1908.] NATURAL SCIENCES OF PHILADELPHIA. 491 



It slioiikl be added that the existence of zone I, with a mean annual tempera- 

 ture of more than 30° C, rests solely on the authority of the map of Senties 

 and Reyes, that it is doubted by Seiior Pastrana, and that I have not succeeded 

 in finding any records of temperature observations in the valley of the Rio de 

 las Balsas for a period of more than two months. 



For Central America, the temperature records quoted in the paper in the 

 Monthly Weather Review, above mentioned, indicate that in Guatemala and Costa 

 Rica the annual isotherms of 25°, 20°, 1.5°, 10° and 5° C. are situated approxi- 

 mately at elevations of 270, 1,160, 2,050, 2,9.50 and 3,840 metres respectively. 

 The present map, so far as Central America is concerned, has been made from 

 the topographical maps of Dr. Sapper (Petermann's Mittheilungen, L, 1904, and 

 Erqanzungshander XXVII and XXXII, 1S99 and 1905; and Mittelamerikan- 

 ische Reisen und Studien, Braunschweig, 1902) and of the Bureau of American 

 Republics for Guatemala (1902), Nicaragua (1903) and Costa Rica (1903), by 

 using these equivalents. 



