Specimens examined.—A total of 124 (all from Mus. Nat. Hist., Univ. Kansas) from: COAHUILA: 6 mi. E Hermanas, 1; 9 mi. E Hermanas, 1; Panuco, 3000 ft., 4; 1 mi. S, 4 mi. W Bella Unión, 7000 ft., 3; 3 mi. S, 3 mi. E Bella Unión, 6750 ft., 1; 6 mi. E, 4 mi. S Saltillo, 7500 ft., 5; 7 mi. S, 4 mi. E Bella Unión, 7200 ft., 3; 14 mi. W, 1 mi. N San Antonio de las Alazanas, 6500 ft., 2; 12 mi. S, 2 mi. E Arteaga, 7500 ft., 5; north slope Sierra Guadalupe, 10 mi. S, 5 mi. W General Cepeda, 6500 ft., 26; 7 mi. S, 1 mi. E Gómez Farías, 6500 ft., 3; 8 mi. N La Ventura, 5500 ft., 1. NUEVO LEON: Iturbide, Sierra Madre Oriental, 5000 ft., 10; Laguna, 1; 9 mi. S Aramberri, 3900 ft., 3; 1 mi. W Doctor Arroyo, 5800 ft., 4. TAMAULIPAS: Miquihuana, 6400 ft., 22; Joya Verde, 35 km. SW Cd. Victoria (on Jaumave Road), 3800 ft., 2; Nicolás, 56 km. NW Tula, 5500 ft., 10; Tajada, 23 mi. NW Tula, 5200 ft., 2; 9 mi. SW Tula, 3900 ft., 15.
Comparative material.—N. a. albigula, 10 specimens (all KU) from: ARIZONA: 4 mi. S, 5 mi. E Continental, 4; 7 mi. E Tucson, 2500 ft., 1; 30 mi. S Tucson, 1; 14 mi. S, 3 mi. E Continental, 1; Sta. Catalina Mts., south slope Molino basin, 4200 ft., 2; Santa Rita Mts., northwest slope, near Sta. Rita Range, 4300 ft., 1.
N. a. leucodon, 46 specimens (in Mus. Nat. Hist., Univ. Kansas, unless otherwise noted) from: SAN LUIS POTOSI: 6 km. S Matehuala, 13 (LSU); 1 km. S Matehuala, 2 (LSU); 7 km. W Presa de Guadalupe, 5 (LSU); Presa de Guadalupe, 4 (LSU); 8 mi. SW Ramos, 6700 ft., 3; 10 mi. NE San Luis Potosí, 6000 ft., 2; San Luis Potosí, 9 (USNM); Hda. La Parada, 8 (USNM).
I am grateful to Prof. E. Raymond Hall and Mr. J. Knox Jones, Jr., for permission to examine critical specimens and for helpful suggestions. I am grateful also to Dr. George H. Lowery, Jr., of the Louisiana State University (LSU) and to Dr. David H. Johnson and Dr. Richard H. Manville of the United States National Museum (USNM) for the loan of specimens. Gerd H. Heinrich (in 1953) and Percy L. Clifton (in 1961) collected for the Museum of Natural History the Tamaulipan specimens herein reported. Fieldwork was supported by the Kansas University Endowment Association. Laboratory phases of the study were made when the author was a half-time Research Assistant supported by grant No. 56 G 103 from the National Science Foundation.
Transmitted February 21, 1962.
29-2891