The genus Eucyllus Horn is reviewed with the three species: vagans Horn. unicolor Van Dyke, and echinus Van Dyke, redescribed and discussed. Three additional species are described as new: saesariatus from Sonora, Mexico, and Arizona, carinarostris from California, and cinereus from California. Eucyllus tinkhami Tanner is placed in the genus Eucilinns Buchanan. Distributional and biological information is given for each.