Fusulines collected by Ralph W. Imlay from three measured sections in Sonora indicate a considerable thickness of Permian limestone, probably of Leonard age. One collection shows the presence of Pennsylvanian rocks also.
Eight species of fusulines are illustrated, and three new species are named. These are Parajusulina imlayi, P. skinneri, and P. sonoraensis.
The fusulines indicate that, during Leonard time, Sonora belonged to a faunal province distinct from central Mexico and west Texas.