560 PROCEEDINGS OF THE NATIONAL MUSEUM

Lecaneelegans.

Lecane hornemanni.

Lecanepapunna.

Monostylabulla.

Monostylaclosterocerca.

Monostyla cornuta.

Monostyladecipiens.

Monostylahamata.

Monostylalunaris.

Monostylaobtusa.

Monostyla pyriformis.

Monostyla quadridentata.

Monostyla rugosa.

Monostylavirga.

Lepadellacyrtopiis.

Lepadellatriptera.

Colurella bicuspidata.

Colurellauncinata.

Trichocerca pusilla.

Trichocerca rattus.

Diurellastylata.

Diurellatigris.

Diurellavoluta.

Polyarthratrigla.

Pedalia mira.

Collothecapolyphema.

Ofthe 109species anddistinct varietiesrecorded,46are

common

tothe Atlantic and Pacific slopes, 55 occur only on the Atlantic, and 8 onlyonthe Pacific slope. Thisgroup of 63 species includes but 20 occurring in sufficient

numbers

to be termed

common —

16 Atlanticand 4 Pacific species. Itisquestionablewhetherthesefig- uresdemonstrate anything

beyond

the already

known

lack of suit- ableenvironmentsonthePacific slope.

The

closely relatedgeneraLecane and Monostyla exhibit

some

inter- esting anomalies of distribution. Of the 13 species of Monostyla, 12 are

common

tothe Atlantic andPacific slopes; Lecane is repre- sented

by

22species,only7 ofwhichoccurinbothwatersheds.

Four

species of these two genera, Lecane amorpha, L.fiexilis, L.

tenuiseta, and Monostyla hifurca, to which

may

be added a fifth, Monostyla (

=

Diarthra) monostyla, found

by Daday

in Paraguay, occur onthe Isthmusinponds, while here atWashingtonthey are found onlyin

Sphagnum.

This change of habitat is withoutany obvious explanation; the reversewould have been

more

intelligible.

Ifonlyonespecies

had

beeninvolveditmight have beenpassedover, but

when

the

same

peculiarenvironmentalrelationisfoundtoapply to five species,there

must

be

some

definitecauseforit,whateverthat

may

be.

The

fauna of

Gatun Lake

at the time thecollectionswere

made was

practicallyanormal

pond

fauna,asdemonstrated

by

comparison withsimilar locahtieson the Isthmus. Rio Trinidad,in the region represented,

was

virtuallystagnant. Itissurprising to findsofew species

common

to these two connectedbodiesofwater.

The

lake faunawould beexpectedtobetransplantedfrom RioTrinidad; evi- dentlythisdidnotoccur,anditsorigin

must

have beeninthe small ponds which existed in the territorybefore the construction of the lakeand weregradually engulfed.

IftheIsthmian listiscompared with Mun*ay's ofthe collections

made by him

in Chile,Argentina,andBrazil,asufficiently close agree-

ment wiU

be found to warrant the conclusion that the rotatorian

NO. 2062.

NEW ROTATORIA FROM PANAMA— EARRING. 561

faunaoftheIsthmusisSouth American. Thisis merelycorrobora- tive ofthe reportsonother groups,which haveestablishedtheagree-

ment

oftheIsthmian faunaingeneralwiththatofSouth America.

The

twolistsrecorda total of 138species, ofwhich35areHmited to South and Central America.

As

both lists are fragmentary

by

reasonofthe nearlycompleteabsenceoftheilloricatespecies,a

more

accuratejudgment

may

bearrivedat

by

astudyofthegeneraLecane and Monostyla,in whichallthespecies are recognizable, even

when

contracted.

A

total of43speciesbelongingtothesetwogenera occur inthecombinedlists,21ofwhicharenot

known

outsideoftheSouth Americanfaunal regionand26species are

known

onlyfromthe

Amer-

ican continent. Naturallyboth Murray's andthislisthavetheirquota of rare species,but

many

of the exclusivelySouth Americanspecies areabundant,such as Lecanearcula,L.comjpta,L.crepida,L.curvi- comis,L. Tiana, L.pusilla, Monostyladecipiens, M.furcata, M.pyri- formis, M.rugosa,and

M.

virga.

No

doubt

some

^ofthesewilleven- tuallybe foundelsewhere,but onthe other

hand

itisat leastequally probable that

many more

undescribedspecies exist inSouth America, in viewof the limited territoryrepresented

by

thecollections, and the conclusion thatitisentirelypropertospeakofadistinctlySouth American^rotatorianfauna seemsthereforeirresistible.

The

locaUzation ofso

many

species of Rotatoriashouldgo far to disprove theimportanceofbirdsasagentsofdissemination.

No

one

win

ofcoursedenythat birdsdoinfluence distribution to

some

extent, butit isextremelydoubtfulwhetheritamountsto

more

thanequal- izingthefaunaofcircumscribed locaUties.

That

anylong-distance transmission takes placeisapurely gratuitous assumption; itisren- dered highly improbable, ^ifnotactuallydisproved,

by

thediversity of the rotatorian faunas of North and South America. It is well

known

thatourmigratorybirds winteronthe shoresoftheCaribbean andcountlessmillions

make

thetripeveryyear, sothat the rotatorian fauna ofAmerica from the Equator to the ArcticCircle should be sensibly uniform, ifbirds were even accidental carriers.

The

indi- cated greatdiversity oftheNorth and South Americanfaunasflatly contradictsthis.

Whileithas been frequently claimed that the Rotatoria are dis- tributedaUover theworldwithsomething approaching

monotonous

uniformity, the evidence

upon

whichthis assertionisbased appears entirelytoofragmentaryto

draw

anysuch far-reaching conclusions from.

And

it would be necessary to bring forwardirrefutable evi- dence, as a uniform, cosmopolitan distribution is

unknown

in

any

other subdivision oftheanimalworld. Itseemsparticularlyoutof placeinthe caseofthe Rotatoria,asit isin directopposition to the better

known

facts ofthedistribution oftheEntomostraca,whichas far as

we know

oughttobesensiblyparallel, at leastthe adaptation

34843°—Proc.N.M. vol.47—14 36

562 PROCEEDINGS OF THE NATIONAL MUSEUM.

^vol.47.

toand

means

for distribution are identical inbothcases. Ithaslong ago been demonstrated ^that

some

Entomostraca arecosmopohtan, while

many

are

more

orlesslocalized,and thereis every reason to believe that the

same

holdsgoodforthe Kotatoria.

A

majority of thespecies are,

upon

^the basis ofour present knowledge, limitedto particularlocalities. That ^this localization

may

be in

some

cases onlyapparentis obvious; thereis nodoubt that

many

animals

now

consideredrare willeventuallybe

shown

tohaveawidedistribution.

But

it should be evident ^{that, if}

we

begin

by

assuming universal distribution, it is unUkely that

anytMng

willbe discovered to dis- proveit,not only becauseitis not searchedfor, butalsoon account ofno attemptbeing

made

to correlatethe acquired evidence.

That

many

species ofRotatoriaundoubtedly doenjoy a world-wide distributionis certain. Thisis notsurprising, considering the great ageof thisgroup, which,evenifnot demonstrated

by

paleontological evidence,

may

reasonably be^inferredfrom the well

known

factthat the origin of Arthropods dates back to the unrecorded interval betweenthe Archaean andPaleozoic eras; thatallthe majordivi- sions ofthe lower Invertebrates originated long^{before the}appearance ofthe Artliropodsis

now

universally accepted,and ontliisbasisitis

notdifficulttoaccountforthe extensivedistribution of

many

species of Rotatoria. In thisconnectionit

may

not be outofplace tocall attentionto thefactthat the earhest

known

bird, ArcJiaeopteryx,is ofJurassic age,sothatifthe Rotatoria

had

been dependent on dis- tribution

by

birds, theywould have

become

extinct ages beforedis- persal could have occurred. It is also quite possible that bird migrations

may

beofcomparatively recent^origin.

Forthe reasonsgiven,itwould seemthat the universaldistribution theoryisat leastunsafeasaworkinghypothesis,ifnotactuallyharm-

ful.

A

^{carefulstudyof}the rotatorianfaunaofanylocahtywhatever

isstillworthwhile, until

we

havefar

more

completerecordsthan

we now

^{possess. Systematic work,} including faunal ^lists,

may

not be themostsatisfying tothe investigator,but botharethe foundation

upon

whichthewholestructure

must

beerected.

One

of the consequent drawbacks ^of the universal distribution theory^isthat

many

forms without doubt remainunrecorded,ifshow- ing acertainresemblanceto

some known

species.

As

partlyresponsi- ble for thisone

may

alsoconsider the imprecationssooften hurled at theheadofthe unfortunate

who

happenstogive a

new name

^to an oldspecies,surelyaminoroffense,provided thedescriptionandfigure arebothgood. It^isvery

much

easier to relegatea

name

to

synonymy

thantosiftout a

number

of species travehng underthe

same

name, and if merely fisted without description and figure it ^is obviously impossibletodetermine the identityoftheanimal whichthe observer

had

before him.

NO. 2062.

NEW ROTATORIA FROM PANAMA— EARRING. 563 The

crying need of rotatorian

taxonomy

is at present exact and

fulldescriptions ofallthe

known

species.

Too much

stresscannot be laid

upon

complete descriptions. Itis notsufficient to differen- tiate thespeciesfrom allothers

known

to-day. It is quiteevident that

we know

asyet only a smallfraction ofthetotal

number

of spe- cies of Rotatoria extant, consequently a description (and figure) should recordallthatcan beascertained in ordertoenable the future discovererofacloselyrelated animaltodecidewhetherhisspecimen belongstoanold speciesorisreallyanundescribed form. This should not be construed as disparaging comparisons with

known

species.

These are very useful, but should be only accessory.

Our main

dependence

must

be adetailedand fulldescription.

By

description is tobe understoodnot merely the

word

picture,butalso thefigure,

whichin the absenceof afixed terminologyis absolutely necessary.

It is indeed doubtful whether combinations of words will ever be sufficient to differentiateRotatoria withoutbeing supplemented by anillustration.