Plate VI T. 



(About natural size.) 



Fig. 1. Cynomys ludovicianus ludovicianus (Ord), left mandibular ramus. 9 ad. 

 Glendive, Montana. (No. 191407, U. S. Nat. Mus.) 



Fig. 2. Cynomys mexicanus Merriam, left mandibular ramus. $ ad. La Ventura, 

 Coahuila, Mexico. (No. 79554, U. S. Nat. Mus., Biological Survey collection.) 



Fig. 3. Cynomys ^wnmsomg'itnmsom* (Baird), left mandibular ramus, c? ad. Sagua- 

 che, Colorado. (No. 176695, U. S. Nat. Mus., Biological Survey collection.) 



Fig. 4. Cynomys parvidens Allen. $. ad. Buckskin Valley, Utah. (No. 158994, 

 U. S. Nat. Mus., Biological Survey collection.) 



Fig. 5. Cynomys leucurus Merriam. c? ad. Cumberland, Wyoming. (No. 179515, 

 U. S. Nat. Mus., Biological Survey collection.) 



Fig. 6. Cynomys gunnisoni gunnisoni (Baird). c? ad. Saguache, Colorado. (No. 

 176695, U. S. Nat. Mus., Biological Survey collection.) 



Figs. 7 and 8. Cynomys ludovicianus ludovicianus (Ord). $ juv., showing milk pre- 

 molars and unworn crowns of molars. Ishawooa, Wyoming. (No. 169674, 

 U, S. Nat. Mus., Biological Survey collection.) 



