R. S. Lull — New Tertiary Artio dactyls. 103 



developed inner lobe. Externally the anterior cnsp is 

 buttressed by a pronounced style corresponding to the 

 parastyle of the molars. There is, however, a less de- 

 cided ridge flanking the protocone than in D. borealis. 

 Comparison with D. americanus and D. antilopinus is im- 

 possible from lack of preservation of the tooth. 



P 3 is broader in proportion to its length and subtrian- 

 gular in outline. The protocone is well developed, but the 

 anterior cusp is relatively less pronounced, although well 

 buttressed. Here the deuterocone is present and the 

 inner crescent is no longer like a mere cingulum but is 

 better developed, although in a stage transitional between 

 that of P 2 and P 4 . There is practically no trace of a 

 cingulum such as that indicated by Douglass 8 in D. bo- 

 realis. In P 4 the transverse diameter exceeds the an- 

 teroposterior for the first time, the tooth being again 

 triangular with a well-rounded internal angle. The inter- 

 nal crescent forms about one third the bulk of the tooth, 

 but the deuterocone has practically merged into the 

 crescent, a faint ridge on the inner concave face of the 

 latter being its only indication. The outer crescent is 

 flanked by an anterior, median, and posterior style, the 

 last being the least conspicuous. P 2 is two-rooted, while 

 P 3 and P 4 are borne upon three each, in conformity with 

 their triangular shape. 



Upper molar teeth. — The three upper molars are some- 

 what similar. The first and second have accessory folds 

 on the adjacent ends of their inner crescents, on both in 

 M 1 , on the anterior crescent in M 2 . No trace of a cingulum 

 is present, but each tooth bears a very small internal cusp 

 lying between the bases of the inner crescents. This 

 varies in development in different individuals. Extern- 

 ally the parastyle and mesostyle are strongly developed, 

 as is also a buttress flanking the paracone. The outer 

 face of the posterior external crescent (metacone) shows 

 no such buttress. In Dromomeryx antilopinus (Scott) 

 the third premolar is the largest of the series, exceeding 

 P 4 in both dimensions, which is not true of the present 

 form, wherein P 4 has the greater transverse diameter and 

 area, although it is somewhat less than P 3 antero-poste- 

 riorly. The proportions of the molar teeth agree in the 

 two species, as do the para- and mesostyles. The same is 

 true of the median rib on the antero-external crescent 

 and of its obsolescence on the postero-external. Scott 



8 Op. cit., pi. LXIII, figs. 1, 6. 



