138 3. IGUANIDM 



for the nearest dune and turn behind it to enter a Dipodomys 

 or Citellus hole or to bury themselves quickly in sand as 

 the gridiron-tails do, the broad nose of which lizards their 

 own shovel-like snout resembles. The tracks of the hind 

 feet of a Uma running at top speed are five to six inches 

 apart j and the deep imprints of these members indicate that 

 most of the work is done by the hind legs, the fore limbs 

 being merely used to balance the creature. The tail is 

 curled upward while running, as in Callisaurus. 



"Their curious color patterns, though they may seem 

 unduly striking when viewed in the specimen in hand, really 

 harmonize in strong light with the buff tint of the sands, 

 and the lizards are seldom detected until they begin to 

 move. 



"One stomach was filled with a great number of ants. 

 Another contained two grasshoppers entire, one large hemip- 

 ter, eight red ants, two brown ants, two beetles, a pebble, 

 and several pieces of vegetation. Another held seven brown 

 and seven red ants, one beetle, several parasitic nematodes, 

 and two fresh leaves and the terminal bud of a plant. One 

 specimen when shot had a plant stem in its mouth." 



Genus 8. Callisaurus 



Callisaurus BLAINVILLE, Nouv. Ann. Mus., Vol. IV, 1835, p. 286 (type, 



draconoides) . 



Megadactylus FITZINGER, Syst. Rept., 184-3, p. 59 (type, draconoides) . 

 Homolosaurus HALLOWELL, Proc. Acad. Nat. Sci. Phila., 1852, p. 179 



(type, ventralis). 



The lizards of this genus have the body and tail con- 

 siderably flattened, legs very long, and the head rounded 

 when seen from above but pointed in profile. The head is 

 covered with irregular plates, the largest of which is the 

 interparietal. The labials are produced laterally and are 

 strongly imbricate. The superciliaries are imbricate. The 

 ear-opening is large, but is without anterior denticulation. 



