The book "Geographic Variation of the North American Carpfish, Hybopsis gracilis" gives the reader the opportunity to study in detail the variation within populations of the fish -gyphopsis gracilis in North America. The publication is based on the results of research by the authors - Frank B. Cross and Leonard J. Olund. The book includes important information about the ecology, morphology and genetic structure of this species group. Readers will be able to deepen their knowledge of the geographic distribution and adaptation of Hybopsis gracilis with the information presented in this research book.