This subspecies of Boat-tailed Grackle has been recorded from several localities in Coahuila. In southeastern Coahuila, Burleigh and Lowery (1942:205-206) noted this grackle "somewhat local in its distribution; it was found in cultivated fields about the towns and villages." These authors noted it at Saltillo, the Chorro del Agua, and "occasionally in the open valley south of Diamante Pass" and obtained specimens from "near Saltillo" and Diamante Valley. On August 18 Amadon and Phillips (1947:579) found _C. m. prosopidicola_ at Las Delicias where "a fledged young was noticed begging for food...." Lowery (1938:4) recorded one specimen of _C. m. prosopidicola_ from Monclova. Findley saw Boat-tailed Grackles 2 mi. W Jimenez on June 19, 1952, and 2 mi. S and 11 mi. E Nava on June 15, 1952. The distribution and intergradation of Boat-tailed Grackles in Coahuila is presently poorly understood. _C. m. prosopidicola_ from southeastern Coahuila may approach _C. m. mexicanus_, and there is probable intergradation of _prosopidicola_ with _monsoni_ in northwestern Coahuila (Phillips, 1950:78). _Molothrus ater ater_ (Boddaert).--_Specimen examined:_ one, [Female] 31513, from 21 mi. S, 11 mi. E Australia, 4400 ft., May 3, 1954, measurements: wing, 102 mm.; tail, 64 mm.; tarsus, 26 mm.; culmen, 17 mm. This subspecies of the Brown-headed Cowbird is uncommon in Coahuila. Amadon and Phillips (1947:579) took an adult male and a juvenile female _M. a. ater_ at Las Delicias on August 15, both of which were considered early migrants. Dickerman obtained No. 31513 from a flock of eight cowbirds. Although the measurements of this specimen agree equally well with those of _M. a. ater_ and _M. a. artemisiae_ (Grinnell, 1909:275-281), the shape of the bill most closely resembles that of _ater_. Grinnell (1909:278) said that "_ater_ has a tumid bill, broad and high at [the] base with [a] conspicuously arched culmen" whereas "_artemisiae_ has a longer and relatively much slenderer bill, vertically shallow at [the] base and laterally compressed, with the culmen in its greater portion straight or even slightly depressed." The size of the ovary (8x4 mm.) of No. 31513 and the date (May 3) on which it was obtained suggest that this individual was a late migrant, still south of the breeding range of _M. a. ater_. _Molothrus ater artemisiae_ Grinnell.--This subspecies of the Brown-headed Cowbird is an uncommon migrant in Coahuila. Amadon and Phillips (1947:579) obtained, at Las Delicias, a juvenile male on August 15 and an adult male on August 17.