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



Southern Railway, about 70 miles N.W. of the town of 

 Oaxaca, and situated almost at tlie bottom of the deep 

 depression in which collect the head-waters of the River 

 Papaloapan, which mighty river empties itself into the lagoons 

 near Alvarado, south of Vera Cruz. The bottom of the depression 

 is only 600 metres, about 1900 feet, above sea-level, and a rather 

 steep ascent leads to the plateau of the Valley of Oaxaca, 

 1600 m. = 5250 feet, with an intervening ridge of still greater 

 height. Towards the north-west the ascent out of the gorge is 

 moi-e gradual, but it reaches, before Puebla, an altitude of nearly 

 8000 feet. To the west is a succession of liigh mountains. The 

 climate in this long depiession is very hot, thoroughly ti-opical, 

 but of the dry type, as shown by the prevalence of Organ-cactus, 

 small Mimosas, and scrubl>y Acacins, with scanty low vegetation 

 on the red, gravell}' rubble which forms the subsoil. 



We are still in complete zoological ignoi^ance about the country 

 for at least 120 miles all around Cuicatlan, except the neighbour- 

 hood of the town of Oaxaca. There occui- oidy C. me.vicaiins and 

 G. hocourti; to the east of the depression are dense mountain- 

 forests, in which lower down lives only C. gntfMas with Ameiva; 

 at Puelila lives C. communis occidentalis, which in its striking- 

 pattern, but not structui'ally, bears a great resemblance to the 

 Cuica.tlan specimens. 



Hnqyi^aocidars always 4, followed behind Iiy many small granules, 

 especially when (3 specimens) the posterior supraocular is ex- 

 tremely small, almost reduced to the vanishing point. 



Frenocular present in 11 specimens; two specimens have a 

 frenocular on the right side only ; in the 12th, a yomig specimen, 

 the fi'enocular of both sides is fused witli the first preocular. 



Collar (text-figs. 64 0, 65 F) composed of mostly medium-sized 

 to rather small scales, sometimes passing quite gradu.ally into tlie 

 gulars. In nearly all specimens at least some granules are visible 

 between the scales of the posterior border, and sometimes these 

 granules form a complete row. But in the largest specimen, and 

 in one of 72 mm., the scales forming the edge are distinctly lai-ge. 



Ihmierus covered in front with many rows of scales, about 8 to 

 10 in all; sometimes they decrease in size from befoi-e backwards, 

 and as a rule the hindmost rows are continuous with the slightly 

 enlarged granules of the forearm ; but in most cases some of the 

 front I'ows, either 2, mostly 3, rarely 5 or 6, are distinctly lai-ger 

 than the rest. 



Forearm covered in front with 2^, mostly 3, complete rows of 

 scutes. 



Forearm, posterior surface, never covered with scutes or scales. 

 In 5 specimens the graniiles are almost imperceptibly lai-ger than 

 the rest ; in 5 other specimens are several I'ows of slightly en- 

 larged granules, either near the elbow or near the wrist ; only in 

 2 specimens enlarged polygonal granules form three long rows. 



Femur. — The rows of scales show a continuous vai-iation from 

 6 to 9. 6 occurred 3 times ; 6 to 7 iriegular twice ; 6 right, 



