CONDYLAETHKA. 



387 



The geological distribution of the nine genera of these families is as 

 follows : 



Haploconu8.. 

 HemithljBus 

 Anisonchus .. 

 Periptychns 



Protogonia . . 

 Anacodon . . 

 Phenacodns 

 Diacodexis . . 



Men iscotherium 



PeriptychidcB, 



Phenacodontidce. 



Meniteotheriidce. 



Puerco. 



17 



Wasatch. 



11 



PERIPTYCHUS Cope. 



American Naturalist, 1881, p. 337 (March); Catathlmus, Cope, American Naturalist, 1881, 829, Sept. 22. 

 Proceeds. American Philosoph. Soc, 1881, p. 487. 



Dental formula: I. 



2or3 



1 



C. -; Pm. -; M. -. Premolars of superior 



jj ' - 1' -— 4' —3 

 series consisting of external conic cusp, and an internal crescentic crest, 

 which is like a developed cingulum surrounding the cusp. Crowns of true 

 molars supporting seven tubercles, as follows: two external; one principal 

 median internal, which has accessory cusps, one anterior and one pos- 

 terior to it; lastly, two, an anterior and a posterior intermediate tubercles. 

 Diastemata in both series small. Inferior incisors small; canines of mod- 

 erate size. Inferior premolars consisting of one principal external cusp, and 

 an internal cingulum. This rises medially into an accessory cusp, and 

 , extends posteriorly into a narrow heel, and anteriorly into a small anterior 

 basal tubercle. The inferior true molars sustain four principal cusps op- 

 posite in pairs, with accessory median ones on the anterior and posterior 

 borders. The posterior median lobe is so developed in the last inferior 

 molar as to constitute a fifth lobe or heel. 



