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



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

 Oaxaca, and situated almost at the 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 Yera Oruz. 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 Oa,xaca, 

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

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

 more gradual, l)ut it reaches, before Puebla, an altitude of nearly 

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

 climate in this long depression is very hot, thoroughly tropical, 

 but of the dry type, as shown by tlie prevalence of Oj-gan-cactus, 

 small Mimosas, and scrubby Acacias, with scanty low vegetation 

 on the red, gravelly rubble which forms the subsoil. 



We are still in complete zoological ignorance about the country 

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

 hood of the town of Oaxaca. There occur only G. inexicanus and 

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

 forests, in which lower down lives only G. guttattts with Ameiva; 

 at Puebla lives G. comonunis occidentalis, Avhich in its striking 

 pattern, but not structurally, benrs a great resemblance to the 

 Cuicatlan specimens. 



Supraoculars {ihvRjfi 4, followed behind l^y many small granules, 

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

 tremely small, almost reduced to the vanishing point. 



Frenocular present in 11 sj)ecimens ; two specimens have a 

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

 the frenocular of both sides is fused with the first preoculai'. 



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

 to rather small scales, sometimes passing quite gradually into the 

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

 between the scales of the posterior border, and sometimes these 

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

 in one of 72 mm., the scales forming the edge are distinctly large. 



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

 10 in all; sometimes they decrease in size from before 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 rows, either 2, mostly 3, rarely 5 or 6, are distinctly larger 

 than the rest. 



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

 scutes. 



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

 In 5 specimens the granules are almost imperceptibly la,rger than 

 the rest ; in 5 other specimens are several rows 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 variation from 

 6 to 9. 6 occurred 3 times ; 6 to 7 irregular twice ; 6 right. 



