FORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 



103 



serration number, markedly different cusp formula of Mi, and other 

 lesser differences show it to be markedly distinct. It differs even 

 more, but in somewhat different ways, from Paredypodus tardus. 

 The generic reference is very dubious. 



Measurements of the type other than those given above: Width 

 Ml, 1.4. 



Genus EUCOSMODON Matthew and Granger, 1921 



EUCOSMODON SPARSUS." new species 



Figure II 



Type. — U.S.N.M. no. 10113, part of lower incisor, with a small 

 adherent jaw fragment. Collected by A. C. Silberling. 



Horizon and locality. — Loc. 25, and referred specimens from Loc. 

 51 and the Silberling Quarry, Fort Union, Middle Paleocene horizon, 

 Crazy Mountain Field, Mont, 



Diagnosis. — Type incisor, maximum transverse diameter 4.0, mini- 

 mum 1.4 mm, ratio 2.86. 



FiGURK \\.—Eucosmodon sparsus, new species, U.S.N.M. no. 10113: Part of lower incisor and fragment of 

 jaw. External view and cross section at anterior end of incisor as preserved, with enamel band shown in 

 heavier outline. Four times natural size. 



Remarks. — This is an interesting form worthy of formal record 

 despite the imperfection of the material. Poor as this is, it fulfills 

 the practical requirements of demonstrating distinction from any 

 comparable species and ensuring that better specimens, when found, 

 can be securely determined as of this species.^" The occurrence of 

 three essentially similar specimens from three different localities and 

 horizons, but all within this field and all in the No. 2 beds, covering 

 a short span of time, also seems to demonstrate the validity and con- 

 siderable range of the species. 



U.S.N.M. no. 9861 is a broken incisor from the Silberling Quarry 

 and no. 9705 a similar specimen from Loc. 51. Their dimensions, 

 given below, agree closely with those of the type. 



In maximum diameter these teeth approach E. americanus primus 

 and are significantly smaller than other comparable species. In 

 minimum diameter they are somewhat less and in compression ratio 



<' Sparsus, scattered, from the dispersion of the scantly known remains of the species. 

 " Such specimens are almost surely included in the American Museum collection, but they are not yet 

 prepared, and in any event it is proper that types be from the older collection, as far as possible. 



119212—37 8 



