Part 36

=Idaho.= Bannock County: West Fork of Rapid Creek, 9-1/2 mi. E Pocatello, 1.

=Montana.= Meagher County: Camas Creek, Big Belt Mts., 4 mi. S Ft. Logan, 1. Beaverhead County: Donovan, 1. County in question: Yellowstone Park, 1.

=Nevada.= Humboldt County: Alder Creek, 6000 ft., Pine Forest Mts., 1. Ormsby County: 1/2 mi. S Marlette Lake, 8150 ft., 1. Nye County: South Twin River, Toyabe Mts., 1. White Pine County: Baker Creek (8500 ft., 8675 ft., 11100 ft.), 3.

=New Mexico.= Taos County: Twining, 10700 ft., 1. Sandoval County: 9 mi. E Cuba, 9000 ft., 1. Santa Fe County: Saddle S of Santa Fe Baldy, 11000 ft., Santa Fe Range, 1.

=Oregon.= Wasco County: Mill Creek, 20 mi. W Warmsprings, 1. Klamath County: Fort Klamath, 1.

=South Dakota.= Pennington County: 4 mi. SE Hill City, 5300 ft, 2; Pfander's Ranch, 3 mi. SSE Hill City, 5300 ft., 1; Palmer Gulch, 3 mi. SE Hill City, 5300 ft., 1; Spring Creek, 2 mi. W Oreville, 5500 ft., 1. Custer County: 1/2 mi. E Sylvan Lake, 6250 ft., 1.

=Washington.= Columbia County: Butte Creek, 1; Stayawhile Spring, 5150 ft., 1:

=Wyoming.= Crook County: 5 mi. NW Sundance, 5900 ft., 1. Teton County: Whetstone Creek, 2; 1/4 mi. E Moran, 6700 ft., 1. Sublette County: 1/2 mi. NE Pinedale, 7500 ft., 1. Albany County: 30 mi. N and 10 mi. E Laramie, 6560 ft, 1; 26 mi. N and 4-1/2 mi. E Laramie, 6960 ft., 1. Carbon County: 8 mi. N and 19-1/2 mi. E Savery, 8800 ft., 2.

=Mustela erminea? angustidens= (Brown)

Plates 7, 12, 13 and 14

Putorius cicognanii angustidens Brown, Mem. Amer. Mus. Nat. Hist., 9 (pt 4):181, pl. 17, 1908:

Mustela cicognanii angustidens, Hay, Iowa Geol. Surv. Bull., 23:32, 1914; Hay, Carnegie Inst. Washington, Pub. no. 322A:252, October 15, 1924; Hay, ibid., Pub. no. 390 (vol. 2): 528, 1930; Hall, ibid., Pub. no. 473:111, 112, November 20, 1936:

Type.--Female, adult, skull and lower jaws lacking zygomata, right P2 and incisors, no. 12432, Amer. Mus. Nat. Hist.; from Conard Fissure, four miles west of Willcockson, Newton County, Arkansas; obtained sometime in the period 1903 to 1905 inclusive (see plates 8, 14).

Range.--Known only from the Pleistocene deposit in Conard Fissure, at the type locality in northern Arkansas.

Description.--Skull.--Male (based on nos. 12437, 12441 and 12444): See measurements and plates 7 and 8; weight, unknown; basilar length, 38:1 (36:6-39:2); length of tooth-rows more than length of tympanic bulla; breadth of rostrum measured across lacrimal processes less than a third of basilar length; interorbital breadth ordinarily equal to distance between glenoid fossa and posterior border of external auditory meatus; zygomatic breadth probably averaging approximately the same as distance between last upper molar and jugular foramen.

Female (based on nos. 11766 and 12435): See measurements and plates 8, 12-14; weight, unknown; basilar length, 34:0 (32:5-35:1); length of tooth-rows more than length of tympanic bulla; breadth of rostrum about equal to (more or less than) 30 per cent of basilar length; interorbital breadth less than distance between glenoid fossa and posterior border of external auditory meatus; zygomatic breadth probably less than distance between last upper molar and jugular foramen.

Comparison of the cranial description given above with those of the American races of erminea from the far north will show that many characters are held in common--more than with more southern subspecies of erminea.

Remarks.--The ten specimens studied by the writer fall into two groups of six larger individuals and four smaller. Upon comparing these with each sex of the three species of American Recent weasels, frenata, erminea and rixosa, it is seen that size, and to some degree shape, rule out of consideration both sexes of rixosa and also males of frenata. Thus we are left with females of frenata and males and females of erminea. So far as size is concerned, it can be assumed that the larger specimens are females of frenata and that the smaller are males of erminea. This assumption has in its favor also, the fact that the postglenoidal length of the skull accords with that in Recent specimens. The difference in this regard in Recent animals is that the postglenoidal length of the skull, expressed as a percentage of the total (condylobasal) length of the skull, amounts to:

in frenata in erminea ordinarily less than 46 ordinarily more than 46 less than 47 more than 48

In the fossils the percentage for the larger skulls is 46; for the smaller skulls it is 48.

It may be that the ten fossil skulls are six female frenata and four male erminea but I think not. In the first place a skull of different shape, seemingly of the frenata stock, is known from the deposit and it is almost certain that two subspecies of the same species would not occur at the same place at the same time. It is possible, of course, that parts of the deposits were laid down at times so far apart that a shift in geographic range of two subspecies had occurred. This one skull, seemingly of the frenata stock, is the type of Putorius gracilis Brown (see p. 404) and was regarded as the only known specimen of gracilis. Regardless of the specific identity of this one specimen named gracilis, the chances of obtaining otherwise from a deposit, like that in Conard Fissure, six females of frenata and four males of erminea without a male frenata or a female of erminea coming to light are so slight as strongly to incline me to the view that the six larger specimens are males of the same species to which the 4 smaller specimens belong. By either this interpretation, or the one initially considered (of female frenata and male erminea), the animals from the fissure are at least subspecifically distinct from any American Recent weasel. Furthermore, by this latter interpretation each sex of this weasel, angustidens, is intermediate between the frenata and erminea stocks in the feature of postglenoidal length which feature, at any place where the two Recent species occur together, serves to distinguish one from the other. In the northernmost subspecies of erminea (arctica for example) the postglenoidal length in some males is no longer than in males of frenata. Considering general size, angustidens agrees better with erminea than with frenata and this circumstance has influenced me to place angustidens as a subspecies of erminea.

Today, erminea is not known to occur nearer Conard Fissure than northern Iowa, more than 400 miles to the northward. In comparison with the race there, bangsi, males of angustidens are of approximately the same size but in the shorter distance between the glenoid fossa and anterior margin of the tympanic bulla, and also in the lesser postglenoidal length of the skull, angustidens resembles the northernmost American subspecies of erminea. Females of angustidens differ more from any living weasel than the males do. The females are much larger than those of bangsi, and among living American races of erminea most closely resemble intergrades between arctica and richardsonii which intergrades are found approximately 1700 miles to the north of Conard Fissure. In females, the preorbital part of the skull in M. e. arctica is broader and in M. e. richardsonii narrower than in angustidens. If it seems strange that females of angustidens resemble one subspecies whereas males, in size, resemble another subspecies almost a thousand miles distant, it should be remembered that the degree of sexual dimorphism varies much from one subspecies to another in the Recent animals. An example is furnished by Mustela erminea fallenda and Mustela erminea invicta.

The assemblage of mammals from Conard Fissure includes several species of boreal predilections which, like Mustela erminea, now occur only much farther north than Arkansas. At one time the edge of the sheet of ice was only about 200 miles north of Arkansas. It may be significant that the cranial characters of the female ermine from the Fissure, and qualitative cranial characters of males from there, are most nearly approximated among Recent weasels by those which live along the southern edge of the frozen tundra.

In view of what has been said, the possibility should be considered that the distinctive cranial features of angustidens may be the result of evolutionary change in time as well as of geographic variation resulting from horizontal placement.

=MUSTELA RIXOSA= (Bangs)

Least Weasel

(Synonymy under subspecies)

Type.--Putorius rixosus Bangs, Proc. Biol. Soc. Washington, 10:21, February 25, 1896.