12 



17. Scotophilia noctivagans H. All. Silvery-haired Bat. 

 One specimen was taken at our camp of August 29, on the Big 



Porcupine. 



18. Vespertilio subulatus Say. Little Brown Bat. 



A specimen was taken at the mouth of the Little Porcupine, Sept. 

 1. A small bat of probably this species was more or less frequent at 

 most of our camps along the Yellowstone and Musselshell Rivers. 



murid^:. 



19. Mus musculus Linn. House Mouse. 



A specimen was taken in our camp at Foi't A. Lincoln, where the 

 species was already becoming common, although the post had been 

 established but one year. 



20. Hesperomys leucopus var. sonoriensis Coues, Ms. 

 White-footed Mouse. 



A specimen was taken at the Big Bend of the Musselshell, and 

 another on Heart River, and it undoubtedly occurs with greater or 

 less frequency along all the principal streams. 



21. Neotoma cinerea Bd. Mountain Rat. 



More or less frequent along the timbered portions of the streams. 



22. Arvieola riparius Ord. Meadow Mouse. 



A specimen was collected near the head of Heart River by Dr. W. 

 J. Hoffman, and by him kindly presented to the collection. Signs of 

 their presence were observed at various localities, but no other specie 

 mens were obtained. 



SACCOMYlim 



23. Dipodomys Ordii Woodh. Jumping Rat. 



The most abundant mammal met with in the valley of the Yellow- 

 stone; much less common on the Great Porcupine Creek and in the 

 valley of the Musselshell. It seems to prefer the dryest situations, 

 burrowing beneath the cacti and in bunches of sage brush every- 

 where. Rarely seen abroad, but occasionally surprised and killed by 

 the teamsters and soldiers, the collection being indebted to the kind- 

 ness of Dr. HoS'man for several specimens thus obtained. These 

 animals form little paths or " run ways " leading in various directions 

 from their burrows, not unlike those made by muskrats. 



24. Perognathus flavus Baird. Pouched Mouse. 

 Apparently common. First met with at the Big Muddy, and after- 

 wards along the Yellowstone and Musselshell. 



