170 ANIMAL LIFE OF CARLSBAD CAVERN 



and even running over the buildings about the cave 

 shafts. Widely differing groups are represented, as the 

 rough, scaly rock lizards (Fig. 62) ; the smooth, slender 

 whip-tailed lizards (Fig. 63); the big, brilliantly 

 colored collared lizards (Figs. 64 and 65); the bar- 

 tailed Texas lizards; several groups of small, plainly 

 colored and little noticed species; and two, if not three, 

 kinds of horned lizards (Fig. 66), commonly called 

 "horntoads." A close study at favorable seasons of 

 the year would undoubtedly disclose many other species 

 and groups, and possibly some forms that have not 

 been previously recognized. All are harmless and very 

 useful, as well as very interesting, animals, well worth 

 a careful study of habits. Most of their food consists 

 of insects and other small forms of animal life, the 

 destruction of which is not only important to our 

 human interests, but necessary in the balance of nature 

 that tends to prevent the sudden increase of highly 

 destructive species. 



TURTLES 



Turtles of several species inhabit the Pecos and 

 Black rivers, and pieces of their bones and shells 

 uncovered from old camp fire sites in the sand dunes 

 along the river banks show that they had an economic 

 value to the prehistoric tribes of this region. A small 

 box tortoise is occasionally found along the valley at 

 a distance from water, and even in the driest situa- 

 tions. This species seems perfectly adapted to desert 

 life and is able in some way to obtain sufficient mois- 

 ture for its needs. 



