1) This study reports the chromosome numbers of four species of North American mollusks of the poorly understood land snail family Succineidae, and compares this information with that previously reported for the family. 2) Catinella cf. gabbi has six pairs of chromosomes, Oxyloma retusa 19 pairs, Succinea (Calcisuccinea) campestris 18 pairs, and S. (Novisuccinea) ovalis 21 pairs. 3) These data indicate that cytologically Catinella cf. gabbi is closely related to other species of Catinella, especially to C. vermeta, but that Oxyloma retusa is not as closely related to the Asian and European species of its genus. Succinea (Novisuccinea) ovalis has four more pairs of chromosomes than does its Japanese counterpart, S. (N.) horticola, which indicates that they also are not very closely related. 4) Since no other species of the subgenus Calcisuccinea have been studied cytologically, Succinea campestris cannot be compared with other species of its group.

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