Fresh-water molluscs from New Mexico and vicinity

Abstract

Nine new species are described from New Mexico, four from Arizona, two from Utah, and five from Texas, with redescriptions of two more from New Mexico and Texas. These 22 species are classified in Assimineidae (one species of Assiminea), Hydrobiidae (11 species of Fontelicella and two monotypic new genera, Apachecoccus and Yaquicoccus), Littoridinidae (seven species of Tryonia), and Sphaeriidae (one species of Pisidium). Virtually all are narrowly local forms, and have been considered actually or potentially endangered species. Geological significance of these species lies in the drainage history of the region. They conform to previous geological interpretations in showing that they evolved in separate drainages of Pliocene or older times, which have been united into the present stream systems.