0. C. Marsh — Notes on Mesozoic Vertebrate Fossils. 175 



The wear is in front of the apex, and on one side, sometimes 

 on both sides, as in. figure 6, Plate III. This tooth may be 

 taken as the type of a new species, Aublysodon cristatus. 



The fact that these peculiar teeth are apparently in pairs,, 

 and are in themselves more like the teeth of mammals than 

 of reptiles, has long been considered by the writer an argu- 

 ment for the mammalian character of the smaller forms 

 at least. The large crenulated teeth described by Leidy 

 strongly resemble those of carnivorous Dinosaurs, as he con- 

 sidered them, but no Dinosaur teeth of this form have been 

 found in position in the jaws. The next smaller size, with 

 very faint crenulations, one of which is figured in Plate III, 

 figure 5, is too large for any mammal yet known from the 

 Laramie, and this is true, also, of those figured by Leidy. 



Many of the smaller teeth of this type, if considered apart 

 from the others, would naturally be regarded as mammalian 

 incisors, especially from the lower jaw, and the wear of the 

 summits would in itself tend to strengthen this reference, if 

 some of these teeth alone were considered. A number have 

 been found, however, that show wear not only on the summit 

 and on one side near the summit, but also on the other edge. 

 This would imply, if these teeth are really lower incisors, 

 either that the rami of the lower jaw were so loosely united at 

 the symphysis that motion between them was possible, so that 

 the incisors could thus rub against each other, or that these 

 teeth were separated so as to admit the upper opposing teeth 

 between them. 



That some of these teeth are mammalian incisors there can 

 be but little doubt, and this doubt can only be removed 

 entirely by the fortunate discovery of a tooth in position in 

 the jaw. 



Cimolopteryx, Marsh, 1889. 



...The only bird hitherto known from the Laramie deposits is 

 Cimolopteryx rarus, the type specimen of which is represented 

 on Plate III, figure 2. Another species, about twice the size of 

 the first, is indicated by various remains, among them the cora- 

 coid._^ This bone lacks the strong inner process near the pit for 

 the scapula, which is characteristic of the smaller form. The 

 present species, which may be called Cimolopteryx retusus, i& 

 also from Wyoming. 



The new Laramie fossils here described and figured were 

 collected by Mr. J. B. Hatcher and party, in the Ceratops beds 

 of Montana and Wyoming. They will all be discussed more 

 fully in another communication. 



JTew Haven, Conn., July 18, 1892. 



