3IO PATAGONIAN EXPEDITIONS: ZOOLOGY. 



Gunther has shown that the short and separated water courses are for the 

 most part inhabited by local adaptations or species peculiar to each water 

 system, or two or three of the neighboring systems. For instance, all but 

 two or three of the inhabitants of Lake Peten are peculiar to this small lake. 



For this reason he has been able to divide this province into the follow- 

 ing subprovinces : 



A. Fresh waters north of the Lakes of Managua and Nicaragua, empty- 

 ing into the Pacific. From this subdivision he recorded 22 species, nearly 

 all of them confined to this region. Only 4 of these species extend north 

 as far as the Isthmus of Tehuantepec. Eight are South American, one, 

 Lepisosteiis, is northern, nine are transitional or middle American and the 

 rest are Marine. 



B. The fresh waters north of the Lakes of Managua and Nicaragua, 

 emptying into the Atlantic. From this subregion he recorded 28 species 

 nearly all of which are peculiar. Eighteen are South American in their 

 relationships. Only four species, Pinielodus sahini, Belonesox belizanus, 

 XipJiopliorus he/Icri and Aniemnis ineridionalis (from the LIsumacinta) are 

 found north of the province ; only the last is a northern intrusive. The 

 Rio Motagua contains no North American elements. This subprovince 

 also contains Gymnotits caraJ)o and Symbraiichus nianiiorafiis, the South 

 American species having the farthest range northward. 



C. Lake Peten with 14 species, of which all but two were supposed to 

 be peculiar. 



D. Lake Managua with 6 species. 



E. Lake Nicaragua with 9 species. 



F. The fresh waters south of the Lakes of Managua and Nicaragua to 

 the Isthmus of Darien. (The region about Panama is unmistakably South 

 American, as distinct from Central American.) 



2. Pacific Province. 



The Pacific province includes all the fresh waters emptying into the 

 Pacific from Panama to the southern boundary of Peru, except the head- 

 waters above an elevation of about 3000 feet. It is a narrow strip, nowhere 

 exceeding 200 kilometers in width, and in places less than 50 kilo- 

 meters wide. North of 5° of south latitude it is abundantly supplied with 

 rivers. South of this point the rivers become smaller and of less impor- 

 tance. The rivers are the Mamoni and Chepo in Panama, Rio San Juan 



