180 University of California Publications in Geology [Vol.10 



The new genera are based largely on the characters of the teeth, 

 particularly on differences in the enamel patterns, but, where parts 

 of the skeleton are known, decided differences from other lagomorphs 

 are found also. 



The material on which the following descriptions are based is 

 located in the Palaeontological Collections of the University of Cali- 

 fornia. Thanks are due Dr. J. C. Merriam for advice and criticism 

 during the progress of the study. The drawings of the teeth have 

 been made with a camera lucida on a microscope magnifying twelve 

 diameters, and the pattern of each tooth has been drawn separately, 

 from a point of view parallel to the length of the tooth. 



ARCHAEOLAGUS,i new genus 



Type species Lepus ennisianus Cope 



Abundant in the Upper Oligocene John Day beds of Oregon. Be- 

 sides the descriptions- and figures 3 given by Cope there have been 

 available in this study a considerable number of specimens from the 

 John Day beds now in the palaeontological collections of the University 

 of California. 



Fig. 1. Archaeolagus ennisianus (Cope). Left upper molariform teeth, X 3. 

 Univ. Calif. Coll. Vert. Palae. no. 1501. John Day beds, Oregon. 



P= with a shallow groove on its anterior face. Upper molariform 

 teeth with interior re-entrant angles not crenated and not extending 

 as far as half across the crowns. On these teeth there are often enamel 

 crescents exterior to the outer ends of the re-entrant angles, and some- 

 times the backs of the crescents connect with the outer side of the 

 teeth. P,: shows an exterior re-entrant angle extending about half way 

 across the tooth. Anterior to this is a shallow groove, which is also 

 on the outer surface. The inner border of the tooth is without re- 

 entrant angles, differing in this respect from Palaeolagus. Mj is im- 

 perfectly divided into two columns by a deep exterior re-entrant angle. 

 There is very little cement on any of the teeth. 



1 dpx a "> s i primitive; \ayQs, hare. 



2 Cope, E. D., Bull. U. S. Geol. Sur. Terr., vol. 6, pp. 385-386 (1882). 



s Cope, E. D., Tertiary vertebrata, Rept. U. S. Geol. Surv. Terr., vol. 3, bk. 1, 

 pi. 64, figs. 11 and 11a; pi. 66, figs. 29a, 29&, and 29c (1884). 



