FORT UNIOX OF CRAZY MOUNTAIN FIELD, MOXT. 93 



Table 11. — Measurements of Ptilodus naontanus: Continuous variates 



Table 12. — Distributions of discontinuous variates: Ptilodus montanus 



Serrations P4 



13. 

 14. 

 15. 



.-8 



.19 



2 



External cusps Mi : 

 Internal cusps Mi : 



External cusps M2: 4 5 



Internal cusps M2 : 2 4 



Cusps P3:< 



External cusps P-* : 



--3H 

 _._5» 

 .lOH' 

 -__li 



...3 



--I/2 

 ---Vz 



5 1 



6 4 



Median cusps P'':^- * „ 



2 



f 9 . 7 



Internal cusps P*o,f^ ' o 



(t/.".::::::;-"" 



External cusps Mi:-^8 



Median cusps M' 



..1 



6>$ 



-V2 

 5% 

 ..2 



Median cusps M^: 3 4 



'3 2 



4 2 



Internal cusps M^ ; 



• In all the teeth with five cusps and in all but one with six, the cusps additional to four are evidently 

 anterior, but in one with six there is an extra anterior and an extra posterior cusp. The tooth with seven 

 cusps has two extra anterior cusps and one extra posterior. 



' That is, a slight bulging shelf, generally vaguely papillate, but without distinct cusps. 



The internal cusps of M^ are invariably sheared by P4 at the anterior 

 end and cannot be accurately counted in any specimen. Failure to 

 recognize this would lead one to believe the various stages of wear 

 typical of different species, if not genera. The outer cu.^ips of M^ are 

 also too obscure to count in the available specimens. 



Tliis species is abundant both in the Gidley and Silberling Quarries, 

 where its remains are among the commonest and are the best preserved 

 of all the fossil mammals. No significant difference can be observed 

 between the specimens from the two quarries, and the preceding data 

 are based on the combined sample from both. Two specimens surely 

 of this species were found at Loc. 50, and a broken P4 from Loc. 51 

 probably belongs to it. 



