I4IO CLASS MAMMALIA. 



depth, and the lower molars with transverse ridges ; both the first 

 and second lower incisors being scalpriform, and growing from 

 persistent pulps ; and the genus may be regarded as connecting 

 Anchippodus with Calamodon. The lower dental formula appears 

 to be I. 2, C. i, Pm. 3, M. 3 ; and two species are known from 

 the Puerco, or lowest. Eocene of New Mexico. 



Family CALAMODONTiDiE. — In Ca/amodon, the type genus of 

 this family (the Tseniodontia of Professor Cope), the lower jaw 

 resembles that of Psittacotherium ; there are three lower incisors, 

 of which the second and third are scalpriform, and have their 

 anterior surfaces faced with enamel ; and the cheek-teeth are five 

 in number, but cannot be differentiated into premolars and true 

 molars. There is no diastema, and the cheek-teeth approximate 

 to those of the Rodents in their massive squared crowns, and have 

 also been considered to show resemblances to those of the Eden- 

 tates. The second lower incisor is much larger than either of the 

 others, and the mandibular condyle is transversely elongated. Pro- 

 fessor Cope, as will be noticed below, regards this group, and more 

 especially Psittacotherium, as close to the ancestral types of the 

 Rodentia, and has also suggested their alliance to the ancestors 

 of the Edentates ; Calamodo?i is from the Wasatch or Middle 

 Eocene. 



Family Stylinodontid^. — Professor Marsh has proposed this 

 family name for the North American Tertiary genus Styiinodon, 

 in which the molars grew from persistent pulps like those of the 

 Edentates. 



