The Florida muskrat (<I>Neofiber alleni</I> True)

V.-THE FLORIDA MUSKRAT (NEOFIBER ALLENI, TRUE).

Bv FrederickW.True.

lu the

summer

of 1884I

made known

forthe first time the charac- teristicsof a peculiar rodent, a singlespecimen of which was received from Florida iu

December

of thepreviousyear.*

No

additional speci-

mens

of the animal have been thus far received, nor

any new

informa- tion regarding its habits and distribution. It is mj- purposein this paper simply todescribe in detail the superficies

and

skeleton of the original specimen

and

to discuss its*generic

and

specific characters.

The

typespecimen

was

procured by William Wittfeld. ]*lsq., a corre- spondent of the Smithsonian Institution, inthe vicinity of Georgiana^

Brevard County, Florida. Georgiana is situated on Merritt's Island^

at the northern extremity of Indian River, nearly opposite

Cape

Cana-

veral.

The

islaud isabout35 milesin length from northtosouth,

and some

5 or C miles iu breadth at the widest part. It isse])arated froni the mainland

by

a straitabout 5 milesiubreadth.

The

collection inwhich the round-tailed

muskrat was

found con- tained representatives of

Mus

rattus,Hesperomys hucopus,ScalojJS acpiati- CMS,and a speciesof Sorex.

Neofiber,

True.

Xeojiber, Science,iv, 75, p. 34,July11, 18d4; Proc. U.S. Nat. Mus., ^vii,p. 170,July

29, 1884.

Form, arvicoline. Tailnearly as long as body, terete, nearly naked Hindtoes inalinewith themetatarsals, scarcelywebbed.

Thumb

with a claw.

Anterior cusps of molars roundedinteriorly, acute externally. Last lowermolar with 4 cusps, re-entrantangles alternating.

Parietals widest iu front, but with an angular i)Ostero lateral exten- sion. Interparietal wider than long. Surface of mastoid not dee]>ly:

concave.

Pelvis and pes not longer than skull. Transverse processesof luin-

•Science, iv,No.75,July11, 1884,p. 34. Proc. U.S.Nat. Mus.,vii,1884, pp. 170- 172(Julv29).

325

326 REPORT OF NATIONAL MUSEUM,

1884.

bar vertebrae short; those of the caudal vertebrae,except the firstfour, rudimentary. Vertebrae^: C. 7^; D. 13_; L. 6; S. 4; Ca. 25

=

55.

Neofiber

A.LLENI, True.

2\'eofiberAlleni,True, Science, iv.No.75,1884,p. 34; Proc.U. S.Nat.Mus.,vii,1884, p. 170.

A ^muskrat

of less than half the size of Fiber zibethicus^ butof the

same

general form.

Eyes

small

and

high

up

on the head. Ears mod- erate, broad

and

rounded, hirsute within the conch, the longest hairs extending0.8"™ beyond the margin. Borderof theconch slightly

and

unevenly notched. Fore feet as in F. zibethicvs.

Palm

black, except the

two

large posterior tubercles

and

the base of the thumb.

Hind

feet moderate, not equaling twice the length of the fore-feet. Soles naked, smooth, black,

and

5-tuberculate.

The

posterior internaltubercle large

and

ovalin outline.

The

remain- ing four,situatedrespectivelyattheanglebetweenthe1stand 2d toes,

between the 2d

and

3d, between the3d

and

4th,

and

between the 4th and 5th; all small

and

of equal,size. Soles narrow. Toes not in- clined laterally at an angle with the sole. Fringe of thetoes

and

sole not extendingi)rominentl3^belowthe plane of theirlower surface.

Toes of thefore

and

hind feet only slightly webbed. Claws horn- colored. Tailround,about ^0.6'=™ in diameterat the base

and

tapering gradually to the tip. Sparsely clothed with short blackish hairs, be- tween whichthetailappearscovered with rows ofscales, asin Mus.

Color of the hairof thebody above as inF. zibethicus; richrufous at the upper two-fifths

and

lead-color at the base. In a small area just behindthe shoulders the base of thehairs is white. Color of thehead the

same

as of the body, but darker. Hair of the under surface of thebody light rufous at the upperthird, lead-color atthebase. Chin, throat,

and

inner side of thefore

arms and

legs white or butfaintly tinged withrufous. Fore

and

hind feet aboveclothed with short,dull,

brown

hairs, which extendto thetips of the toes.*

Throughout its entire structure the Florida muskrat displays an

affinity to Fiberon the one side

and

to Arvicola on the other. It is strictly intermediate betweenthe two genera.

In generalshape theskulldeviates in no

manner

from that of Fiber.

The

lachrymalpitisless inflated inNeofiber

and

the nicking of the root of the

zygoma

in front lessobvious.

The

interorbitalareaislesscon- stricted posteriorly,itssides beingnearlyparallel.

The

squamosalsare

much

smaller than in Fiber,

and

do not approach so nearthe

median

line anteriorly.

The

parietals, on the contrary, are large, and, taken together, heart-shaped, the apex turned

backward and

truncated.

There is a small, regularlytriangular, j)osterolateral extension.

The

interparietal is broaderthan long.

The

zygomatic arches aresimilar

*This descriptionisa repetition of thatgiven in the Museum Proceedings(I.c).

FLORIDA MUSKRAT. 327

tothose of Fiber.

Between

the maxillaryand squamosal processesex- ternally the malar ^isreduced to a mere thread, as in that penus.*

The

strai)-sha[)ed process of the squamosal bounding" the squamosal fenestra stands nearly,vertically,

and

the constrictioji of the skull be- tween the fenestr?e is less than in Fiber.

The

anterior margin of the mcaiuHauditoriusis

much

lessprolongedthaninthat genus.

The

bullae aremoreintlateil.

The

surfaceofthemastoidisuneven, but not strongly concave; the foramen ver^- small.

The

coronoid process of themandible is not as high as the condyle, but the

jaw

isnot otherwise different from that ofFiber.

The

^anterior upper molar has fivecusps, the first not wider than the other, nor compressed.

The

second molar has fourcusps, the anterior largest, acute externally, roundedinternally.

The

posterior molar has fourcusi>s,the anteriorlike thatof the preceding tooth,the second

and

tliird equal in size,the last half-halberdshaped,

and

almost or quite external tothe

median

lineofthe series.

The

anteriorlower molarhas seven cusps, the first irregularly halberd-shaped, the last almond- shaped, the rounded end internal.

The

second tooth has five cusps.

The

^last has four cusps, ofwhich thefirst three are very small and the last rhomboidal.

The

skeleton presents a numl)er of peculiarities, aside from propor-

^tions,which distinguish itfrom thatofi^.zibethiciis.

The

inferiorlam- ella ofthe transverse process of the sixth cervicalvertebrais short

and

broad,

and

does not extendbac^ under the head of the first rib, asin F. zihcthicns.

The

neural spines of thedorsal vertebraeare

much

higher than those ofthe lumbar vertebrae,the reversebeing trueinthe case of Fiber.

Of

the sixsegmentsofthesternumthefifth isthesmallest,being one-half as high as broad. Tlie transverse processes of the lumbar vertebraea:e short,

and

do not extendto the levelof theundersideof the centra.

The

processes ofthe caudalvertebrae, after the fourth, are ludimentary; the vertebrae themselves are

much

elongated.

The

anterior extremity presents no special distinguishing character-

istics. In the pelvis the acetabulum issituated at thejunction of the third

and

fourth fifthsof its length. There isless difference in the os- seousstructure oftheieet ofthe two muskrats than one wouldsui)i)Ose

from an examination oftheexterior.

The

peculiarbendingof the toes in Fiber appears to be due to muscular and ligamentary antagonism rather than to any peculiaritiesin thearrangement ofthe bones of the foot. In Ncofiber the fifth metatarsalis not

more

than one-half as long as the second,

and

the first is but little longer. In Fiber the second

.

—

*

"Mr. N. P.Scndder(Proc.Biol.Soc.Washington,ii,ld85, p.Ixivjveryjustlytakes exceptionto Dr. Coues'sstatementthatinFibertbesquamosal ami maxillary spurs areincontacton the outersideof thezygomaticarch(Monogr.N. A. Rodentia,1677,p.

253). Such an arrangementof"partsappearstoexistonly incxctptional cases, ifat all. Amongelevenskulls inthe Museumcollection there arenone inwhichthe two spursareabsolutelyincontact,though inonethe spacebetweenthemisexceedingly narrow.

328 REPORT OF NATIONAL MUSEUM,

1S84.

toe is shorterthan thethird, and thethirdthan thefourth. InNeofiher the thirdis the longest, followed

by

thesecond

and

fourth.

In external appearance the Florida muskrat

somewhat

resembles Arvicola anipMhius, butit is easily<listinguished

by

itslargerhead and

feet, longer

and

less hairy tail,

and

heavier body.

The

muzzle isen- tirely hairy, except the small nasal pads.

The

eyes are noticeably nearertothe ears than to thenose.

The

ears are not entirelyhidden

by

the surroundingfur.

The

fore

ami

hind feet are pilous above

and

naked below.

The

palms bearfour tubercles, as in Fiber zibetliicus.

They

are black, except the

two

large posterior tubercles

and

the base ofthe thumb.

The

narrow soles aresmooth, black,

and

quinqui-tuber- culate.

The

posterointernal tubercleislarge

and

ovalinoutline.

The

remainingfour aresituated intheintervalsbetweentheaxilsofthe five toes.

They

are all equallysmall.

The

toes

when

flexed do not lie across the sole,as inFiber ; thefringe ofthetoes

and

soledoes not ex- tend noticeably belowthe plane oftheirlower surface.

The

tail isperfectlyterete,andsosparselyclothed withhairsthat the scalesare distinctlyvisible.

In general color the Florida muskrat does not differ greatlyfrom Arvicola amphibius, butthe hair is

more

likethat ofFiber.

On

theup- per surfaces^itis plainlyof

two

sorts.

The

under-furis soft

and

crenu- late, notglossy,

and

lead-colored,except atthe terminal fifth. Mingled, with itare

numerous

stiff,shininghairs,abouta halflonger,

some

being dark atthetips and others golden.

Xhe

dark-tipped hairs prevail on the back,butare

outnumbered

on thesides

by

thelighter ones. These long, glossy hairs are sufficiently

numerous

to give the

back

a decided sheen,butnotsuch asis seeninwinterspecimensofFiber.

The

fringe overhanging thelips is

composed

of

opaque

whitehairs,but the short hairson themargin of thelip aredark.

The

whiskers aredarkat the base and lighter at the extremity.

None

arelong enough to reach the ears.

The

ear-conch isclothed externally

and

internallywith shortfur likethe underfur of the body. In the

median

line of the back, just abovetheinsertion of the tail, boththe underfur

and

hair are very long, forming a sort of

mane

or crest.

The

hairs of thetailaredark

and

about one-fourth inchin length : the terminal pencil isvery small.

The

fur of the under surfacesis short,

and

attheextremityitscolor isverylight fawn.

The

extremity of the under

jaw

alone is darker.

The

lower two-thirds of the under-fur ^is lead colored, the extremity fawn-colored.

The

stifferhairsaredarker

and

nearlytwice aslong. (Jn theexteriorof thefore feetthefur is like that of thesides, internally likethat of thebelly.

The

long hairs extend

down

the leg

and

there is adistinct tuft at the heel.

The

color of the appressed hairof the feetis that ofthestiffhairs ofthe sides.

On

thehindfeet

and

legs the colorofthe hair is the same,but there arefewer long hairson the legs.

The

colorof the claws islight.

FLORIDA MUSKRAT. 329

Meaturementa ofKeofiherAUeni,from^{thetypicalalcoholic}specimenfromOeorgiana, Fla.

CentimetcrB.

Lengthofheadandbody 20.2

Lengthofhead 5.2

Lengthoftail 12.

6

Lengthofhindfoot(withoutclaws) 3.&

Lengthofforefoot(withoutclaws) 2.3

Nosetoeye 2.0

Nosetobase of ear 4.5

Heightof ear 1.8

Lengthofmiddletoeoffore foot(withoutclaw) J>

Lengthofmiddletoeofhindfoot(withoutclaw) 1.0

Longestclawof fore foot 5

Longestclaw ofhindfoot 6

Measurements ofthe skull.

Totallength 4.7

Greatestwidth 2.9

Lengthof nasals 1.2

Lengthoftooth-row 1.

1

Front edgeoffirstmolartoposteriormarginofincisors 1.6

Greatestwidthofmuzzle 7

Widthofiuterorbitalbridge 5

Centerofoccipital crestto lineofhindermarginoforbits 1.9 Measurevients of^{the skeleton.}

Total length(along curves)

Anteriormarginatlas toextremity of post-zygapophysis oflastsacralvertebra.

Extremityof post-zygapophysis oflast sacralvertebratoendoftail

Lengthof7cervicalvertebrae Lengthof 13dorsalvertebrae Length ^of6lumbarvertebrae Lengthof4sacralvertebrae Lengthof 25caudalvertebrse

Lengthofscapula (glenoidfossatosuperiormargin) Lengthofsternum (withoutensiformcartilage) Length^ofhumerus

Lengthofulna Lengthofmauus Lengthofpelvis ,

Length offemur Lengthoftibia

Lengthofpes

32.8 12.9 15.2

L6

5 3 6 2.7 15.2 2.4 3.2 2.6 3.3 2.1 4.5 3.3 3.8 4.2

Tlie characterswhich have been

employed

to separate Arvicola

and

Fiberrelateto the feet, the tail,and theposterior lower molar.

They may

be contrasted thus

:

Arvicola.

Tailterete.

Hind feet not specially modified for aquatic progression.

Posteriorlowermolar withthreecusps;

the re-entrant anglesopposite.

Fiber.

Tailcompressed.

Hindfeetgreatly modified.

Posterior lower molar withfour orfive cusps; the re-entrant anglesalternate.

330 BEPORT OF NATIONAL MUSEUM,

1884.

Upon

the discovery of a

uew

form having a terete tail, simplefeet,

•

and

four cusjis in theposterior lower molar, there-entrantangles being alternate, the question at once arises as to thevalidityof thesechar- acters as generic distinctions. In introducing Neofiher into the sys- tem several x)laus areopen foradoption.

The new

form might be

made a

subgenus underArvicola

by

degrading the characters

drawn

from thelast lowermolarto subgeueric rank.

On

the otherhand, it could beintroduced as a subgenus, or even species, under Fiber

by

degrad- ing the characters derived from thetail

and

feet in the

same manner

to subgeneric or specific rank. Again, the genus Arvicola might be enlargedtoincludeArvicola, Neofiher,

and

Fiberassubgenera. Finally, the round-tailed

muskrat

might be

made

thetype of a

new

genus in-

termediatebetween Arvicola

and

Fiber.

The

last-mentionedcourseis,to

my

mind, themostsatisfactory,

and

I

have

therefore adopted it.

With

the present absolute incommensura-

bilityofgenera, Isee noespecial advantages, except in certain extra- ordinarycases, in introducing a gradebetween genus

and

species.

On

the other hand, no one probably

would

seriously considerthe proposi- tion of placing Neofiher as aspecies under Fiber.

One

can conceive, hovvever, of the existence of speciesof the latter genus which should differ from F. zibethicus in proportions, quality

and

color of fur, web- bingof the toes,

and

othersimilar details ofstructure.

Itis

somewhat

remarkable that a rodentsolarge as Neofiher should

have

remained

unknown

to

American

naturalists untilthepresent. It is true that exploration has not been so activein Florida as in

some

other parts of the country, yet the State hasbeen traversed

many

times

by

observantnaturalists

and

collectors.

One

feels convinced that the species

must

be very rare oris confinedstrictly to alimited area.

The

former opinion

would

appear to be the correct one, sincethe locality

from which the type specimen

came

is afavorite resort forsportsmen,

some

oneof

whom must

have recorded the species were it veryabun- dant.

What

the habits of the Florida

muskrat

are can be learned only fromfuture observations.

The

structure of the animalwouldlead one tobelievethatitisnotsothoroughly aquatic as F. zibethicus.

UeportNat.Mus.li-S4.-Trne. FloridaMuskrat.

PLATE

I.

^

?.

2 O

PLATE

II.

NeofiherAllciii,True.

—

Type.

Fig. 1. Skull. Viewfromabove,

X

^1.

Fig.2. Skull. Viewfrombelow, X^1.

Fig. 3. Maudible. Rightside,

X

^1.

Fig. 4. Rightsuperior molars,

X

^4.

Fig.5. Rightinferiormolars,

X

^4.

Fig. 6. Frontfoot,

X

^1.

Fig.7. Hindfoot,

x

^1.

Keport. Xat.Mus.1884.— True. FloridaMuskrat

PLATE

II.

Fir,. 3.

Fic. 5.

Tui.4.

Fig.

KeofiberJUcni, True.

PLATE

III.

Fiberzibethicns,(Liuud).

Fig. 1. Skull. Viewfrom above, X^1.

Fig.2. Skull. Viewfrombelow,

x

^1.

Fig. 3. Mandible. Rightside,

X

1.

Fig. 4. Left superior molars,

X

^4.

RepoitXat.Mus. i884.-Truo. ^FloridaMusUiat.

PLATE

^III.

Fig.4.

FIG. 1.

Fui.^.i.

Fig. ^2.

FiberzibtthicK^,(Liund).