82 0. C. Marsh — Cretaceous Mammalia. 



A second announcement was made by Cope, in 1882, based 

 upon a few fragmentary remains discovered by Dr. J. L. Wort- 

 mann, in Dakota. These fossils, although not found in place, 

 were apparently from the Laramie formation. The name 

 M< niscoessus conquistus was given by Cope to two of these 

 specimens.* One of them was considered a premolar, and first 

 described. The second was an imperfect molar tooth. A third 

 specimen, the distal end of a humerus, was thought to represent 

 a second smaller species, indeterminable. These three specimens 

 were figured by Cope, in 1884. f 



It is now known that the tooth first described, and regarded 

 as a premolar, is the tooth of a Dinosaurian reptile, as sug- 

 gested by Cope, and not of a mammal. The name given, 

 therefore, must apply to this alone. On this point, the rules of 

 nomenclature are clear and decisive. The imperfect molar 

 tooth, subsequently described, and the fragment of a humerus, 

 are evidently mammalian, but without a name. 



The writer has made a careful search for Cretaceous mammals 

 in various parts of the West, both personally, and through par- 

 ties under his direction. Last season, a special exploration was 

 made in the Laramie formation^ of Dakota and Montana, but 

 without the expected success. I This spring, a renewed search, 

 and more systematic investigation, were undertaken in the same 

 formation, in Dakota and Wyoming, and the results already 

 attained have furnished the material for a new chapter in pale- 

 ontology. Mr. J. B. Hatcher, the writer's valued assistant, had 

 entire charge of the field work, and to him belongs the main 

 credit of the fortunate discoveries made. 



These discoveries consist, in part, of not less than one 

 hundred specimens of mammalian remains, including jaws, 

 teeth, and various portions of the skeleton, most of them in 

 good preservation. They represent many individuals, all of 

 small size, and not a few new genera and species. Some of 

 the more important of these are described below, and others 

 will be noticed in a later communication. 



LThe remains here described were found in the typical Lar- 

 amie formation, either in place, or in association with other 

 fossils that determine their geological position beyond reasona- 

 ble doubt. The vertebrate fossils found with them are mainly 

 the remains of Dinosaurs, which are represented by at least two 

 orders, and several families. The most abundant specimens are 

 teeth of carnivorous forms allied to Megalosaurus, others of 

 Uadrosaurus and its allies, and two or more species of 

 Ceratops. The kind of tooth described as Meniscoessus is not 



* American Naturalist, vol. xvi, p. 830, 1882. f Ibid., vol. xviii, p. 693, 1884. 



