, 1869. 



