352 DR. H. GADOW ON EVOLUTION [Mar. 20, 



which are typically at home in Mexico extend far into Central 

 America, occasionally cropping up veiy locally — a sporadic dis- 

 tribution most likely due to our want of data. 



Tivo specimens {Brit. Mus.)froin the Island of Cozitmel, 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, 

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

 those of Cozumel agree also in the number of femoi-al rows and 

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

 San Domingo and Oolima. There are 7 pale stiipes on the back, 

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

 specks, and similar small specks are 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 C. depp)ei specimens from the same 

 island ! 



0."^EMIDOPHORUS COMMUNIS AusTRALis. (Text-figs. 62 C, D ; 

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



Diagnosis : like C. copei, but with entirely granular forearm. 



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 humeral rows, 

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

 the adults, and by the colour-pattern ; but they diifer 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 very 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 pairs 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. angusticeps Cope, Proc. Am. Pliil. Soc. xvii. 1877, p. 95. The four specimens 

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



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

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

 composed of large scales. Prenocular 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. communis and C. gitttatus. 



