Plate VI. 



(About natural size.) 



Figs. 1 and 2. Cynomys ludovicianus ludovicianus (Ord). ad. Mason, Texas. 



(No. 191388, U. S. Nat. Mus.) 

 Figs, 3 and 4. Cynomys ludovicianus ludovicianus (Ord). c? ad. Mason, Texas. 



(No. 191389, U. S. Nat. Mus.) 



Selected skulls of same sex and age from one locality ; to show the great individual 

 variation frequently noted in skulls of Cynomys. 



