BREVIORA Museitaim of Connparative Zoology Cambridge, ]Mass. December 10, 1965 Number 236 VARIATION IN THE NUMBER OF MARGINAL TOOTH POSITIONS IN THREE SPECIES OF IGUANID LIZARDS By Clayton E. Ray U. S. National Museum Although tooth counts (more accurately, the number of tooth positions) are customarily given in the description of fossil lizards, their possible taxonomic value is generally unassessable for want of quantitative data on adequate samples of modern lizards. Further, the possible developmental and adaptive implications of tooth number have been inadequately explored. Edmund (1960, p. 66) notes an apparent lack of correlation between wave length in tooth replacement and number of tooth positions in iguanids, but the condition in juveniles of species with long wave lengths, such as Ctenosaura pectinata with 11 teeth per wave, would be especialh' interesting. Hotton (1955, p. 97) in a study of adaptive relations of dentition to diet in iguanids, including C. similis, states regard-ing tooth number only that there are "slight tendencies toward fewer teeth in the maxillary row ... in smaller individuals." The availabihty of adequate, though not impeccable, samples of cranial material (assembled for other purposes) representing Ctenosaura similis, C. pedinata, and Anolis carolinensis suggested the desirability of characterizing these samples statisticalh^, in order to compare ontogenetic and taxonomic variability in number of tooth positions, and strength of correlation between number of tooth positions and length of tooth row among two closely related taxa and one distantly related taxon.