184 THE AMERICAN MIDLAND NATURALIST. 
gathered from the Eastern, Central, and Southwestern sections of the 
United States shows constant differences between these forms. 
(5.) The structure of the gonopod of the Eastern form is strikingly 
different in certain respects from that of the two other forms. This 
form deserves specific rank as Gambusia holbrooki Grd. 
(6.) The evidence is, however, not clear for the Central and South- 
western forms that the differences indicate more than varietal relation- 
ships of these forms. The material may be tentatively grouped together 
as Gambusia affinis B. & G. 
(7.) The Mexican species Gambusia senilis has invaded Southern 
Texas, and is now found at San Marcos and other localities. 
LITERATURE CITED. 
EIGENMANN, C. H. (1907.) The Poeciliid fishes of Rio Grande do Sul 
and La Plata basin. Proc. U. S. Nat. Mus. 32: 425-483. 
(1912.) The freshwater fishes of British Guiana, including a study of 
the ecological grouping of species and the relation of the fauna of the 
plateau to that of the lowlands. Mem. Carneg, Mus. 5: 1-578, 103 plates. 
HENN, A. W. (1916.) On various South American poeciliid fishes. 
Ann. Carneg. Mus. 10: 93-142. 
HILDEBRAND, S. F. (1917.) Notes on the life-history of the minnows 
Gambusia affinis and Cyprinodon variegatus. Rept. U. S. Commr. 
Fisheries for 1917. Appendix VI. (15 pp.) 
Kuntz, A. (1914.) Notes on the habits, morphology of the reproductive 
organs, and embryology of the viviparous fish Gambusia affinis. Bull. 
U. S. Bur. Fisheries 33: 177-190. i 
LANGER, W. Fr. (1913.) Beitrage zur Morphologie der viviparen 
Cyprinodontiden. Morph. Jahrb. 47: 193-307. 
Meek, S. E. & S. F. HILDEBRAND (1916.) The fishes of the Canal 
Zone of Panama. Publ. Field Columb. Mus. (Zool. Ser.) 10: 217-374. 
REGAN, C. T. (1913.) A revision of the cyprinodont fishes of the sub- 
family Poeciliine. Proc. Zool Soc. London 1913: 977-1018. 
