the dune area, especially alon^ its flanks where the sand is just 

 passing by rather than encroaching frontally. the ordinary vege- 

 tation makes valiant efforts to grow onto the slopes, and m many 

 places it has actually almost covered them with greenery. The 

 ubiquitous mest^uite has gained a foothold in small patches 

 hard by the dunes; and nothing can be more exquisite than one 

 of these trees with its dark, twisting trunk and branches and its 

 feathery bright green foliage dancing above the rim of a pure 

 white dune under an azure sky. 



DISAPPEARING MICE AND LIZARDS 



The dunes are not entirely lifeless in other respects, for a few 

 small animals have adapted themselves to these exceptional con- 

 ditions in a most remarkable manner. Notable are a mouse and 

 a lizard. The first is a kind of Pocket Mouse (Peromyscus) of a 

 species that ranges quite widely over the whole region. Where it 

 lives on ordinary soil it is of a normal reddish brown color: but 

 on the adjacent black lava flows it has developed an almost pure 

 black form, and on the white sands all the individuals are as 

 nearly white as a mammal can be without being a full albino. 

 Only over their rumps is there a slight creamy wash, while their 

 large eyes remain black and stand out like jet buttons. They are 

 engaging little creatures that literally whiz over the firm crust 

 of the sand, their legs going so furiously they are invisible. They 

 can also jump prodigiously and can dive into and under the 

 softer sand. 



These mice live in tunnels dug in the compacted sand either 

 just under the surface or deeper down where there is moisture, 

 but the entrances to these tunnels are often at some depth under 

 the soft surface. To get in. the mice just dive in and bore or 

 'swim" their way down to their tunnels. How they know exactly 

 where these hidden entrances are on what must be. to them, 

 veritable continent-wide stretches without any landmarks (for 

 the sands are constantly shifting) is a mystery: but they seem to 

 go below with unerring accuracy. By judicious probing, more- 

 over, you will eventually find your finger entering a firmly con- 

 structed little tunnel. I may say that in doing this once I was 

 greatly surprised to receive a sharp bite from the apparently 

 infuriated occupant. 



The other outstanding animal of the white sands is a small 

 lizard about four inches long of the genus Sceloporus. This is a 

 large genus with a wide distribution, and the species vary enor- 

 mously in color and pattern. Those around the dune area are of 

 sundry grays and browns: those on the dunes are almost pure 

 white with a yellow wash only on the back, but they have in 

 and just behind their armpits, on either side, two jet-black spots. 



Right: This is the region of the most preposterous-looking 

 of all rabbits, the Antelope Jack. It is among the half-dozen 

 fastest living things. 



Overleaf left: The Palo Verde, one of the commonest trees 

 of desert and scrublands, belongs to the pea-and-bean 

 family, has tiny transient leaves, and develops pods Top 

 right: The strange spiny Ocotillo Not a cactus but a shrub 

 related to the candlewoods. it bears small green leaves and 

 puts out flame-colored flowers. 



Bottom right: The well-known Horned Toad (Phrynosoma). 

 actually a flattened, short-tailed lizard of the iguanid fam- 

 ily, is a very common member of the desert fauna. 



nil; \\\C, BEND 



If we travel from these mysterious sands in a s<nitheasterly 

 direction, skirting the south end of the Sacramento Mountains, 

 we will run parallel to the course of the Rio Grande River This 

 is open, intensely dry. and hot country covered with widely 

 scattered cactus and low scrub and is appropriately known as 

 the Salt Basin It narrows rapidly to the southeast and enters a 

 considerable pile of mountains forming a complex jumble be- 

 tween the Rio Grande and the Pecos rivers and terminates in the 

 south in what is called the Big Bend. Here are the remarkable 

 Chisos Mountains. To the north of this strip lie granite escarp- 

 ments with gulley-like valleys filled with small junipers or 

 groves of willows following meandering streams. These gulleys 

 end abruptly on the southern edge of the prairies, which are 

 there (the Tonah Basin) as flat as any in the world. 



The Big Bend is the block of territory contained in a great 

 swing to the south made by the Rio Grande. Happily for geolo- 

 gists, zoologists, and botanists, a substantial area at the southern 

 tip of this territory has been set aside as a national park. At the 

 angle in this bend lie the Chisos Mountains, a compact, more or 

 less circular area with two outliers of different formation, stand- 

 ing on the northern bank of the river At the foot of these on the 



