0. C. Marsh — Discovery of Cretaceous Mammalia. 255 



figure 4. A number of separate incisors and molar teeth, 

 some with pieces of the jaw attached, were found at the same 

 locality, and one of the molars is represented on the same 

 plate, figure 6. The incisor in the type is much compressed, 

 and has its inner face concave. The symphysis of the jaw is 

 very small, and situated on a distinct elevation. The molar 

 tooth shown in figure 6 is from the lower series, and apparently 

 the penultimate. The cusps are tubercular, and there is a deep 

 median groove between the two rows. 



This species is about half the size of Cimolodon nitidus, a 

 molar of which is shown on the same plate, figure 7, and a 

 lower jaw, in figure 9. The latter specimen is of special 

 interest, as it shows the smooth fourth premolar in place, with 

 the summit of the crown on a level with the two molar teeth 

 behind it. 



These specimens are all from the Laramie of Wyoming. 



Cimolodon agilis, sp. nov. 



The smallest species of this genus is represented by various 

 remains, the most important of which is the left lower jaw, 

 shown on Plate VI, figure 8, which is here taken as the type 

 specimen. The penultimate molar is in place, and its position 

 is so far back that its posterior margin is opposite the front of 

 the coronoid process. The last molar, when present, was 

 entirely concealed by this process when seen from the outside. 

 The molar preserved has the two rows of tubercles close 

 together, with only a valley between them. 



This specimen, which belonged to an animal the size of a 

 mouse, was also found in the Laramie deposits of Wyoming. 



Allacodon fortis, sp. nov. 



Since the genus Allacodon was established by the writer, in 

 Part II, many additional specimens have been secured, so that 

 the entire upper series of molars and premolars, at least, is 

 believed to be known. Of these teeth, there are three distinct 

 sizes, representing as many species. The largest of these is 

 undescribed, and the tooth shown in Plate VII, figure 4, 

 one of the most characteristic, may be taken as the type. 

 It is evidently an upper premolar corresponding to the middle 

 one in the jaw of Allacodon pumilus represented on the same 

 plate, figure 3. 



The upper teeth in this genus, besides those figured, have 

 either five or six cones on the crown, and are evidently molars, 

 showing that this genus is closely allied to Allodon of the 

 Jurassic, described by the writer. 



