250 PROCEEDINGS OF THE NATIONAL MUSEUM vol. iie 



Eight (27 percent) of the 30 species of amphibians and reptiles 

 recorded from the Zuni region are, so far as known, restricted to this 

 belt. They are Scaphiopus intermontanus , Scaphiopus bombifrons, 

 Bujo pundatus, Uta stansburiana, Holbrookia maculata, Thamnophis 

 dorsalis, Masticophis jiagellum, and Crotalus atrox. Certain other 

 species, especially Sceloporus graciosus, Eumeces obsoletus, Pituophis 

 melanoleucus, and Crotalus viridis, appear to reach their maximum 

 abundance here. 



For the most part, the Plains Life Belt is characterized by the 

 short-grass or mixed -grass association in which blue grama (Bouteloua 

 gracilis) is dominant or codominant with such other grasses as hairy 

 grama (B. hirsuta) and galleta {Hilar ia jamesi) (pi. lA). Holbrookia 

 maculata usually is found where shrub cover is sparse and composed 

 of rabbitbush {Chrysothamnus nauseosus), snakeweed (Gutierrezia 

 sarothrae), or narrow-leaved yucca (Yucca glauca). Reptile life is 

 more varied in somewhat heavier cover, as in the saltbush-sage 

 association dominated by shadscale saltbush (Atriplex canescens), 

 spiny saltbush (A. conjertijolia) , or big sagebrush {Artemisia triden- 

 tata). Sceloporus graciosus is Umited primarily to this vegetational 

 type. Crotalus atrox seems similarly limited to the cholla-juniper 

 association dominated by cholla cactus (Opuntia imbricata) and 

 one-seed juniper {Juniperus monosperma) . 



Between elevations of 6500 and 7200 feet there may be an ecotone or 

 a broad continuum between Plains and Roughlands Life Belts marked 

 by an increased number of one-seed junipers and various taller shrubs 

 such as mountain mahogany (Cercocarpus montanus). Pinyons 

 (Pinus edulus) may be present. The widespread continuum could, 

 in part, be caused by excessive gi'azing (Castetter, 1956, p. 272). 

 Eumeces obsoletus occure here as do most other Plains species that 

 range into the Roughlands. Rock-strewn arroyos also permit species 

 like Crotaphytus collaris and Masticophis taeniatus to bridge the 

 ecological gap between the two life belts. 



Roughlands Life Belt 



The Roughlands Life Belt comprises rocky uplands from around 

 6800 feet to at least 8000 feet. Its outside elevational limits are 

 influenced by the presence of rocky soil combined with the effects of 

 less moisture at lower elevations and lower temperatures in Montane 

 environments (see Castetter, 1956, p. 271). Vegetative cover is much 

 thicker than on the plains, and outcropping sedimentary strata produce 

 boulder piles and talus slopes, thus providing additional retreats for 

 secretive species. This life belt includes the upper part of Bailey's 

 (1913, pp. 25-46) Upper Sonoran Zone and lower limits of his Tran- 



