The distinctness of M. f. olivacea from M. f. peninsulae is not satisfactorily established due to inadequate material of peninsulae. Differences shown by the specimens seen indicate that, as compared with olivacea, peninsulae is larger, has transversely wider light-colored underparts which possess more yellow, and a larger skull with more inflated tympanic bullae. In each of these characters, olivacea is intermediate between noveboracensis on the north and peninsulae on the south. The question arises, therefore, whether the animals here recognized under the name olivacea really constitute a recognizable subspecies or instead are only representatives of a subspecies which reaches its extreme development in Florida. In the latter event, the name peninsulae would apply to all. Examination of more material from Florida, especially from the southern half of Florida, will be necessary to answer this question.
This large weasel of the southeastern United States is remarkably different from noveboracensis. Indeed, were it not for actual intergrades such as the two from Fort Payne, Alabama, and York, South Carolina, which are described in the account of M. f. noveboracensis, and the six specimens from northwestern Alabama, which are referred to olivacea, the systematist, I believe, would have little or no hesitancy in designating the two as distinct species, especially on the basis of differences to be seen in the skull.
Not only are the two forms structurally more different than usually is the case but between two geographically, adjacent subspecies of the same species of mammal, but the belt where intergradation occurs appears to be narrow. Nevertheless, when material of the two races is laid out in geographic order, and examined in mass, certain features are seen to undergo gradual change as a person's eye travels from specimens from, say, the center of the range of noveboracensis to specimens from southern localities adjoining the territory occupied by olivacea. One of these features subject to gradual change is the color of the underparts. Beginning at the Adirondacks of New York where a large number of the specimens have white underparts, the underparts become more intensely yellowish southward through the range of noveboracensis into that of olivacea. Indeed, this progressive trend seems to continue right on southward through the range of olivacea into that of peninsulae. Turning in the opposite direction we find that the least width of the underparts decreases gradually northward toward the range of noveboracensis. There is, likewise, a decrease to the northward in length of the skull and relative, as well as actual, narrowing of the braincase and tympanic bullae. However, in least width of color of underparts and the mentioned cranial features, the trend stops relatively abruptly at the southern boundary of the geographic range of noveboracensis and does not continue on, northward, into the range of noveboracensis as is the case with the change in intensity of yellowness of the underparts.
Two males, in the United States National Museum, Biological Surveys Collection, from near Leighton, Alabama, no. 178386 from the Tennessee River nine miles north [of Leighton?] and no. 180240 from La Grange Mountain, although clearly referable to olivacea on the basis of cranial characters, show some approach to noveboracensis in lesser size of the skull and agree with noveboracensis in the narrowness of the color of the underparts. Also, these specimens, like others from the northern part of the range of olivacea, for instance, no 31.227, Charleston Museum, from Mayesville, South Carolina, have the color of the underparts extended only part way out on the hind limb toward the foot. In specimens of olivacea from the southern part of its range the color of the underparts is extended onto the hind feet and this trend reaches its extreme in peninsulae, specimens of which have the feet and larger parts of the limbs marked with the light color of the underparts.
An adult female, no. 32.32, Charleston Museum, although typical of olivacea in most respects, is nevertheless an intergrade. The teeth are as small as in some specimens of noveboracensis. The size of the skull is only slightly nearer that of olivacea than it is to that of noveboracensis. The proportions of the skull, however, are distinctly those of olivacea.
Five other specimens, from northwestern Alabama, namely two from eight miles north of Nauvoo, two from Shoal Creek, and one from White Creek, also show intergradation between noveboracensis and olivacea. The remarks concerning color and color pattern of the specimens from Leighton apply equally well to the five from northwestern Alabama. In cranial characters, no. 51658 from Shoal Creek is referable to olivacea, as also is no. 51677 from the same place, providing it is a female rather than a male as sexed by the collector. No. 57146 from White Creek also is referable to olivacea although the skull shows some approach to that of noveboracensis. Of the two males from near Nauvoo, no. 51652 is to me indistinguishable from noveboracensis, but no. 51653 does have some characters of olivacea, although on the whole, the latter, too, seems to be a little nearer noveboracensis than olivacea. However, because the mean of these seven specimens from northwestern Alabama is nearer olivacea than noveboracensis the former name may be applied.
Another specimen from "Souinlonie" Creek, Clark County, Mississippi, has the coloration and rostral configuration of primulina, narrow mastoidal breadth and smaller teeth of noveboracensis and skull of large size with "full" braincase as in olivacea. No. 235364, U. S. Nat. Mus., from the Mobile River at the "L. and N. RR. Crossing," Mobile County, Alabama, although definitely olivacea, shows approach to arthuri in that the dorsal outline of the skull is longitudinally more convex and the tympanic bullae are less inflated than in olivacea and in that the color of the underparts is almost exactly as in the type specimen of arthuri. The young specimen labeled as from "Silver Springs," Florida, has large tympanic bullae (17 mm. long) and several characters that show its relationship to peninsulae as that race is now understood. Because the sex is unknown the identification as olivacea is tentative and is made on the assumption that the specimen is a male. If it is instead a female, the animal is referable to peninsulae.
An adult, female specimen in the Charleston Museum, no. 27.239.1, taken at St. Matthews, South Carolina, on December 8, 1927, contained four embryos which averaged 19 mm. in length and 47.75 centigrams in weight. Another adult female, in the Charleston Museum, no. 32.32, taken on February 21, 1932, at the same place, has prominent mammae, and the collector has noted that two were slightly active.