352 DR. n. aADOw on evolution [Mar. 20, 



which are t}'pically at home in Mexico extend far into Central 

 America, occasionally cropping np very locally — a sporaflic dis- 

 tribution most likely due to our want of data. 



Two specimens (Brit. Mus.)from the Island of Cozumel, east coast 

 of Yucatan, have to be referred to C. communis copei until more 

 Cnemidophori * from the huge peninsula of Yucatan have been 

 collected. 



There are 4 supraoculars. The collar-scales form complete rows, 

 bvit are distinctly small, as in the Cuicatlan specimens, with which 

 those of Oozumel agree also in the number of femoral rows and 

 pores. The large polygones on the forearm agree with those of 

 San Domingo and Colima. There are 7 pale stripes on the back, 

 all narrow and still complete, but each stripe contains small white 

 specks, and similar small specks ai'e numerous in the fields, on the 

 rump and on the thighs. 



It is noteworthy that several of the upper labials are denti- 

 culated, exactly as in the 0. deppei specimens from the same 

 island ! 



Cnemidophorus communis australis. (Text-figs. 62 C, D ; 

 64C,D; 65 F; 79B,C.) 



Diagnosis : like C. copei, but with entirely granular foi'earm. 



Seven specimens collected by Dr. Meek at Lagunas, a station a 

 little further east than San Domingo, still on the western slope 

 of the Isthmus. — They agree with the typical C. c. copei in the 

 large number of femoral pores, of femoral and humeial I'ows, 

 composition of the large-scaled collar, the large average size of 

 the adults, and by the colour-pattern ; but they differ without 

 exception by the complete absence of any scutes or enlarged 

 polygones on the posterior side of the forearm. It is to be 

 remembered that this character is not veiy reliable in Southern 

 Mexico ; see certain specimens of C. mexicanus from Cuautla, 

 Sojutla, and Oaxaca, and of C. communis occidentalis from Puebla. 

 In some of the 7 specimens the 4th supraocular is very small. 



The evolution of the colour- pattern seems to proceed as follows : — 



In the youngest specimens the first and second paii-s of stripes 

 are still white and complete, quite conspicuous ; the third stripe is 

 becoming faint and breaks up into white spots on the lower back 

 and rump. Fields I. and II. are still black, without any spots. 

 Thighs above still without specks; behind reddish, with spots or 

 traces of a pale stripe. 



In specimen 98 mm., stripes 3 and 2 are fading or becoming 

 grey from the neck backwards, neck and shoulders becoming grey. 

 Small whitish spots appear in one or two rows in fields I. and II. 



* C. aiigusticeps Cope, Proc. Am. Phil. Soc. xvii. 1877, p. 95. Thefom* specimens 

 seem to be the only Cnemidophori known from " Yucatan." 



According to Cope they are like his C communis, but distinguished by the very 

 narrow parietal and interparietal plates. Four supraoculars. Edge of collar 

 composed of large scales. Frenocular present. 



Ground-colour black, and fields much wider and not broken up. The stripes send 

 off lateral processes which give the dark ground-colour a very broken character. 

 Fields green. Adult male of the size of C. conuimnis and C. (/uttatus. 



