Descriptions of two new muskrats

Vol. XXllI, ^pp. 1-2 February 2,

1910

PROCEEDINGS

OFTHE

BIOLOGICAL SOCIETY OF WASHINGTON

DESCRIPTIONS OF TWO NEW JNIUSKRATS.

BY

X.

HOLLTSTER. \<^

^.

A systematic study

^{of the}

muskrats

discloses

two unnamed

subspecies,

preliminary

descriptions ^of

which

are

herewith

presented.

Both new forms

are

based upon specimens

ⁱⁿ

the

collection of

the United

States Biological

Surve3^

Fiber zibethicus

mergens

subsp. nov.

Type from ^Fallon, Nevada. No. _156,880X1. S. National

Museum,

^Bio-

logical Survey Collection. 9 adult, skin

and

skull. April 3, 11)08.

Collected

by

^S. E. Piper.

General characters.

—

Differs tromF. z. osoyoosensis ^{in its}

much

paler color

and

distinctdorsal _stripe,

and

from F. z. pallidus ^{in its} large ^size

and

darkercolors.

Color.

—

Fresh _pelage:

Above

_grayish

brown;

^head

and

dorsal area blackish; cheeks, shoulders,

and

sides rusty; underparts

creamy

^white withcentralarea pale

cinnamon

^or russet; usual spot on chin blackish brown. Fallspecimens ^{before the} black hairs have

come

in are some- times quite rusty above.

Worn

or

washed

out pelage:

Above

uniform pale yellowish

brown

; sides

and

underparts with^littlerusty.

Cranial characters.

—

Skull smaller than that of osoiioosensis, with shorter rostrum,

more

broadly spreading zygomata,

and

heavier _jugal;

much

_largerthan ^thatof pallidus.

Measurementsof type.

—

Total _length,540; ^tail vertebrae,240;hindfoot, 76. Skull: Basal length, 61.6;zygomaticbreadth,40; palatallength,39. o;

lengthof nasals, 21^; breadthof nasals, 9.8; alveolar length^ofupper molar

series,15.5.

Remarks.

—

Fiber z. mergens ^is a pale form of the osoyoosensis type, occupying^the northern_partoftheGreatBasin. There^is

no

evidence of directintergradation with the very ^differentpallidus onthe south.

Fiber zibethicus zaiophus subsp. nov.

Type from Becharof Lake,^Alaska. No. 131,488U.S.National

Museum,

BiologicalSurveyCollection. Skin

and

skull. October, ^1903. Collected by^A.G.

Maddren.

1—

Proc.Biol. Soc.Wash., XXIII.1910. (1)

2 Hollister

—

Descriptions of

Two New

Muskrnts.

General characters.

—

Tail short; hindfootsmall; ^skullwith

zygomata

not broadly spreadinganteriorly; molarssmall.

Color.

—

Fresh _pelage: General tone of upperparts bistre, darkest on back

and

_hips, with littleor

no

rusty coloring; ^{sides like} back,but with a slight russet tinge;

brown

_spot on chin reduced to a

mere

streak.

Underparts

creamy

^{white witha}

cinnamon

wash, varying^initsintensity,

and

_shading towhite on throat

and

hind legs; lips whitish.

Worn

^or

washed

out pelage: Upperparts ^{russet to} cinnamon, varying greatly ⁱⁿ thespecimens^athand, butusuallyshowing

much more

red thanin fresh coat, or in

any

pelage^{of F. z.} spatidatus.

Cranial characters.

—

_Skullwith

zygomata

^not broadly spreading ^ante- riorly as inspatulatus; rostrum

and

nasals longer; parietals very small, squamosalcovering

most

of area of braincase, even in

young

animals;

interorbital ridgeextreme ⁱⁿ development ^into a blade-like crest; teeth small.

Measurements.

— The

seriesfrom _{the type} locality

was

receivedwithout fleshmeasurements.

The

_lengthof hindfoot ofthe_type,takenfrom the dry specimen, ^{is G6.}

Four

adults from

Lake

Clark

and Cook

Inlet, Alaska, measured in theflesh,average: Total length, 533; ^tailvertebrae, 228; hindfoot,69.7. Skulloftype: Basal length,60; zygomaticbreadth, 38.3; palatallength, 38.3; length of nasals, 20.9; breadth of nasals, 9.2;

alveolar length ^ofupper molarseries, 14.4.

Remarks.

—

Fiber z. zalophus ^is a well

marked

form _{easily separated} from_spatulatus

by

^aniimberof constant characters. Itrangesfrom the Alaska Peninsulatothe

Cook

Inlet region.

y