Field Colu.mbian Muskum — Zoology, Vol. III. 



die rays the longest, about ^ longer than the head; pectoral i^ in 

 the head; ventral i^. Color light olivaceous, somewhat reticu- 

 lated above ; side with 5 -oblong dark blotches, the last and smallest 

 one forming a black caudal spot; spinous and soft dorsal barred; 

 caudal fin barred; other fins plain; the middle p.ortion of ventrals, 

 except a small central light patch, blackish; some black on pos- 

 terior half of anal fin; a narrow dark curved streak at base of pec- 

 toral fin; a dark stripe on cheek and -one downward and forward 

 from eye. La Antigua. Named for Hon. Powell Clavton, U. S. 

 Minister to Mexico. 



PLEURONECTID.E. 

 Etropus crosotus Jordan & Gilbert. 

 La Antigua, 3 specimens. 



NOTES ON GEOGRAPHICAL DISTRIBUTION. 



Northern Mexico. 



Very little is known concerning the fishes of Sonora and that 

 portion of Chihuahua which lies in the Pacific coast drainage; 

 and while we are not justified in making any generalizations 

 regarding geographical distribution, yet there seem to be a few; 

 facts worth mentioning. 



Sonora and Western Chihuahua is mostly drained by two 

 large rivers, the Rio Sonora and the Rio Yaqui; from these 

 two river basins are known at present 16 species of fresh Avater 

 fishes: 14 from the Rio Yaqui and 4 from the Rio Sonora; 

 two species, Catostotnus bcniardini and Agosia chi-ysogastcr being 

 common to both river basins. From the Gila River in Arizona 

 are known 11 species of fishes; of these, two species, Leuciscus 

 niger and Pixchociicilus Iiictus, have been taken in the Rio 

 Sonora, and Agosia chrvsogaster and Pivcilia occidentalis in the 

 Rio Yaqui, Agosia chrvsogastcr being found in all three river 

 basins. 



There is a considerable area in Northern Chihuahua west of 

 the Rio Grande and adjacent to the head waters of the Gila River, 

 the Rio Yaqui and the Rio Conchos, which is drained by 4 

 small river systems, all of wdiich have no outlets; the Rio Car- 

 men which drains into Lago de Patos, the Rio Santa Maria 

 which drains into Lago de Santa Maria, the Rio Casas Grandes 

 which drains into Lago de Guzman, and the Rio Castillos which 

 drains into Lago de Castillos. These 4 basins have not 



