172 NORTH AMERICAN FAUNA. [No. 7. 



forming a singular gymnastic exercise, consisting in rapidly dropping 

 and elevating the body with the knees held stiff at right angles to the 



trunk. 



This species feeds on insects and the blossoms and leaves of plants 

 in about equal proportion; at least such was the case in the large num- 

 ber whose stomachs were examined. 



The gridiron-tailed lizard is common throughout the Mohave Desert 

 proper, but does not reach the extreme western end of the desert in 

 Antelope Valley, which, owing to its greater altitude, passes out of the 

 Lower Sonoran zone. It was last seen in this direction about 10 miles 

 east of Liebre ranch. In the wash leading from the Mohave Desert to 

 Tehachapi Valley it was seen up to 1,030 meters (3,400 feet) and may 

 range higher. It is common in the Lower Sonoran zone at the south 

 end of Owens Valley, and ranges up on the warm east side of the val- 

 ley as far as Big Pine. It is common throughout Pan ami nt and Death 

 valleys and in the Amargosa Desert. In Nevada it inhabits the deserts 

 of the southern part of the State, from Ash Meadows easterly across 

 Pahrump and Vegas valleys to the Great Bend of the Colorado, where 

 it is very common, and ranges north through the valleys of the Virgin 

 and Lower Muddy (where it is abundant) to Pahranagat and Meadow 

 Creek valleys. In western Nevada it comes through Grapevine Canon 

 (from the northwest arm of Death Valley), ranges easterly over 

 Sarcobatus Flat, and ascends the warm south slope of Gold Mountain, 

 with Larrea, to about 1,640 meters (5,400 feet). In Utah it is common 

 in the Lower Santa Clara Valley, but does not range up into the sage- 

 brush or Upper Sonoran Zone of the upper part of the valley. 



In Desert Valley, just east of the Pahroc Mountains, a form of this 

 species was found which seems to be subspecifically distinct from the 

 ordinary type. It is much shorter and broader, with a shorter tail, and 

 is bluish-gray in color. It may be the same as the animal inhabiting 

 the desert at Pyramid Lake, Nevada, which point is about two degrees 

 further north than Desert Valley, though in the same zoological sub- 

 zone, for the low altitude of a series of narrow and irregular deserts in 

 western Nevada carries this zone much further north than elsewhere. 

 These specimens suggest the existence of a form peculiar to the upper 

 division (or Grayia belt) of the Lower Sonoran Zone, Callisaurus ven- 

 tralis proper being closely restricted to the lower division (or Larrea 

 belt) of the same zone. — O. H. M.J 



