Holochilus chacarius Thomas, 1906 . Ann. Mag. Nat. Hist., ser. 7, 18:446.

TYPE LOCALITY: Paraguay, eastern Chaco, one league NW Concepcion, 500 ft .

DISTRIBUTION: Paraguay and NE Argentina.

SYNONYMS: balnearum.

COMMENTS: Considered distinct by Massoia (1980a), who treated balnearum as a synonym; Reig (1986) mentioned balnearum as another good species. Highly variable in diploid and fundamental numbers (Vidal et al., 1976; Nachman and Myers, 1989).