8 



SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I25 



(principal branch of the Sierra Madre), which rise to heights ap- 

 proaching 14,000 feet (pi. 2, fig. i); (4) the plateau region (Los 

 Altos), which is composed of innumerable ridges and slopes, the 

 majority between 6,000-8,000 feet, a number of rather extensive areas 

 above 10,000 feet, with occasional drops to 5,000 feet, and a few iso- 



51. GULF OF MEYtCO 



DEMie-^ REGIONS 



DISTRIBUTION 



OF 



ONCHOCERCIASIS 



1 N 



WESTERN HEMISPHERE 



Map I. 



lated ridges above 1 1 ,000 feet ; ( 5 ) the Verapas region with its low 

 mountains, luxuriant rain forest, abundant streams, and almost daily 

 rains (only the southern band of Baja Verapaz is extremely dry) ; (6) 

 the semi-arid valley of the Motagiia River, which typifies the arid 

 tropical zone of Guatemala, the northern limit of which extends to 

 the slopes of the Sierra de las Minas (this area usually receives only 

 a few inches of rainfall a year) ; and (7) the moist lowlands of the 

 Atlantic coast, including the Plain of the Peten, which comprises about 



