=Spermophilus variegatus couchii= Baird Rock Squirrel 1855. _Spermophilus couchii_ Baird, Proc. Acad. Nat. Sci. Philadelphia, 1:332, April, type from Santa Catarina, a few miles west of Monterrey, Nuevo León. 1955. _Spermophilus variegatus couchii_, Baker, Univ. Kansas Publ., Mus. Nat. Hist, 9:207, June 15. _Distribution in Tamaulipas._--Possibly in southwestern part; reported only from Ciudad Victoria (Howell, 1938:141). Since Baird (1855:332) described _S. v. couchii_ and mentioned a specimen from Ciudad Victoria that was obtained by Berlandier, no other record from Tamaulipas has come to light. Probably the species obtained by Berlandier was introduced at Ciudad Victoria by man. =Sciurus aureogaster aureogaster= Cuvier Red-bellied Squirrel 1829. [_Sciurus_] _aureogaster_ Cuvier, _in_ Geoffroy St.-Hilaire, and F. Cuvier, Hist. Nat. Mamm., 6, livr. 59 pl. with text, September (binomen published only at end of work, table générale et méthodique, 7:4, 1842), type locality "California"; restricted to Altamira, Tamaulipas, by Nelson (Proc. Washington Acad. Sci., 1:38, May 9, 1899). _Distribution in Tamaulipas._--Tropical forest of southern part; north at least to Rancho Santa Rosa. According to one collector (Schaldach), natives referred to _Sciurus aureogaster_ as "ardilla pinta" or "ardilla colorada." He recorded in his field notes that _S. aureogaster_ was most active between 7:00 and 9:00 a. m. and again from 3:00 to 5:00 p. m., that the nest was constructed of green oak leaves, and that the nest resembles somewhat in size and form that of _S. carolinensis_. Of 53 specimens examined, 17 are black and one from 70 kilometers south of Ciudad Victoria is clearly more whitish than the others. Specimens from the northeastern part of the range of the species (= southeastern Tamaulipas) average darker than those from the south and west. In individuals that are not black, the ventral reddish color covers the shoulders and in some it extends between the shoulders to the median dorsal area. Among females collected from December through May, only one, taken 43 kilometers south of Ciudad Victoria on March 17, was pregnant (one embryo). The weight of seven adult males from Soto la Marina and the Sierra de Tamaulipas averaged 492.5 (400-575) grams. Specimens herein reported from San Fernando provide the northernmost record of the species.