200 DR. H. GADOW ON MEXICAN [June 6, 



interesting that these burrowing, slowly moving worm-like 

 creatures have managed to travel over at least 1500 miles of 

 ground, covered with humus, since the close of the Miocene epoch, 

 i. e. since the separation of the Antilles (cf. p. 237). A not 

 unreasonable computation of one million years carries us back into 

 the Miocene epoch. The rate of sjoreading could in this case 

 have been extremely slow, only about one mile in 700 years, and 

 this works out at three yards a year. Of course this is mere 

 speculation, but it may be as well to give even such an imaginary 

 instance of slow spreading. The fact remains that Dermophis 

 has done it, and whether we double or treble the rate of progress, 

 or increase the time two- or three-fold, the result remains within 

 very reasonable possibility. 



Urodela. 



The Amhlystomatmm are a pre-eminently Eastern Paltearctic 

 group ; only two out of eight genera occur in North America : 

 Dicamptodon eusahos in California, and Anihlystoma, with some 16 

 species, on the North- American Continent, and one, A. jjer simile 

 in Siam. In Mexico only two species occur. 



Amhlystoma tigrinuvi, the larval form of which, when per- 

 manent, is the famous Axolotl. This species has an enormous 

 range, from the State of New York to Dakota and Colorado, whence, 

 apparently noAv with wide gaps between, it extends through 

 Mexico, as far south as the valley of Mexico City. But its dis- 

 tribution in Mexico is, at least now, restricted to the western 

 Sierra Madre and the southern part of the Mexican plateau. 



Well-ascertained localities of this species are the following : — 

 West of Chihuahua Town ; West of the town of Durango ; 

 Cumbre de los Arrastrados in Jalisco ; someAvhere N.W. of Guada- 

 lajara ; district of Autlan in Jalisco ; Lake Patzcuaro in Michoacan, 

 Yalley of Mexico, notably Lakes Xochimilco and Zumpango 

 (but not Lake Texcoco, to which alone Weismann's dismal dream 

 to account for the permanent Axolotl stage could apply !). 

 Possibly there are Amhlystoma, either metamorphosing or as 

 Axolotls, in or near some of the other lakes of Michoacan and 

 Jalisco, but they have as yet not been recorded from Lake Chapala ; 

 and 1 found none in the Lakes of Zapotlan ; nor were such 

 creatures, or even the name Axolotl, known to the natives. 



A . altamircmi. — This species, which metamorphoses regularly into 

 a gill-less Newt, is known only from the streams of the mountains 

 which border the western and south-western side of the Yalley of 

 Mexico. It was discovered in the Montes de las Cruzes, about 15 

 miles to the west of Mexico City, at an altitude of 8800 feet. In 

 1902 I found it also above Contreras, in the Sierra de Ajiisco, 

 some 12 miles south- southwest of the city, at an altitude from 

 8500 feet vipwards to 8800 feet. Further up the rivulets are 

 apparently too small. I stated in ' Nature,' Feb. 5, 1903, that 

 searching in the streams onh- a little above the City of Mexico, 



