228 REPORT OF NATIONAL MUSEUM, 1898. 



The nearctic representatives of 'the IguauidsB agree in possessing the 

 following characters : 



Tongue thick, fleshy, mnch depressed, attached firmly to the integ- 

 ument of the lower jaw, slightly free along the sides and at the tip 

 only (not behind), which is sometimes free for one-fifth, sometimes 

 scarcely at all; end of tongue generally slightly notched (not at all in 

 AnoUs), never bifurcated, and with two oval or triangular smooth disks 

 beneath the tip, varying in size with the extent of freedom, the termi- 

 nal notch being between these anteriorly and deeper as these are larger; 

 tongue behind with a deep, wide notch, embracing the free end of the 

 larynx, which is separated from the tongue proper by a depressed 

 space (entrance in the notch) ; surface of the tongue uniformly and 

 firmly papillose to the end; frenum of tongue single, median, and 

 fleshy. Teeth always more or less compressed and three to five cusped 

 posteriorly. Scales on the body rather small, generally subrhomboidal 

 and arranged in slightly oblique series, more or less imbricated, most 

 distinctly so anteriorly. 



Eyelids present in all. Males distinguished from females by the 

 plates behind anus larger than the rest. Scales on the back arranged 

 on each side of a central dorsal series. 



The superciliary scales are imbricate in front and sometimes behind, 

 except in Sauromalus and Anolis, where they are serial or segmental. 



The genera which enter the nearctic fauna may be compared as fol- 

 lows. They agree in the characters enumerated in the first paragraph. 



Thighs with femoral x>ores; no preanal ones. Orifice of posterior 

 nares much anterior to middle of palate. Digits more or less cylindri- 

 cal; never partially expanded. Under surface of the digits generally 

 in one series of transverse lamellai, but these always have four or more 

 ridges, forming conspicuous longitudinal series and imparting to each 

 plate a strongly anterior serrated edge. Throat without longitudinal 

 fold. A median mental plate. 



A. Throat without any flat fold or collar. Head without spines. 

 Sceloporus. — Upper labials rectangular ; not imbricated. No palatine 



teeth. Head covered with rather large, regular, jilates, in definite 

 series; the supraorbitals distinct. Side of neck with a short oblique 

 fold overlapping a cavity lined with smaller scales. Scales above 

 keeled, usually mucronate; all with more or less lateral denticulation. 

 Sides of belly and usually chin with large blue patch, varied with black 

 in males. 



Lysoptychus. — Upper labials rectangular, not imbricate, and other- 

 wise as Sceloporus. A loose fold of integument crossing gular region, 

 without specialization of scales into a collar. Sides of neck plicate. 



B. Throat with transverse folds, with marginal scales anterior to the 

 breast. Head without spines. Sides of body usually with one lateral 

 fold of skin. Sides of neck variously plicated. External ear wanting 

 only in RolhrooMa. Head covered with small, rounded plates in indefi- 

 nite number, except in Uta. 



