A Synopsis of Recent North American Microtine Rodents by Emmet T. Hooper and Barbara S. Hart compares morphological data from 33 species of microtines—25 from North America and eight from the Old World—through detailed measurements and illustrations of the glans penis. Notable contributors to this data include Tullberg, Bittera, Tokuda, Ognev, Hamilton, Dearden, and Anderson, whose works primarily focused on the Old World's rodent fauna. This study aims to bridge the gap by integrating morphological data with skin and skull features to provide a clearer taxonomic classification of the New World microtines. The research received support from the National Science Foundation and contributions from various collections and individuals who provided specimens. The processing involved formalin preservation, staining, and detailed measurements facilitated with a camera lucida. The accompanying illustrations by Suzanne Runyan exhibit diagnostic features crucial for species identification, improving our understanding of microtine rodents' classification and morphological affinities.