244 'Prof. 0. C. Marsh — American Jurassic Mammals. 



somewhat similar to that of a Eodent. This lower tooth has not heen 

 found in place, but the one represented in Plate VI. Figures 14 and' 

 15, may, with considerable probability, be referred to this position. 

 The remaining lower teeth have not been found associated with the 

 upper jaws, but they evidently resembled those of Ctenacodon, in 

 some of their most important characters. 



In comparing Allodon with Bolodon, we evidently have two nearly 

 related forms. So far as at present known, Allodon has three incisors 

 instead of two, a larger number of teeth in the premolar and molar 

 series, and likewise shows other differences of less importance. 



The affinities of these peculiar mammals and the inferences in 

 regard to their habits and food, which may be drawn from the 

 specimens now known, will be fully discussed by the writer else- 

 where. 



Allodon foktis, Marsh. 



The present species appears to be generically identical with the 

 type specimen of Allodon laticeps, but is represented by remains of 

 much larger size. The premaxillary shown on Plate YI. Figures 

 7-10, may be taken as the type specimen. A number of upper 

 molar teeth, and the large lower incisor (Figures 14 and 15 of the 

 same Plate), are also referred to this species. 



The first incisor in this premaxillary was very small, and situated, 

 close to the median line. It is wanting in the present specimen, but 

 its size and position are indicated in the above figures. The second 

 incisor is large and prominent, and is the principal front tooth. It 

 has a distinct crown, which is covered with enamel, and consists of 

 one large main cusp, with a small posterior cone. The lower surface 

 is much worn, evidently by an opposing lower tooth which bore 

 directly against it, from its apex to the small posterior prominence. 

 The sides of the crowns show no signs of wear. The third and last 

 incisor is much smaller, and is separated from the second by a short 

 diastema. It has a distinct crown covered with enamel, but shows 

 no marks of attrition. It is situated a little in advance of the suture 

 with the maxillary, shown in Figure 7, s, Plate VI. 



A second specimen referred to this species is shown in Figures 

 11-13, Plate VI. It is a portion of a left upper jaw containing 

 three premolars, apparently the first, second, and third. The first 

 two of these have a single external cone, and two inner cones, and 

 the second tooth is larger than the first. The third premolar is still 

 larger, unlike the corresponding tooth in Allodon laticeps, and has a. 

 second exterior cone behind the main one. Above this tooth, there 

 is a large cavity, apparently the entrance of the antorbital foramen. 

 This is shown in Figure 11,/, Plate VI. 



The large lower incisor which met the prominent one above is 

 probably represented in Figures 14 and 15. This tooth is faced with 

 enamel in front, and grew from a persistent pulp, like the incisor of 

 a Eodent. The summit is incomplete, and hence the shape of the 

 worn surface cannot be determined. 



The specimens here described indicate that Allodon fortis was the- 



