Description of a new rodent of the genus <I>Idiurus</I>

Vol. _XII, pp. 73-76

March

_24, 1898

PROCEEDINGS

OF THE

BIOLOGICAL SOCIETY OF WASHINGTON

DESCRIPTION OF A NEW RODENT OF THE GENUS IDIURUS*

BY GERRIT

S.

MILLER,

^JR.

Among ^some

African birds recently

purchased by ^{the United}

States

National Museum were found

a

few mammal

skins

from

Efulen, ⁱⁿ the

Cameroon

district.

Two

of these are referableto the

rodent genus

^described

by

^Mr.

^{Paul Matschie} under

the

name

Iiliurns.j

Although taken within seventy

^{miles of}

Yaunde

Station, the

type

locality of Idiurus _zenkeri, these

specimens

^are referableto a species quite ^distinct

from

the

one

represented

by

Mr. Matschie's

unique

type.

The new ^form may ^be

^called:

Idiurus macrotis _gp.

now

Type No.83625, United States National

Museum, $ young

adult, ^col- lected at Efulen,

Cameroon

district,

West

_Africa,

June

_{18, 1895,}

by

^G.L.

Bates. Original No. ^4.

Generalcharacters.

— _Much

_largerthan Idiurus zenkeri.Matschie; tail

and

ears relatively longer; ^colorapparentlydarker;skull larger;

bony

palate narrower; secondlower molardistinctly largerthan first.

/•'///andcolor.

—

_Pelageformedofhairsoftwokinds.

Main body

^offur

composed

^ofsoftdensely^{set hairs}about9

mm.

in length. Interspersed with these are hairs about double as long and _closely resemblingthose of thewrist

and

foottufts. These hairsoccuronthe dorsal surface only, andaremost

numerous

_{along the} sides. Dorsal surface of

membranes

coveredwithfur

somewhat

lessdensethanthat

on body

^{; extreme}edges of

membranes

bare. Ventral surface of

membranes

very sparsely haired.

Distribution of hairontail

and

feetexactly^asdescribed in/. zenkeri.

*Published bypermission of the Secretary of the SmithsonianInsti- tution.

tSitzungs-Berichte Gesellschaft Xaturforschender Etvuude ZU _Berlin, 1894, p. 194.

16-Bjol. Soc_Wash., Vol. XII.I§9S ₍₇₃₎

71 Miller

—

Description of

a New Rodent.

Fig.1."'.

—

Frontfootof Idiu

rusvine rotis. (X1/^-)

Colorabovesepia, slightlygrayeron _posterior halfof back,

and

dark- ening ^to nearly black on

membranes. A

_faintly indicated dark _stripe from base of earto muzzle. This is perceptible ⁱⁿ certain lights only.

Throughout ^the

body

^{furthehairsare} dusky

plumbeous

^towithin about

J iniii. of _tip. This darkercolor appearsevery- whereirregularly atthe surface. Ventral surface pale yellowish

wood

_brown, irregularlydarkened

by

^the

plumbeous

bases of the hairs. Hairs

on

under sideof

membranes

_{very dark}

brown and

with

none

ofthesilvergrayappearance^described inI.zenkeri.

Dorsum

of

manus

andpeswith_{short,scattered,}dark

brown

hairs. Fringeonwrist_{(rig. 15)}

and

sideofhindfootdark brown. Tail darkchestnutbrown, slightly tinged with _yellowishnearbase.

Feet.

—

_{So far} ascan be determined from dryspecimens, the ^feet are essentially as^in"Idiuruszenkeri.

The

frontfootwithitsequaldigits,rudi-

mentary

thumb,

and

fringed ^{wrist is}

shown

_{in figure} 15.

Tail.—

The

generic characters of the

tail, as described

by

^{Mr. Matschie in}

the type of Idiurus ^zenkeri, are exactly reproduced ^{inJ. macrotis (fig.16).}

The

pad of projecting^scales occupies^aspace about 17

mm.

ⁱⁿ length

and

4

mm.

in width.

The

_proximal

end

of the pad

isabout 25

mm.

behindthe anus.

The

lateral fringes begin

on

each sideof the proximal end ^{ofthe scale pad,} but the ventral fringe reaches only ^{to a} point about 15

mm.

behind the pad.

The

three fringes continue distinct to near the tip of the tail, where the hairs of which _they are

composed

gradually ^be-

come

longerand finally blend with the long sparse ^hairs of the dorsal surface to form the terminal _pencil.

The

hairs of all three _fringes are about 4

mm.

in length, those of the ventralfringe closely appressed.

Long

^{hairs on dorsal sur-}

faceoftail 30-4o

mm.

in length.

Ear.

— _The

ears (fig.17)are

much

largerthan in1.

zenkeriand wholly naked both ^within and with- out, except on the external basal third, which

iscovered with ^fur similar to that of the head.

With

a lens a few very ^{small hairs}

may

^{be de-}

tected on the anterior border, but these are ^in- visible to the unaided _eye. In form the ear^is very simple

and

strongly suggestive of that of

Fig.10.

—

_{Base oftail} Iunder sidei of Idiurus macrotis. (X!%•)

Fig. 17.

—

EarofIdiurusma

crotis. (Xiya.)

Description of^a

New

Rodent.

75 some

of the smallerbats. Nearthe base oftheauricleon the innerside arethree welldeveloped cross-ridges,

and

a fourth which islessdistinct, Skull.

— Th*

skull _{(fig. 18)}isingeneral similar^tothat of Idiurus^:<

nh

^ri.

The

_{bony palate, however,} is at its widest point scarcely wider than the first molar, whileatits narrowest point^it

isdecidedlynarrower thanthis tooth. In I.zenkerithe palate

isabout doubleaswideasthe toothrow.* Surfaceoffrontals slightly and evenly convex, with _scarcely a trace of the six protuberances

mentioned

in the description of^/.zenkeri;

orbital edges knifedike

and

slightly overhanging. ^Incis- ive foramen a narrow slit, ¹

mm.

_longand aboutone-third as wide.

Mandible _very short and deep, the greatest depth ^con- tained only one and one-half timesin greatest length. Cor- onoid process joined with^artic-

ularprocess bya thick bridge ^{FlG- Ls}-~Skull of Idiurus macrotis. (X1%).

below which the bone is thinand semitransparent,butnot fenestrate as in the type^{of/. zenh}ri.j

Teelh.

-Upper

molar rows _slightlyconvergent anteriorly.

Combined

iength of three true-molars _equal to anteropos- teriordiameterofincisor. Premolar about three- fourthsas large as ^first molar, which is the lamest upper ^tooth. Second molar _distinctly smaller than first and abouttwiceas large as third.

The

crownsof thepremolars

and

thefirst

and

second

c3dJ>/'7 molars are each crossedby tworidgesof enamel,

isolating three narrow depressions, the posterior ofwhichissonarrowas to bepractically invisible totheunaided eye (fig. 19, a). Third molar with one _ridge

and

two depressions ⁱⁿ the _type,

two

ridgesandthree depressionsⁱⁿanolderspecimen with _very

much worn

teeth.

First

and

second lower molars (tig. 19, b.) essentiallyequalⁱⁿsize,but second _slightlythelarger. Thirdmolarconsiderably smallerthan second

Fig.19.—TeethofIdiurus macrotis; ^a upper, ^b lower. (X1%.)

*"

Gaumenbein

fastdoppelt^sobreitwiedieZahnreihe . . ."

t

The

fenestration in/.zenkeri

may

^{be due to} injuryduring prepara- tionofthe specimen.

76 Miller —

Description of

a New Rodent.

andabout equal ^topremolar.

Enamel

_patternessentially as inthe

max-

llary teeth, butlessregular.

General remarks.

— _The

type of Idiurus zenkeri is an old*adult female

i

"'

cm

sehr altes W-eibchen _"), while thetwo specimens^{of1. macrotis are} males, one

young

^{adult, the otherold. Yetthe} differencesbetweenthe two forms are too great ^to be ascribedto sexualvariation.

That two

or

more

_speciesof agenus ^sopeculiar^asIdiurus should occurinthe

Came-

roon districtis not at all improbable. Neither can it he'

wondered

at thatanimalsso perfectlyprotectedby^color

and

form _{(thegeneralappear-} anceis well

shown

in Mr. Matschie's _figure) should successfullyescape notice, especially^if,as isprobably^thecase,they^arestrictly nocturnal in habits.

Measurements of Idiurus ^macrotisand I.zenkeri.