83 

 size and structure is discussed. 



226. Uzzell, T. 1970. Meiotic mechanisms of naturally occurring 

 unisexual vertebrates. AMERICAN NATURALIST 10^(939): ^33-^45. 



Six proposed pathways of oogenesis for unisexual vertebrates are 

 reviewed. All parthenogenetic Cnemidophorus probably (although only 

 demonstrated for _C. uniparens ) form ova by suppressing cytokinesis at 

 the last premeiotic mitosis, which is then followed by two meiotic di- 

 visions based on pseudobivalents rather than synapsed homologues. Al- 

 though they are fixed heterozygotes (and thus possibly well buffered 

 against environmental shifts), there is no evidence for great antiquity 

 of any of the unisexual species. The addition of new genetic variation 

 by mutation and the elimination of ill-adapted genomes by selection 

 cannot result in sufficiently rapid evolution to enable them to survive 

 as long as sexual species. 



227. Vance, T. 1978. A field key to the whiptail lizards (genus 

 Cnemidophorus ). Part 1: The whiptails of the United States. BULLETIN 

 OF THE MARYLAND HERPETOLOGICAL SOCIETY iMl): 1-9. 



The key will only identify specimens that are adults, alive or 

 freshly killed, and for which collection sites are known. Tentative 

 range maps are included which are stated to provide a reasonably accu- 

 rate estimate for each taxon. Cnemidophorus dixoni is not recognized 

 to occur in New Mexico; that population is retained as _C. tesselatus . 



228. Van Devender, T. and 3. I. Mead. 1978. Early Holocene and late 

 Pleistocene amphibians and reptiles in Sonoran Desert packrat middens. 

 COPEIA 1978(3): ^6if-^75. 



Cnemidophorus cf . tigris and Cnemidophorus sp. (probably sonorae ) 

 were found. A biogeographical discussion is presented in which the re- 

 striction of desert faunas to Mexican refugia during glacial periods is 

 not supported. 



229. — . and R. D. Worthington. 1977. The herpetofauna of Howell's 

 Ridge cave and the paleoecology of the northwestern Chihuahuan Desert, 

 m TRANSACTIONS OF THE SYMPOSIUM ON THE BIOLOGICAL RESOUR- 

 CES OF THE CHIHUAHUAN DESERT REGION, UNITEDSTATES AND MEX- 

 ICO. Wauer, R. H. and D. H. Riskind, editors. National Park Service 

 Transactions and Proceedings Series No. 3: 85-106. 



The fauna includes Cnemidophorus cf . tigris and C^. spp., and ex- 



