TEIID LIZARDS OF THE GENUS CNEMIDOPHORUS 13 



the t()ii<iue than many other specimens of the same species! Thus, 

 even at this date, this criterion was found to be too weak a distinc- 

 tion for a specialist to use with profit and accuracy. 



A strong, prominent, posterior lingual sheath is present in A?)ieiva 

 ameiva ainehca. and certain of its near relatives. This anatomical 

 detail, as found in this particuUvr section, represents an extreme of 

 divergence from Cn&inidophorus^ in wliich the sheath is normally 

 absent, and has been mentioned by some workers as a generic distinc- 

 tion. The sheath may sometimes cover the posterior portion of 

 the scaly part of the tongue and this has given rise to the expression 

 " retractile into a basal sheath " as applied to the tongue of Ameiva 

 by Boulenger (1885). Here again Ameiva offers a close approach 

 to Cnemldophonis, since the sheath is noticeably reduced or weak 

 in certain specimens that have been examined, particularly in Mexi- 

 can Ameiva umliiJata and Ameiva ameiva 'praesi<j)iis^ the most 

 northern mainland representatives of their genus. In this connection 

 it is noteworthy that the sheath is weakly developed in mu/'inus, the 

 type species of Cne/nidophonis, and even in other forms of the genus 

 (such as Mexican gularis) as well. Thus, the sheath is not necessarily 

 a fundamental character, but one subjected to development and loss, 

 as are numerous other pecularities of form that are found in nature. 



Tlie amplitude of variation in coloration and in scutellation is 

 great in both Ameiva. and Cnemielophovus and here it seems apparent 

 that the general generic distinctions based upon them are unreliable. 

 Moreover, every attempt to establish a new grouping of the species 

 fails. The writer considers the number of longitudinal rows of 

 ventral plates of considerable phylogenetic significance, and would 

 propose a separation between the species with eight rows and those 

 w^ith ten if it were not for certain forms, such as Ameiva taenlura, 

 Aineiva. lineolata^ Ameiva maynarell^ and Cnemidoplioi'us murlnus 

 amheiisls^ which may approach either eight or ten rows, the number 

 depending upon an increase or decrease in the size of the lateral 

 granules which in these forms are almost always present along the 

 outer rows of large, full-sized, ventral plates. 



At this point it would seem necessary to synonymize Cnemldo- 

 pliorus with Avieiva, and it must be admitted that there is con- 

 siderable argument in favor of this. Yet, in numerous specimens 

 examined, onl}' tAvo have been found that could not, with due allow- 

 ances, be correctly placed by the differential diagnosis presented in 

 the "Key to CnemldopJionis and Allied Genera," Avhich is given 

 below. These two exceptions {undtdata and praeslgnls, respectively) 

 were both collected in jMexico where the maximum development of 

 Cnemidoplioi-ns occurs and at the extreme edge of the range of 

 Ameiva. Moreover, southern specimens of undtdata and j^/'ae.'i ignis 

 are readily identifiable. 



