DOUGLASS: THE TERTIARY OF MONTANA 223 
MEASUREMENYS OF SPECIES OF Icrops. 
z 5 eebes 2 : 3 5 
& 3 3 ; Ss 5 : Ss 2 
34 24 S¢ Sq Sa ad 34 
SA $48 34 ae SE} sq 2 | 
= BS S) ¢ s 3 eas 
a N | a Ni Ni 
Length of skull back of P+.. 48.5 45 | 
Width of skull at P2 8 7.6 
Width of skull at post-orbital constriction..... 13 | al 16 
Wiclthvoigocciputeesscsssencccssscesercssnceseeetes 20 18 
Width of occipital condyles 15 13 
Width of palate at P2.......... 5.5 6 6.5 
Width of skull at front of glenoid surface..... 25 ene 33 
Length of molar-premolar series.................. 23 22 28 
Length of premolar series.......... Ren 15.5 I) BIL 
Length of molar series .................sec0e08 eeeee 7.5 6.5 ze 10 
Length of molars and P2 and # .................. 14 | 1 14 18 9.3 
TECHS Oe JE. coosooon .coocossoadesc50000606 acts 1.3 2 
ILA Oi LP cocoossooneconqcodosadencda sosc0cdBoNE0n0 2.1 2.8 
Length of P® refinncoeeir ean eneeen mars 3.5 2.5 3.8 3.5 5 
Weng t hypoth seesdiess steers 3 2.2 3.1 3.3 3.8 
Width of P4 2.8 3.3 | 2.9 3.3 3.4 
Length of M+ 2.5 2.2 2.2 3 3.6 Qu 3.3 
Width of M1. .............. 3.5 3.5 4.2 38 4.3 3.9 4 
Length of M2 2.2 2.2 2.2 2.2 3.5 
Width of M2............ 3.8 4 4 4.2 5 
Length of M2 2 9) 1.5 2 1.5 
Wild the ofa Mis ii aesne oan centieserctneceesiiecstineneee 33 3 3 4 3.6 
Depth of mandible under M,j .... wake 5 | 5.2 4.5 5.7 
Length of lower dental series .... 2h ; 29 32 
Length of lower molar series... Baca 7 | 8.5 10 
Weng thot esscecwsacscsests one shececesesossscnscenes 2.5 | 2.5 4 
Length of M,..... sein apt aaa) Shite 2.5 3.2 
Hen othyotetemuresenccesssescoasseete tect ee eet | 45 
1 According to Matthew, J. dakotensis measured from Leidy’s figure. 
In width of molars in relation to length: (1) /. tenwis, widest in proportion to 
length, (2) L. intermedius, I. thompsoni, (3) I. montanus, (4) I. major, [. acutidens. 
In development of cingulum on cheek teeth: (1) L. intermedius? least, (2) I. 
tenuis, (3) L. montanus, I. acutidens, I. major. 
In robustness of zygomatic arch: (1) L acutidens least, (2) L. intermedius, (3) I. 
tenwis, (4) L. montanus. 
From what I have seen of the Leptictidee of the Oreodon horizon I think that in 
all these species from the Titanotherium beds of Montana, unless it be L. major, 
the teeth are proportionately smaller. 
