498 
U. S. P. R. R. EXP. AND SURVEYS—ZOOLOGY-GENERAL REPORT. 
The specimens agree in all essential characters of color and proportions—No. 87 only 
having a greater admixture of yellowish rusty on the sides, and a still longer tail. 
The skull of this species differs from all those with slender tails in the greater elongation of 
the nasal hones, and consequently longer snout. The outline of the skull above, from the 
parietals to the middle of the nasals, is perfectly plane, or even slightly concave ; the interval 
between the orbits very narrow and the outlines concave. The bone between the parietals and 
occipital is narrower anteriorly than in other species and advances further forward between the 
parietals. 
This species was described by Audubon and Bachman as N. drummondii, but the possession 
of a specimen of very different character, collected east of the Kocky mountains by Dr. Suckley, 
and which seems to be a fair representative of the last mentioned species, enables me to separate 
the two. The fur of N. occidentalis is much coarser and crisper, without the soft, compact 
feeling of N. cinerea. The ears are perhaps smaller. The tail is longer, with more plum¬ 
beous above and less white laterally. The back is much darker, though mixed with yellowish 
brown. For other differences, I would refer to the article on N. drummondii. It is probable 
that the present species is confined to the country west of the mountains, or even near the 
Pacific coast; N. cinerea occurring in the main chain, or east of it. 
The bone caves of Pennsylvania have furnished me with several lower jaws of a fossil Neotoma , 
considerably larger than that of the largest specimen even of any recent species which I have seen. 
The body could not have been less than twelve inches in length ; it differs from the others in 
the wider and more massive molars, the lobes of which are all more nearly equal than in the 
rest, and all rounded, not angular. The inner and outer sides of the molars are very nearly 
symmetrical, and the indentations or folds of nearly equal depth. The axis of the condyloid 
process is quite oblique, and the condyle below the level of the coronoid. The species may he 
called N. magister. 
List of specimens .* 
i All the measurements except those of the feet taken before skinning. 
