The series of thirty-four specimens from Brownsville, Texas, permits measuring the amount of individual and age variation in several features. For instance, the material is sufficient to show that external measurements of subadults and those that fall in the upper part of the category designated as "young" may be included with the measurements of adults, because the mentioned measurements are not appreciably greater in adults. The series of skulls, although not providing more than six of any one age, shows the range of variation in size and proportion of certain parts and enables the student the better to evaluate cranial characters of nearby races known from only a few specimens. For example, not one of the twenty skulls of males from Brownsville and immediate vicinity is as large as either of the two specimens of texensis from Kerr County.
The white facial markings vary much in size and shape. In the series of thirty-four skins from Brownsville the broad white bands in front of the ears are confluent with the white patch between the eyes on both sides in three specimens and on one side only in six other specimens. These bands are confluent with the color of the underparts in all but two specimens. In one specimen the connection is lacking on both sides and in the other on one side only. A white patch between the ears is present in two specimens. The dark spot at each angle of the mouth is absent on both sides in eleven specimens and absent on one side only in ten others.
In six other specimens from parts of Texas north of Brownsville, the broad white bands in front of the ears are confluent with the white patch between the eyes on both sides in one specimen. A white spot between the ears is present in one specimen. The dark spot at each angle of the mouth is absent on both sides in six specimens and on one side only in three other specimens.
In eleven specimens from México, the broad white bands in front of the ears are confluent with the white spot between the eyes on both sides in two specimens and on one side only in one other specimen. The white spot between the ears is present in one specimen. The dark spot at each angle of the mouth is absent on both sides, in six specimens, and on one side only in one other specimen.
Thus, in 51 specimens the broad bands (one in front of each ear) are confluent with the white patch between the eyes in nineteen out of 100 instances, and not with the color of the underparts in three instances. A white spot between the ears is present in four specimens. The dark spot at each angle of the mouth is present 47 out of a possible 98 times.
Four juvenal specimens from Brownsville, Texas, with their dates of capture and probable age, are as follows: no. 58574, ♀, three weeks old, taken on February 15; no. 17318/24239, ♂, four weeks old, taken on March 16; no. 45899, ♀, forty days old, taken on May 21; no. 21778/36481, ♂, thirty days old, taken on October 20. In the order given, the dates of birth of these four juveniles would be approximately as follows: January 25, February 15, April 1, and September 20. The dates of birth of other specimens less than three months old as judged by the stage of development of the skull, and reckoning backward from the dates of capture, are as follows: April 1, April 30, May 25, October 12, and December 21. Thus, young appear to be brought forth at Brownsville, Texas, in the fall, winter and spring, that is to say from the latter part of September until the latter part of May.
Mustela frenata frenata is either free of the parasites that infest the frontal sinuses of most weasels, or withstands their presence remarkably well, for only one skull shows a definite pathological condition of the frontal sinuses.
Allen (1896:74) quotes H. P. Attwater, with respect to this species in Bexar County, Texas, as follows: "Not common, but occasionally met within the chaparral and cactus lands, where Wood Rats, Rabbits and Quail abound. They were frequently met with around San Antonio during the great 'Tramp Rat' [= Sigmodon hispidus texianus, see Bailey (1905:116)] invasion of 1889-90."
Specimens examined.—Total number, 63, arranged by counties, and in México by states, from north to south. Unless otherwise indicated specimens are in the collection of the United States National Museum.
Texas. Bexar County: San Antonio, 2 (1[2]). Goliad County: Charco, 1. Nueces County: Corpus Christi, 1[2]. San Diego County (not found), 1. Hidalgo County: La Hacienda, 1. Duval County: San Diego, 2[7]. County in question: Lower Rio Grande, 1. Cameron County: Brownsville, 34 (3[2], 4[1], 3[93], 2[75], 1[59], 1[60], 1[4]); no locality more definite than county, 2.
Nuevo León. Río Ramis, 20 mi. NW Montemorelos, 1[90].
Tamaulipas. Matamoros, 6; Miquihuana (now in Nuevo León), 1[75].
San Luis Potosí. Alvarez, 1[75].
México: Region montagneuse des environs de Toluca, Nevada Toluca, 3200 M., 1[84]
Distrito Federal. City of México, 2 (1[4]); Tlalpam, 2. No locality more definite than México, 4 (1[4], 3[7]).