496 MR. G. A. BOULBNGER ON THE [May 18, 



2. Forma typica. Femoral pores 7-10 ; auricular scales usually 

 not or but slightly longer than broad. 



3. Var. darhii, B. & Gr. Femoral pores 11-13 ; auricular scales 

 not longer than broad. 



4. Var. mac/ister, Hallow. Femoral pores 11-17 ; auricular 

 scales usually much longer than broad. 



Hah. Mexico west o£ the Isthmus of Tehuantepec ; northwards 

 to Nevada, Utah, Colorado, Texas, and "Western Florida. 



11. SCELOPOBTJS ACAIfTHINlJS. 



Sceloporus acantJiinus, Bocourt, Miss. Sc. Mex., Eept. p. 180, 

 pi. xviii. fig. 10, & pi. xix. fig. 4 (1874) ; Cope, Proe. Amer. Philos. 

 Soc. xxii. 1885, p. 396; Bouleng. Cat. Liz. ii. p. 221 (1885); 

 Gunth. Biol. C.-Am., Kept. p. 65 (1890). 



Sceloporus spinosus, part., Giinth. 1. c. p. 63. 



Scelopoms viviparus (non Cope), Giinth. 1. c. p. 64. 



Head- shields smooth ; frontal transversely divided, rarely 

 single, in contact with the interparietal ; latter as long as broad 

 or a little longer than broad, broader than the parietals ; a series 

 of four or five large transverse supraoculars, bordered inwards by 

 a complete or incomplete series of scales, the last two plates 

 rarely in contact with the frontoparietals and parietals ; one or 

 two series of scales between the large supraoculars and the 

 supraciliaries ; two canthal scales ; four or five pointed scales, not 

 or but little larger than those before them, form a denticulation 

 in front of the ear. 



Dorsal scales much larger than ventrals, as long as broad or 

 longer than broad, strongly keeled and mucronate, denticulate, the 

 keels forming parallel or slightly oblique series; 26-32 scales 

 between the interparietal shield and the base of the tail ; 6 or 7 

 scales, taken in the middle of the back, correspond to the length 

 of the shielded part of the head (8 in some young, owing to 

 the proportionally larger head). Lateral scales graduating into 

 dorsals and ventrals, strongly keeled, directed obliquely upwards 

 and backwards. Ventral scales small, smooth, bi- or tricuspid ; 

 35-40 scales round the middle of the body. 



The adpressed hind limb reaches the collar-fold or the ear ; 

 tibia as long as or slightly longer than the shielded part of the 

 head ; the distance between the base of the fifth toe and the 

 extremity of the fourth exceeds the distance between the end of 

 the snout and the posterior border of the ear. 14-16 (exception- 

 ally 13 or 17) femoral pores on each side. 



Caudal scales as large as or a little smaller than dorsals, strongly 

 keeled, mucronate, and denticulate like the dorsals. Males with 

 enlarged postanal scales. 



I have examined a good number of specimens, which show the 

 following variations in the proportions, the lepidosis, and the 

 number of femoral pores : — 



