Figure l.--General topography of the Isthmus of Tehuantepec. 



part of the Gulf is less than 200 fathoms 

 deep.'' 



Detailed climatic information is available 

 for the Gulf itself in the form of monthly 

 average charts of surface wind, precipitation, 

 cloudiness, etc. (U.S. Navy, 1955; Meteorolog- 

 ical Office, London, 1956), Some of this in- 

 formation is available together with monthly 



T Sea-bottom topography is shown in Topographic Chart 

 No. 9 prepared by the Bureau of Commercial Fisheries 

 and the University of California, Institute of Marine 

 Resources, issued on December 27, 1960 by the Bureau 

 of Commercial Fisheries. 



average weather data for land stations on the 

 Isthmus (U.S. Navy Hydrographic Office, 1949). 

 The main features have been conveniently 

 summarized in a text (U.S. Navy Hydro- 

 graphic Office, 1951) from which the following 

 are extracts. 



The rainy season extends from May to November and 

 the balance of the year constitutes the dry season . . . 

 at Salina Cruz (the annual fall) is 39 inches .... 



Along the lower Mexican coast the prevailing direction 

 of the trades is northwesterly, tending to parallel the 

 coastline .... 



