rene rah popper
rye har Wve mainlers ‘m
Hele HOO bt achoe |
by ’
Hoary laiaauepabed sara on pyatitct nie
nue 1, ue it a4
fi ; 4
ei esies heal avi
Wr
Hihy! Cc
Mat ‘ Haiti Mt ii
ata tsteta (!
Le
4 ate
V0 sh ieainiy
Hartt baad aah
read ae sala,
mee rh ghdi ate babes
“dL aatslaseraTG
i iad-4 ee ee
agile? ny Ui hae ai) ae
thas sins yaaa
Thin Nadohiae Seng ty hae
PAweerony gh No ar esaey ate
Ris ps adhe iarntierg:s + natea
* ni nt Rad rye
iN
Sd ATO a9 nye htyy
AT asmehsh oes Maes: ist
tlie Aba ‘ Ae vb 038
deny Hiner pOrey
We he \ ited te
. 6
iat ue eqs Ne
41a losate
rh act nN ait} i} havi)
A BRAT aires od
qi
tHe Hed st
ridredk Way
pet ty
Gl ee ha
Lanineds | hae pelt
ae Vea tat yo
W hy Vaasa th tus
His eradlenel. (age
RACAPASUEL PCIE Ads by ius 4h
rie Ave HH, a HF
teetwol a aay At
boy hy Tris
tas hegin rate
SEH) Wan died bs atg shea A Py neye st ‘ Nath >| ir’) Hy ey
WU EOTEST RC VRPT AC EY oat MeL A Hpk
MEN vaaye Larechet ain
ANG TR HAY
jana yy me anes
eMC:
Fn
vate 2 rekan a
Pray aie
HO ey it
pecs muvet Sere
welertath ate
att
arr
‘aha sani
1)
eta
aa "*
i ba iearase hand Leas
OT ry tres: aalee bd
Rprtshenspacd
‘- aes aso
sta
ye
‘
fh a
Wh ie
aA ai ae rit
Al 4 ‘ants
eta teali Hons han Oe
Hh ep ef erty be
‘
a)
wane Hs
Parry
Tia sua a it i
A MC thas Leikaw in opehe
ui sat pean 64 e
ny
at
‘4 (ie
pt waft
7 sane ys Cn |
TUTE et
i.
np}
a4
it . wit
Habib “4
My
ays
thik ites
116 ah
yee
itt mitt
tite wi Has
i uPyty ste
he HN aia it sah Ki} iM
H
4 qv ii ititiegs i beat
tat) Ge 4. re) Heel ny Tasos
A bee ed Mi
tH it
fash
ty 45 Foye neat
vied eye
cite
40 she
At
retire
pialiile
uae
Salita iy! Feds fy ta the
Lat tie intait
eis
4
Fy Ie esate
#4 oa
aint
Hiatt
Vilhed
nf HY {hel
ahi)
i
, oy
enh ieisil oes Rit
ARAM AAEM INR rst ih sa terete
r pHa hie wow
‘
Mk sede
mt iy {ined ith
i y ir ai eita Rta
Be? ih:
4 ait Shes neyeeitly ’
NOSATEAINO TA At bam UPD DNA A nb "ty!
Ete trie ho woke h Wee Feber rp
i (east ‘1 ee ti ie ot jt 4\4 ty
- ‘ mys rd
ghee Wiehe Hie Wi :
Nie : abbas avatas 1iGai ae
Dyas . ty
10) Bh abe A ee ET a
id heuaead a; ithe fine ah] iy
Patt iT)
Hees
uae
¥
Uele ud 1-° iid ae
4
Lise Mn ‘hia
i ele ‘ bed i} Hewedes
nett 118M TG i) aa i Ce tines . * ii “6
PMH isa at
Les, ilihegt:
ss
Neietpakeee
nin
wh
A atiaaittds DRIAL R bag nan
yitaaty rit Ҥ rau
ae
4 roy
yheitne AR ELE db Maal
‘ ry Wi i twa cbshves
as) RA)
aeile
beta Ly Heh |
He ula ahi pate
lew
ilavaaies tions |
es LLU AAL AAS (ian in
aa eerts
My } a i 4A
he Ds gnd py
nt bs bi F
4
(ibd W4 i th
need
a fe
dir bed) iV rh} tpl dimieanard
Memb iat Ht) Rta ei ale Vay i peys ay
HV CUAM OLA DE CAR ELAL URS}
Vay" bi twee nig sald i a Pr) 1) ney i)
Vy feaeigt dh ¥ Cort
“ral 1 yatiny
vary
‘4
Lean Hy Lay
jt rh CELLS (4 bay
ne “4 sa 70 a9 a yi ius
iW bape rhevr tie
\ Waitt ‘ an at
Ot ‘4
Prubivs th
cf ne aaa at
neue ite rye tied
‘ath 0 des se Pol
PN FH va ayaa
“ te ih Wiaite #4
ney wapeite revit Hit SCL tLan
‘i ett Webco akan ee
typ 4) eae See Mae!
f, ih tay pie alate Ve Py Win
: Lr) aon le mY, 1H Wh j wreiseng er?
tee eanidaw ny f
aeeer
’
oat id
NetaY tah ts
Sit Veawabyl ad Va eM eM a4 are cn
4) hy Wel rad eh nie dene nehdia Ay
lytwe palatal VA sane a4
rit i hye) eit Aine Hi tent
COPPA KLEE
Wy j har
AAR IN) aay
ates :
Hide vad tyveads abasic aah
Vrs ta od ey dire 7 ete het Fit
4 wt 4 fe
ie hac
‘0
adverataeunalas
way ‘ ry her | seus ey diate
rae “” iia: giatg Cre rt. qeeede eas
aeanialerda tit hohe ril vehi ht; bbar yO
del
SL he ee Th “4 Ney al ey pa ate
Wigiae ae tee a
4 ard A Fain ‘eyint a 1 H0 ane wie 4
a ‘ ps
patetey H felon Re
¥ #u \eayaiyy edie
Hii) dipety CQ iely
Vitimefr el euinel be
HRW yidet rte ia
Tah Webs Hie eg
RATE LCL Une salwre.
"4 byylads ir " 4
' Lane
Dsbedceagiaras
Vidseey ai A NegWi4s hate
as poalatatt
4 Bh lee fade 4)
Wa rtete Le Ate wi 4 er)
qe ape eg ne
Hart Pee diner tea tysasy silad ste fa
: la
Si kere ear wit wea an '
nt 430) i } a0 hee
~ sian
rare
Pha ted
mors fie ;
rt ’ Vem esalhe ttt ree
thebipiesa ae Tnsalaveet mh ' Liha) noes tii i a
02078. i tigi \ :! ity Leche eel see : : ee
14 Hh
ic
el haebinn) pea
vane ish dt
Hiatt thy te yi
ean ne Wi hie
ma ad arta de
Currie
+ trae ii
eters Wh caigeaidits an
iy? a serch tgie
, any Phdive\t
eat PUN
t tify i; ate o a
ny oi
feted hoa
see a! nyt Tititids v 5
itty Haines
it}
tata 14 4. eae: “i sata rit sy nth Hie
a nt ¢'
sheath
wer! Teptis
tai i
ran Hh
ad wei i
Sidil areal vy
‘i or i
Susie
Wh ain
Nason
Faineied)
Jin rH (int tt at
trends
t
ie yh tains :
aE 0.9 hy
bret ata se
ey SET
i hp
nh
ity
uni aya oe fit tH
a
EM HF)
ry
ae manne . rit " SHE HP Vitenant ta
Powe
Way? ahve
ay ON ai Dabes hated
h abetitnl,
Waa pad araly
jPoal Heitog
+4
Prt i Mare
eri yet ret bowen
:
Met
¢ ahh be }
oa 2! 9 Melee LT Va
facia int ‘ she ; any beeen) a tH Aa
sath nid ese rire ett wie is wy
Wis
Ay GY LC ivbheL ie
hee patel 4 ‘y
Hitt Spa even
“ i)
Matar pi eG :
opel
ae r fh ae) My oy
Wey Gt aE te rorgedeawedt | hay Rhanetag
Heras’ mitith
sq aaeu ara y teks Testa:
ararerandiastiataiscere %y sie f deghveseteny
‘ya
erir tl ‘ ey bs . a} '
(4) crt tile ih eh nila ory alacie ‘4 Sphesany jaf r| ie Ayedvee
4! Foe weaning 1 i
{4a mags Atte
rT hye
eaten
iit satus a Hina ity } Thay maine bell by ea
ig %
fice rey! CHTTrea rat ait iatntate
on ‘ .
vas CRE
14 Bethy
mat aA dad ort
wm,
y Raywiyes
as epeduniel sh ae!
Cal raat matt
) Seeeheevticdtty oe
A
pare
at
woe
esau
a
Ante athe ft
aedeeinew
4 ob stin a te
sf
nist CHAPEL oly 4 Het
sata ey ite ry si thy
tht
dati
o
vai he .
bieing
bots gs
i ie
ben
pryees
-
he
ithe
He bay
Wek
Hie
rie
hy ("
.
a rte rer?
ri sicettan nt et ,
t haa
ih iti earth i
' tle
AFlubhe atte Laaite
Pimet aw yiba! urttis
ay
” hye “
cae | iM
oie
setts inyaee ioe
Topic ‘
A
ri
BN) sho
aise sdeden
ieee
Pervny His
y rf le hi hbiine
by tatberaehs aoa ah
irl ae iin wet Ari ed: iis: ict
tt ried nwa iy; Patt hate ‘a each iat saat
mn
1h
‘ Hasta tie he
ahd iets bet
aerate hag
fae ‘sie he
a Wath
ere ti ain
beidiaiay he
mel Siihebea) pea
uve eette: tet \
Thal tied 2
t i 3
vty Ai Eas iihaid
ai Weta hth ata bona
29: Wane oh
ie ae
basis donee
y Ny tae Tryp
ane 5 Mi teri
Si att sha hay) 4
at a
vee Init i
"
ats npr Fett
atte Sen peti :
ae eho bgt TE Hees iele es
Oty sash yy
weratite
Hee ¢ aie
sine es
[Real as
bets ats
iy
nar a3
Het ae ‘|
Acar
“
ahha
iin: i th sib as
ns Bb
iat a
stb Leite
Or haoe
Hie ih yi
that we ert) brat rth
' lanes iaitala
ts i
beth ree mits
Vel toa bot
" wits
bet wre
PUT forte puny Hare
ei baidegiesdts tie
ibe A Yyh HALIM Ya radon) 1 s)d 00) eis
i faa Astpevesevesaesit estates
teh he ih Tt atte yar
Cr
it
if ie A ee
it rhe ht beet
Ch Meee oheat ¥
40 28 aha a NV yh
Hah eh sw
ieee SULA +e ¥ Hey
a ‘iene fiat ' oe
ibaa ie bed it
i\iabas Hy pent teh : pare Pb bet Harb OH Tees 1
+ a sted a (4 ery hi pen Hot Lot i yobesnisnate te ae
ie yee i Bae vai ee Appi } 3 Cie IH r!
vanes He Hinges) (ehh gdh i tne hit uae bawvaihl ty bad) "’
eee nhs ihe 444) Han shee Nits fi Ret of este ea oy janet ae [are nvaey
asaumcnae| 4 hint saith ke 04 a 5 hyalina wales ial tH
i iN f “iy Ht Ad haliy ni i an tubratgeese tiie . he tH fet HH 1}0e9 eed
howe \ felaaitis Sia iht fis : ee sik
mi Hine
heen’
pent
t
ha
bf ate Hh i
Her antes tl
atts Hi adbeds! + aly *
4 nit ste SiN ies veel dyad
ky rei Nhededy ‘ii nial nth
B}) Gad diay Rea ideal va nee
ait sails i r ved * Sj
dubs hide?
aii
ails Haatitentasy vty bt
f i striae Nir pate A} mache ae
214 ‘ sobhitens A>
we *¥ Aine
atipe
' seo raee 4
4A) Tough pan 40N8 ‘ A ih ae Labalren 1 iat 9 ee
hit is beta
Ri
“ aie i eee bo
ath eye ‘ i aaah abkdaps ans iti (4 a atid
Hi ately) a ui \ ; \ 17%
tate > i
54 4 rT rit
th tite AY inet nies Het \ Ae i , write
hat hy Tvandiad 45
und tank 4 séshed ‘ 9 Hilal wane
1 mest vehi the 9 ne hy \ it ‘ (Nat
suk jy
sfipane
y f gab)
VEU tiaete
‘aban ai
tH abt ity
Haha tari
Se
Hai Wii!
sneha
+
att i i ih ft
Ake avi ta aa tase dy Wie bt Ma Fil
Hat); it aan : thy rant
abrde's {
dSdell anges Sei atiie ‘ ae NY any
Met aee hth eH aa) dnev are war BE TetiL YA iyaihy nf is tinse
sbareided TAS IF Pere dedailets tru i ae Hitt ah hie mi 1s
yea Db Tit eit Cree i eathy 4 t iil sae) bauer
sadegy ithe ad :' U ha , af
ft tes ih tind j a 4 eet:
hipaa bay ie ; ‘as
' ss Hsiiees
wean
me ite
i vt ie te Wh eis
i it seein i ial
A man fee ea
qutiage pa ae
ott irveye “4
eetae
areas
These
ht i?
nnd t 7 apa ite tte |
Conny While abpaiedeshauusy a ; bh etal si | r
Laie aa igatehe: ae
\
Hicsdiys
} ios t fila
Ape ATRY ; ( swunnte
neath | My cit! DEreitey bopely adr l al
sroibeahiod tod qtaeiate’ he
Ha ta spitktyei ietet ti gaat igre in 10H Rane C
reerctetl le Tita ied A saienar tel hau
Cy Ee et Le ‘leit iit acreeste Meetiopesteaehte
cat ie af etches ai r ae Ph Rivals
4 : Behe drat abby
ert ia rs i, isa inbhsceyendt it}
mente hPa
|
+imiaad
esti !
i , y ath Meg) ‘
4 * * }
Na ah ae ‘ a0 Hi +4 " i Mite
nt rhe uae . 9 rng n bret
a rates iu if i
Ladin Biting {
Ln,
nye if 0 4
tat a vais fh ie sat 4)
a4 Oe hes t
+ itt \4 beh a by a
aaa Uae dg aie)
ert a4 he
+p
t
at nae drasad Tepes
Hada staan 4 a tae irl v yt
tL day sli Houaae ad “ Ast ai 1 iH
rh iid th t ne tit sabi whMoy airy i ‘ vel mths
A121) let an i oH laters
“: fe Bat dee
eats
Weysh ‘ . ,
tik nee rm stig , rele r (tt Nederasees
Wer tionver si jleeul Buen Melaorise ret
i bitrahst +4) Met tt ‘1 \* 1 ? p saison
dal as ‘ pati ; Ht Het WV mised iim
nt fe oy tit +i ane Ceirenin ul ¥
we
Ube tf te oat
if
Prasanna weedy
are Bante here nh orn
he tt iar 8 a We aM ape ly ‘ pest tuande
(oa) : ; tadsee
4009 ws
¢ 4 t ;
ida sreswiges eH ach irr te th tr io
1: YO fete
try i; ype n . . ‘ whee ha
sitet i ia i i sists) sin rtetiteeg eae le
Vly 4 a ah wre
: isis Weer alat aes
ay Wrens sAL nie Pret
Aehnstenaestaes
Seerttitg a He
¥ i" Hanes vie Est A mah Gala &
44 Hyer f Hh Dn *t ae tha
vie Hpi se) hk
oy ure deine
ao yh
4
i
HN ae 4 H hates
Usenet He
bib poh
Gy Bey At atta e®
Pan) pb rhbt:
Hhigitenengie } ‘ ne 1" ‘ eee
NN HAY bat bengal na th 3194) eivagiied ‘ r wey acN ta dlae dhe
i Sat» 446
i beh ce coy eng ete
inte 4a i php pein tabs deus oq sown a4
bene ak as +} 3.
wid ag’
‘ Wr
Heme Wiha trig) > 7 soi He
withing Siler bianiaye eerste ty ie aber ec ete tars
Pett A aie ph.
Fa sey ae
ete hee rethestte)
‘ gwen ya sar tawie
: > Pat iipbaetnce nee
Be bat 44444 ‘th ue rhe fet G i ays
Cr ‘
wae : : Hie be abtett iuae yy
‘ 4) ah os hed ate ntas i tisdalda ass damasereeaerveoner
Peles ata ath 9" hey ebsites Wirt irty Se ek cal she te
ef enenaele:
ty
allie mr barvenrerer si hy igi ese
tts it ropptt Pai ta toe Ae PUI eh td pcherath
ry ih J f- *
ry Beccary Ret
1
i tee rasa
i a3 tar? eeaaaathe pict
Huth
3 ealavey
hou “en * ant as ge ii br ” L Hert ’
doese very tr : 44 Teaeent ts
Hai pepe ts thea ph wash hy pb why sreutitas
apenas bh
}aete ty
Return this book on or before the
Latest Date stamped below.
University of Illinois Library
L161—H41
UP
Reon any 3,4
LEACH Ray TAR OED
ei Mi
} i ‘ 7 yy 7
y i 7 j W le “ae i
‘ ' : : ek hy } ay
' We j f y uy i VPN ren
li ! Ayeer CSR Feet : } Aa
ra ‘ / ‘ ya Ae
. hn ; i A pete ah ip
9 j Hey east tN, Pee yen i
| ( ; ) x ‘ \ 1 oe ‘
: \ { fi 1 f ‘ ; yt Va
i; . ]
} ‘ ’ }
4,
a”
\
Kf A
anh
iy
Digitized by the Internet Archive
in 2011 with funding from
¥
t
versity of Illinois Urbana-Champaign
. eh aaa a) been
ps F a
bey
ILLINOIS BIOLOGICAL
| MONOGRAPHS
VoLUME XIX
PUBLISHED BY THE UNIVERSITY OF ILLINOIS
URBANA, ILLINOIS
B
Pad f)
j -
L
Ve Ey
CONTENTS OF VOLUME XIX
Nos. 1-2. The Ostracods of Illinois — Their Biology and Taxonomy.
By C. Ctayton Horr.
No. 3. The Genus Conotrachelus Dejean (Coleoptera, Curculionidae)
in the North Central United States. By HERBERT FREDERICK
SCHOOF.
No. 4. The Embryology of Larix. By JAmEes Morton ScuHopr.
ILLINOIS BIOLOGICAL MONOGRAPHS
Vol. XIX Nos. 1-2
PUBLISHED BY THE UNIVERSITY OF ILLINOIS
UNDER THE AUSPICES OF THE GRADUATE SCHOOL
URBANA, ILLINOIS
EDITORIAL COMMITTEE
Joun THEODORE BUCHHOLZ
FRED WILBUR TANNER
HaRLEY JONES VAN CLEAVE
UNIVERSITY
OF ILLINOIS
t: PRESS tr
800—7-42—23751
THE OSTRACODS OF ILLINOIS
Their Biology and Taxonomy
WITH ‘NINE PLATES
BY
C. CLAYTON HoFF
CONTRIBUTION FROM THE DEPARTMENT OF ZOOLOGY
OF THE UNIVERSITY OF ILLINOIS
THE UNIVERSITY OF ILLINOIS PRESS
URBANA
1942
: is
Tt ce ey
iy
a
ACKNOWLEDGMENTS
The writer wishes to express his sincere appreciation to Professor H. J.
_ Van Cleave under whose direction this work was completed. Not only
» did he give valued suggestions and constructive criticisms during the
_ course of the investigation but he also made it possible for the writer to
» examine material in the accumulated research collections of previous
- students, especially S. W. Howe and Samuel Eddy, who have left
_)material in his care.
¢ The writer is also indebted to several persons, including Robert G.
~Yapp, Bertrand A. Wright, and Victor Sprague, for gratuitous collections
containing material relative to the ostracods of Illinois. Dr. David H.
* Thompson, Dr. George W. Bennett, Dr. Donald F. Hansen, and Dr.
”’ Herman B. Chase merit the thanks of the writer for privileges allowed
him during the course of the field work. These persons, all connected
with the Illinois State Natural History Survey, made it possible for the
writer to secure material from otherwise inaccessible areas.
This study was aided by a grant from the American Association for
the Advancement of Science through the Illinois State Academy of
Science.
CONTENTS
Introduction :
Review of the Literature ,
Methods of Collection and Preparation :
Biology of Illinois Ostracods . he:
Habitats.
Physical Racers in 1 the Habitat
Biotic Relationships
Seasonal Distribution
Reproduction and Ontogeny
Food . ?
Geographical Bienibution of Ostracods :
Morphology of Fresh-water Ostracods
Shell
Body Se mentition aed Appendaees :
Respiratory, saad Excretory, Dieestive! and Neaous
Systems an ee oer ae sane
Reproductive costa
Taxonomy 5
Order Ostracoda :
Suborders of the Order Ostracada
Families of the Suborder fasted SPUSEE. Se
Family Cypridae . ;
Subfamily Candoninae s. sir.
Genus Candona Baird 1845. .
Candona punctata Furtos 1933 .
Candona fluviatilis sp. nov. .
Candona simpsont Sharpe 1897
Candona albicans Brady 1864
Candona biangulata sp. nov...
Candona recticauda Sharpe 1897
Candona sharpei sp. nov. :
Candona distincta Furtos 1933 .
Candona crogmaniana Turner 1894
Candona caudata Kaufmann 1900 .
Candona sigmoides Sharpe 1897
Candona indigena sp. nov.
Candona suburbana sp. nov.
Candona fossulensis sp. nov.
Candona acuta sp. nov.
Subfamily Cyclocyprinae Beslan ace
Genus Cyclocypris Brady and Norman 1889 pc eae ON
Cyclocypris forbest Sharpe 1897
Cyclocypris sharpei Furtos 1933
Genus Cypria Zenker 1854
Cypria turneri sp. nov. .
Cypria mediana sp. nov.
ILLINOIS BIOLOGICAL MONOGRAPHS
Cypria obesa Sharpe 1897
Cypria maculata sp. nov. .
Cypria ophthalmica (Jurine 1820) Brady. eal
Norman 1889...
Genus Physocypria Vavra 1897 . f
Physocypria pustulosa (Sharpe 1897) S W. Miiller 1912
Physocypria dentifera (Sharpe 1897) G. W. Miiller 1912
Subfamily Ilyocyprinae aoe: ane
Genus Ilyocypris Brady and Nicer 1889 ;
Ilyocypris gibba (Ramdohr re cies endl
Norman 1889 _. 2e ene
Ilyocypris bradyi Sars 1890 .
Subfamily Cyprinae s. sir.
Genus Cypricercus Sars 1895.
Cypricercus tuberculatus (Sharpe 1908) comb. nov.
Cypricercus fuscatus (Jurine 1820) Sars 1928 :
Cypricercus reticulatus (Zaddach 1844) Sars 1928
Genus Cyprinotus Bradwaleoo aie me
Cyprinotus incongruens (Ramdohr 1808) Tinaas? 1895
Cyprinotus pellucidus Sharpe 1897 Ba:
Subfamily Notodrominae . :
Genus Notodromas Lilljeborg 1853 .
Notodromas monacha (O. F. Miller 1776) Lilljeborg 1 1853
Genus Cyprois Zenker 1854... :
Cyprois marginata (Strauss 1821) Z Derizst 1854
Subfamily Cypridopsinae :
Genus Cypridopsis Brady 1867 ._.
Cypridopsis vidua (O. F. Miiller 1776) Euado 1867 . :
Genus Potamocypris Brady 1870 .
Potamocypris smaragdina (Vavra 1891) Daday 1 1900
Family Darwinulidae. . : :
Genus Darwinula Brady antl Norman 1889 :
Darwinula stevensoni (Brady and Robertson 1870) Brady
and Norman 1889 ; :
Family Cytheridae :
Subfamily Limnocytherinae . .
Genus Limnocythere Brady 1867
Limnocythere verrucosa sp. nov.
Limnocythere reticulata Sharpe 1897
Limnocythere illinoisensis Sharpe 1897
Subfamily Entocytherinae
Summary
Bibliography
Plates
Index
INTRODUCTION
The recent fresh-water ostracods of Illinois, or for that matter of North
America, have received relatively little attention from either taxonomists
or ecologists. One of the most obvious explanations for the neglect of
study of the American fresh-water ostracods undoubtedly has been their
relative absence from most open-water plankton samples. Thus they have
been delegated little attention from various American investigators who
have made detailed studies of other crustaceans such as copepods and
cladocerans which are important as plankters in fresh waters. The group
has also been overlooked by investigators working on the bottom faunas
of American lakes and rivers because the ostracods, being small and
active, readily escape from the usual bottom sampling apparatus. Even
those investigators concerning themselves with aquatic vegetation and
associated animals have often neglected the ostracods, largely perhaps
because they were unable to make specific determinations for themselves,
and there have been few American authorities to whom material might
be submitted for identification. For anyone but the specialist, the specific
determination of many of the species has been and still is almost impos-
sible, or at least impractical because the literature is scattered and there
are many dissensions in classification and nomenclature. Moreover, it
takes considerable time to learn to locate the structures on which specific
determination often rests. For these reasons, it is impractical for anyone
not especially interested in the taxonomy of ostracods to identify any
except the easily recognized species, or species from areas in which a
fairly complete survey of the ostracod fauna has been made. The only
areas in North America in which fresh-water ostracods have received
more than minor consideration are Ohio, Illinois, Massachusetts, Florida,
and Washington.
Apparently few investigators have cared to give their attention to an
intensive study of ostracods. One reason for this undoubtedly is the
difficulty of working in the group. As specific determination usually
depends on minute details of the appendages isolated by careful and
tedious manipulation, few American investigators have given prolonged
attention to the group. Besides the mechanical difficulties encountered,
there is a decided deficiency of literature in English, the papers that are
available being old or unsuited to open the way readily to anyone desiring
to begin work on these forms. Nearly all the more important papers are
written in German, and since most of the genera and many of the species
are not confined to any one continent, little can be done in the way of
taxonomy without consulting these foreign publications.
The stigma of apparent lack of economic or biologic importance has
perhaps led many investigators to ignore the ostracods. In contrast to
10 ILLINOIS BIOLOGICAL MONOGRAPHS
what is generally thought, however, the ostracods do play an important
role in the economy of fresh waters. As most species feed on diatoms,
bacteria, and minute particles of organic material in the water and are in
turn food for many of the larger animals, chiefly fish, they certainly are
of some economic significance. Very often, no doubt, a lack of emphasis
on ostracods as food for fishes has been the result of an inability to
determine taxonomically the species found. In practically all surveys
concerned with the availability of food for fishes, the ostracods are
identified only to genus, and in some publications all are listed under the
blanket term ‘“‘Cypridae.”’ While it has been well known since the time
of Forbes (1888) that many Illinois fishes consume ostracods as a part
of their food, the extent to which fish sometimes ingest ostracods is not
generally realized. One individual instance of the large numbers of these
animals occasionally consumed by fish is shown in an examination of the
digestive tract of a single adult individual of Catostomus commersonu
(Lacépéde) from the strip-mine area near Oakwood, Illinois. The ostra-
cods, which completely packed the digestive tract to the exclusion of
almost all other kinds of food, included no less than six species, three of
which predominated in numbers.
Not only may ostracods be considered economically as potential links
in food chains but they are also of interest because often they serve as
intermediate hosts for some of the Acanthocephala, especially those which
parasitize fish. As an example of an Acanthocephalan life cycle in which
an ostracod is the intermediate host is the life cycle of Neoechinorhynchus
cylindratus (Van Cleave 1913) as worked out by Ward (1940). N. cylin-
dratus as an adult parasitizes the large-mouth black bass and has as the
first intermediate host Physocypria globula Furtos 1933 (=P. pustulosa
(Sharpe 1897) G. W. Miller 1912). In examining thousands of ostracods
mounted on slides, the present writer has found several species infected
with Acanthocephala. In material from permanent lakes and streams, the
percentage of infection may run from one to one and one-half per cent.
While this incidence of infection is not high, it shows the possibilities of
securing material for working out life histories in the Acanthocephala.
Since many of the primary and secondary intermediate hosts of Acantho-
cephala are fishes, all stages of the parasite are readily available, and
infection experiments may be conducted without great difficulty.
Besides being of distinct economic importance, the ostracods are bio-
logically interesting. Concerning the ostracods in American fresh waters,
little is known of the habitats, the factors which govern distribution, or
the ecological associations of which they may play an integral part. The
present writer has attempted to bring together field data regarding the
habitat relationships of the ostracod species of Illinois. The variability
shown by various species of ostracods also merits detailed inquiry, The
OSTRACODS OF ILLINOIS—HOFF 11
most noticeable variations are in color, size, and shape of shell and the num-
ber and degree of development of tubercles along the shell margin. There is
some indication from the field data that the shell color in some species,
as Cypridopsis vidua, may be correlated with the season and the amount
of algae available in the water. Whether or not an abundance of green
plant material used as food causes a deepening of the shell color must be
determined experimentally. The possible development of races in various
local areas is a problem of academic significance. Certain available
records of discontinuous variations, such as the number of tubercles along
the shell margin in Physocypria pustulosa, lend themselves to numerical
consideration. Consequently, they may be conveniently used in detecting
the presence of isolated races differing from each other in the number of
tubercles. Such studies may lead in time to the final settlement of the
status of certain questionable species based on differences which are pos-
sibly only expressions of individual variation and which appear to the
writer to be of less than subspecific importance.
The writer, recognizing the difficulties involved in the identification
of ostracods and the lack of knowledge regarding their biology, has
attempted herein to make a contribution of such a nature that ecologists,
‘fresh-water biologists, and zoologists in general may have available a
workable treatise by which they can, in the first place, identify species
occurring in Illinois and, in the second place, gain some insight into the
biology of the species found in the state. Paleontologists, who are now
giving much attention to the study of fossil forms, may find the informa-
tion given herein useful in the interpretation of fossil faunas of fresh-
water ostracods. It is hoped that the order Ostracoda may continue to
be the subject of additional investigation, since direct and detailed infor-
mation regarding the life histories of most Illinois species is extremely
meager, data on the distribution of many species in some parts of the state
are entirely wanting, and few physiological and experimental studies have
been reported in the literature.
REVIEW OF THE, LITERATURE
History of Basic European Work on Ostracods.—The ostracods of
North America are little known in comparison with the relative complete-
ness of the knowledge of European forms. Since American workers have
followed closely the schemes provided by European writers, a survey of
classical European works is considered essential to a study of ostracods
indigenous to America. Several comprehensive works have been published
on the ostracods of European countries, and complete faunal lists have
been very accurately compiled. A comparison of the literature relative to
American forms and that concerning European species shows distinctly
12 ILLINOIS BIOLOGICAL MONOGRAPHS
that the knowledge of ostracods in America is thirty or forty years behind
that in Europe.
The first important publication on ostracods was that of O. F. Miiller,
in 1785, entitled “Entomostraca seu Insecta testacea, quae in aquis Daniae
et Norvegiae reperit, descripsit et iconibus illustravit.’”’ Between the
beginning and middle of the nineteenth century, several important Eu-
ropean papers appeared. These included a work by Jurine in 1820 on
the ostracods in the vicinity of Geneva; a doctor’s dissertation by
Zaddach in 1844 concerning the ostracod. fauna of Prussia; and Lillje-
borg’s publication in 1853 on the ostracod species of Scandinavia. These
studies were largely taxonomic in scope. In 1854, Zenker published his
“Monographie der Ostracoden,’ a publication of eighty-seven pages
which included not only a taxonomic but also a biologic consideration
of the known ostracods. The first important publication in English was
written by Brady, appearing in 1868 under the title ““A Monograph of the
Recent British Ostracoda.” With Norman in 1889, Brady published
“A Monograph of the Marine and Freshwater Ostracoda of the North
Atlantic and of North-Western Europe. Section J. Podocopa.” Two
years later, Vavra (1891) monographed the ostracods of Bohemia. In
1900, two very important comprehensive papers were published, one by
Kaufmann (1900a) on the “Cypriden und Darwinuliden der Schweiz” and
the other by G. W. Miller under the title “Deutschlands Stisswasser-
Ostracoden.” Early in the present century, G. W. Miller (1912) brought
out his summarizing volume on ostracods as a part of the series “Das
Tierreich.” Up to the present time, this has remained the only authentic
and comprehensive world-wide monograph on the ostracods, and it is still
the basic publication for anyone beginning taxonomic work in the group.
Among recent monographs of the ostracods of European countries have
been those of Alm (1916) on the fresh-water ostracods of Sweden and
of Sars (1928) on the ostracods of Norway. More recently Wagler
(1937) has published a comprehensive work on European ostracods in
his volume on Crustacea in the series entitled “Die Tierwelt Mittel-
europas,’ and Klie (1938a) has published a monograph on German
ostracods in the series “Die Tierwelt Deutschlands und der angrenzenden
Meeresteile.”” While these major publications have been appearing from
time to time, there has been an influx into the periodical literature of
smaller papers concerned with the taxonomy, morphology, or ecology of
a small group of ostracods or the ostracods of a local area.
Comprehensive works on the biology of the ostracods are not so
plentiful as those concerned primarily with taxonomy. In many of the
taxonomic papers, however, some reference is made to the general biology
of the species under consideration. For instance, Zenker’s monograph in
1854 included much data of a biological nature as a background for the
OSTRACODS OF ILLINOIS—HOFF 13
taxonomic portion of the publication. Wohlgemuth (1914) and Alm
(1916) were among the first to write in detail on the biology of the
ostracods of a definite region, Wohlgemuth working on the ostracods of
Saxony and Bohemia and Alm on those of Sweden. While G. W. Miiller
(1927) wrote a general account of ostracods in the Kukenthal-Krumbach
“Handbuch der Zoologie,” the most complete account of the biology as
well as the anatomy and development of fresh-water ostracods is the
account by Klie (1926a) in the series “Biologie der Tiere Deutschlands.”
This publication is applicable to forms from the United States as well as
German species, because many of the species from the two countries are
identical or closely related.
History of the Study of American Ostracods.—Compared with the
attention which has been given ostracods by European writers, the meager
work by Americans has consisted chiefly of small, scattered papers. With
the exception of Klugh’s (1927) work on the ecology of a few Canadian
species, these papers are chiefly only of taxonomic or zodgeographical
importance. The earliest publication on the ostracods of North America
is the description by Haldeman (1841) of two new species of “Cypris”
from Pennsylvania. The same author (1842a, 1842b) gave descriptions of
two more new “Cypris” from Pennsylvania and one from Massachusetts.
These ostracods were so inadequately described that their real identity is
unknown, and they are listed among the dubious species by G. W. Miiller
(1912). The best known of early American workers in the field of ostra-
cods are Herrick, Turner, and Sharpe. Herrick published several papers,
of which his early ones (1879, 1882) refer in part to the ostracods of
Minnesota. In these papers he described a few new species, but in some
instances so incompletely that it is impossible now to recognize them.
The early deficiency of knowledge of American ostracods is shown by
Underwood’s publication (1886) of a list of all the described ostracods
from America north of Mexico. Here are listed fifteen species, many of
which are now considered dubious; none of them were from Illinois. In
1887, Herrick published a list of the fresh-water and marine crustacea
of Alabama. This included ten species of ostracods, of which five were
described as new. Turner began publishing on ostracods in 1892 and
after the appearance of several small publications (1892, 1893, 1894)
concerning new species and records, he published in 1895 a work on the
“Fresh-water Ostracoda of the United States,” which appeared as part
three of the “Second Report of the State Zoologist of Minnesota.” This
publication continued to be the most complete of any on American
ostracods until the appearance in 1918 of Sharpe’s account in Ward and
Whipple’s “Fresh-water Biology.” Besides Herrick’s and Turner’s works,
a few new species were described by Chambers oo ) and by Forbes
(1893). from the western United States.
14 ILLINOIS BIOLOGICAL MONOGRAPHS
Shortly after the appearance of Turner’s account of the “Fresh-
water Ostracoda of the United States,’ Sharpe (1897) published an
account of the ostracods of Illinois which, for his time, excelled in
completeness all other state lists. His work was based on a large number
of field collections. Sharpe followed this early work by a series of pub-
lications (1903, 1908,.1910) based on material collected by himself in
Illinois and material from other localities deposited in the United States
National Museum. His last publication (1918) was a complete and
concise summary of all knowledge of American ostracods up to the time
of publication.
Between 1900 and 1933, no monographic studies except that of
Sharpe (1918) in Ward and Whipple’s ‘“Fresh-water Biology” appeared
on American ostracods. Several American workers, however, published
short papers. These papers include reports of a few species in Michigan
and Nevada by Pearse (1910, 1914) ; lists from Rhode Island by Williams
(1907) and from New Jersey by Fowler (1912); two publications on
the ostracods of Massachusetts by Cushman (1905, 1907) ; and reports of
the ostracods from western United States, chiefly Colorado, by Dodds
(1908), Cockerell (1912), Blake (1931), and Brues (1932). A notable
publication was that of Marshall (1903), in which was described the first
Entocythere found on the gills of crayfish. During this period from 1900
to 1933, several European workers also studied material from North
America. Alm (1914) published an account of the Arctic ostracods of
Greenland and part of Canada. Sars, in 1926, gave an account of Canadian
ostracods, chiefly from southeastern Canada. Klie (193la) published an
article which included three new species of ostracods from Indiana. In
1914, Weckel compiled a list of all the “free-swimming” ostracods of
North America, with keys for their identification.
A new era has begun in the last decade with the publication by Furtos
in 1933 of a complete survey of the ostracod fauna of Ohio. She fol-
lowed this in 1935 by an article on the fresh-water ostracods of Massa-
chusetts and in 1936 by two articles, one (1936a) on ostracods of Florida
and North Carolina and another (1936b) on the ostracods from the
cenotes of Yucatan and vicinity. More recently, Dobbin (1941) has pub-
lished a comprehensive survey of the ostracods of the northwest coast
region of the United States. At the present time, there are few investi-
gators working on ostracods in the United States, and the field is open
for taxonomic and ecological studies, especially those of state-wide
significance.
Reports on the Ostracod Fauna of Iilinois.—Sharpe published the first
work on the ostracods of Illinois in 1897. In this publication, Sharpe
listed twenty-two species, twelve of which were thought by him to be
undescribed. With the exception of two of the reported twenty-two
- OSTRACODS OF ILLINOIS—HOFF 15
species, all of them were from Illinois, chiefly from the vicinity of
Havana, Mason County, Illinois where the Biological Station of the
University of Illinois was located. A few of the twenty species in this
initial publication are considered synonyms by the present writer, but
seventeen of them are retained as valid. The writer has failed, however,
to rediscover five of those listed by Sharpe in this early work.
Sharpe followed his first paper by three others, all of which have
some reference to Illinois ostracods. Sharpe’s works of 1903 and of 1910
reported little except a few additional references as far as Illinois is con-
cerned, but his publication of 1908 contains the first records of five addi-
tional species from Illinois, one of them previously undescribed. Three
of these five have not been rediscovered by the present writer. Only three
other publications are available with reference to the ostracod fauna of
Illinois. One of these is the reference by Kofoid (1908) to several species
in the Illinois River at Havana, Illinois. The second is the mention of five
species from the Chicago area by Shelford (1913). Neither of these
reports contain important new records for the state, but they merit men-
tion here as two of the few instances where ostracods found during the
course of an extensive ecological investigation were carefully determined
to species. Identification in both of these papers was by Sharpe. The
third paper is a publication by the present writer (1942) in which are
described two new species of Entocythere epizoic on crayfishes from
Illinois.
Since the time of Sharpe, no one has published the results of any studies
on the free-living ostracods of Illinois. The present writer has, by a study
of 713 field collections from sixty-six counties, raised the total of reported
free-living species from Illinois to thirty-nine. Of these, thirty-one have
been seen by the present writer, while eight were reported by Sharpe but
not found during the course of the present investigation. This lack of
rediscovery is perhaps the result of two factors: (a) a scarcity resulting
from the localized or limited seasonal occurrence of certain species (this
is undoubtedly the case with Cyprois marginata, which was reported by
both Sharpe (1908) and Shelford (1913) from a pond in Jackson Park,
Chicago) ; and (b) an erroneous or incomplete description or one based
on abnormal individuals, which has made redetermination impossible.
Many of the species not found by the present writer in his collections
will certainly be rediscovered when additional collections have been made,
since some species are rarely observed, as, for instance, Darwinula steven-
soni and Notodromas monacha, each of which is represented in the present
writer’s collections by a single individual.
The thirty-nine free-living species reported herein as occurring in
Illinois include eleven species described as new to the literature. Seven-
teen of the thirty-nine species are new records for IlIlinois.
16 ILLINOIS BIOLOGICAL MONOGRAPHS
The following list is a summary of all records concerning free-living
ostracods in Illinois.* In previous reports, species have been recorded
often under names which have required some change to bring the
nomenclature up to date. For the names used by earlier writers in report-
ing ostracods from Illinois, the reader is referred to the synonymy under
the taxonomic discussion of each species. Here the writers reporting
Illinois records are indicated by numbers in parenthesis after the name of
each species, as follows: (1) Sharpe 1897; (2) Sharpe 1903; (3) Sharpe
1908; (4) Kofoid 1908; (5) Sharpe 1910; (6) Shelford 1913; (7) the
present writer.
Suborder Podocopa s. str.
Family Cypridae
Subfamily Candoninae s. str.
Genus Candona Baird 1845
C. simpsoni Sharpe 1897 (1, 4, 7)
. punctata Furtos 1933 (7)
. fluviatilis sp. nov. (7)
. albicans Brady 1864 (7)
. biangulata sp. nov. (1, 7)
crogmaniana Turner 1894 (7)
. sigmoides Sharpe 1897 (1, 4, 7)
recticauda Sharpe 1897 (1)
sharpet sp. nov. (1)
caudata Kaufmann 1900 (7)
distincta Furtos 1933 (7)
. indigena sp. nov. (7)
. suburbana sp. nov. (7)
. acuta sp. nov. (7)
. fossulensis sp. nov. (7)
Subfamily Cyclocyprinae
Genus Cyclocypris Brady and Norman 1889
C. forbesi Sharpe 1897 (1, 7)
C. sharpet Furtos 1933 (3)
Genus Cypria Zenker 1854
C. turneri sp. nov. (1, 4, 6, 7)
C. mediana sp. nov. (7)
C. obesa Sharpe 1897 (1, 5, 7)
C. maculata sp. nov. (1, 4, 7)
C. ophthalmica (Jurine 1820) Brady and Norman 1889 (7)
Genus Physocypria Vavra 1897
P. pustulosa (Sharpe 1897) G. W. Miller 1912 (1, 4, 7)
P. dentifera (Sharpe 1897) G. W. Miller 1912 (3)
Subfamily Ilyocyprinae
Genus Ilyocypris Brady and Norman 1889
I. gibba (Ramdohr 1808) Brady and Norman 1889 (7)
I. bradyi Sars 1890 (7)
Subfamily Cyprinae s. str.
Genus Cypricercus Sars 1895
C. tuberculatus (Sharpe 1908) comb. nov. (3, 7)
*Two additional species of ostracods, Entocythere illinoisensis Hoff 1942 and E. copiosa
Hoff 1942, have been reported as living in the gill chambers of crayfishes in Illinois (Hoff, 1942).
Since these species are epizoic, they are excluded from this list.
DVAYVAAQ AD AQAA AAAN
OSTRACODS OF ILLINOIS—HOFF 17
C. fuscatus (Jurine 1820) Sars 1928 (1, 3, 6)
C. reticulatus (Zaddach 1844) Sars 1928 (1, 3, 6, 7)
Genus Cyprinotus Brady 1885
C. incongruens (Ramdohr 1808) Turner 1895 (1?) (7)
C. pellucidus Sharpe 1897 (1, 2)
Subfamily Notodrominae
Genus Notodromas Lilljeborg 1853
N. monacha (O. F. Miller 1776) Lilljeborg 1853 (3, 6, 7)
Genus Cyprois Zenker 1854
C. marginata (Strauss 1821) Zenker 1854 (3, 6)
Subfamily Cypridopsinae
Genus Cypridopsis Brady 1867
C. vidua (O. F. Miller 1776) Brady 1867 (1, 4, 6, 7)
Genus Potamocypris Brady 1870 °
P. smaragdina (Vavra 1891) Daday 1900 (1, 7)
Family Darwinulidae
Genus Darwinula Brady and Norman 1889
D. stevensoni (Brady and Robertson 1870) Brady and Norman 1889 (7)
Family Cytheridae
Subfamily Limnocytherinae
Genus Limnocythere Brady 1867
L. reticulata Sharpe 1897 (1, 7)
L. illinoisensis Sharpe 1897 (1, 4)
L. verrucosa sp. nov. (7)
METHODS OF: COLLECTION. AND’ PREPARATION
The material on which this publication is based was collected by the
writer during the vernal, aestival, and serotinal seasons of 1940. The
collections were made in sixty-six counties of Illinois. An attempt was
made to collect impartially. During most of the collecting trips, all avail-
able waters were examined, even though the habitat appeared unfavorable
for ostracods. In spite of the examination of such uninviting waters,
about two-thirds of the samples collected contained one or more species
of ostracods. In all, 713 samples from Illinois actually containing ostra-
cods formed the basis for this investigation.
Almost without exception, collections were made with a Birge cone
net eleven inches long and four inches in diameter at the open end.
The open end is fitted on a sheet-metal cylinder which is closed with a
cone of coarse brass wire netting of about three-eighths inch mesh. This
cylinder keeps the open end of the net from collapsing and the wire
netting prohibits the net from collecting an assortment of vegetation and
debris. The organisms are caught in a half-ounce bottle attached to the
apex of the net. The entire net with the metal cylinder at the larger end
and the collecting bottle at the apex is mounted on a toboggan made of
galvanized sheet metal, the cylinder being firmly attached to the sled at
the forward end. The collecting bottle lies on the sheet-metal sled and
1S ILLINOIS BIOLOGICAL MONOGRAPHS
when in use is held in place by rubber bands fastened through two small
holes in the bottom of the sled. This holds the net approximate to the
sled at all times and keeps it stretched out in a cone. The adaptation of
this apparatus was suggested by the description of the plankton trawl
described by Galtsoff (1937). It was found that this net could be dragged
on the bottom or through vegetation and roots as well as against rocks
without fouling or injury to the net. Samples were made from all kinds of
habitats and often several samples were taken from the same general
locality in order to include the several available habitats and detect, if
possible, any habitat relationships. Each time after using, the net as well
as the bottle was washed with as clear water as was obtainable, and from
the nature of the samples it is obvious that such washing, even though in
the same water from which samples were taken, was effective and indi-
viduals were not carried over in the net to contaminate the next sample.
In instances where clear open water was not available for washing the net,
it was well rinsed just before using in water from which the next collec-
tion was to be made.
While quantitative methods are generally recognized as desirable in
taking plankton samples, the habitats in which ostracods are to be found
preclude the possibility of adapting quantitative methods in the sampling
carried on in the present investigation. The cone net is the only apparatus
by means of which adequate samples of water could be strained from
weedy ponds, algal mats, and the water immediately over mud bottoms
where ostracods are abundant. Perhaps following the same historical
development as that through which plankton studies in general have gone,
the strictly qualitative methods essential in the present survey may be
supplemented at a later date by quantitative methods for given habitats
or for limited groups of species. At least for the present the writer felt
that the infrequence of occurrence of some species in the numerous
qualitative samples gives justification for relying on relatively numerous
qualitative samples for the initial faunal survey.
At the same time as the samples were taken, a record was made of
the date, location, and certain physical factors as the kind of habitat, the
force of the current, if any, the nature of the bottom, and the turbidity
of the water. In some instances, the hydrogen ion concentration was
determined with a LeMotte comparator, using bromthymol blue as an
indicator. On making each collection, the associated vegetation was noted
in considerable detail in order to learn whether or not there might be a
correlation between the presence of certain species of ostracods and the
kind of vegetation present. These data were entered in a permanently
bound field notebook under a collection number and the date. In the jar
containing the sample, there was placed a paper on which was written the
date and number of the collection. After examination in the laboratory, all
OSTRACODS OF ILLINOIS—HOFF 19
the collections containing ostracods were given serial numbers and the
field data were transferred to notebooks listing each collection by its
serial number.
After making the collections by running the net through the vegeta-
tion, along the bottom, or on the surface, as the case might be, the sample
was poured from the collecting bottle on the net to a four-ounce oint-
ment jar. Collections were usually allowed to accumulate until noon and
night, when they were preserved by the addition of 95% ethyl alcohol in
an amount equal to the volume of the sample. When the temperature was
very high, it was found necessary to preserve the samples more often than
twice a day because of the biolytic action of the temperature on some of
the organisms. The killing of the ostracods by the addition of an equal
volume of 95% ethyl alcohol to the sample is to be recommended. If
formalin is added or the animals are dropped into an alcohol of high
concentration, many of the animals close the shell tightly, and it is then
difficult to remove the valves for examination of the appendages. When
killed by adding the alcohol as explained above, the individuals in most
species are killed with the shell gaping. If the samples are to be kept for
some time before the ostracods are separated from the other material, it is
well to raise the concentration of the alcohol to about 85% by pouring
off the supernatant alcohol and refilling the jar with a sufficient amount of
95% alcohol. Formalin may be used as a preservative, but the appendages
become stiffened and dissection is made more difficult. Care must also be
taken in the use of commercial formalin, since much of the commercial
solution is not acid-free, and the samples will gradually deteriorate
through decalcification of the shells.
After sorting out the material in the collections, representatives of the
species in each sample were usually mounted permanently for study. This
was necessary for the checking of the identification of many of the species,
although it did involve considerable labor and materials. Even though a
few common species such as Cypridopsis vidua and Potamocypris smarag-
dina are recognizable under the binocular dissecting microscope, the
writer made a series of slides of such common forms in order to verify
the identification and discover, if possible, whether or not races occur in
different localities. While it may seem a waste of energy to mount
hundreds of individuals of common and easily recognized species, it is the
only way in which limits of the variation of a species can be determined.
By knowing the limits of variation, one may avoid describing as new the
ultimate ends of a series representing a single species.
Two methods were used in making slides. It was found that glycerine
mounts were convenient and these were used in some instances. A slide
is ringed with several layers of gold size or asphaltum and the ostracod,
after being cleared in glycerine, is dissected in a drop of glycerine on the
20 ILLINOIS BIOLOGICAL MONOGRAPHS
slide within the ring. A cover slip is then placed over the dissection and
sealed with material similar to that used in making the initial ring. While
this is a rapid way of making slides and shows the finer structural details
to good advantage, it has several disadvantages. Among these might be
mentioned the poor preservation of material and lack of permanency in
contrast to mounting media such as diaphane or balsam; the lack of any
staining to bring out certain structures; and the impossibility of mounting
most shells in this way because of their size. This last makes necessary a
separate mounting of shells in some other medium under a second cover
to the side of the glycerine mount. Since the mounting of the shell is
necessary to keep shell and soft parts together and avoid loss of the
former, and since in this method of mounting, the shell has to be dehy-
drated for mounting in balsam or diaphane, it is just as convenient to
dehydrate the entire animal and mount in some one of the more nearly
permanent media.
The most satisfactory mounts of ostracods are made by staining with
acid fuchsin. The ostracods are removed from the preserving alcohol and
placed in a LeFevre embryological watch glass in which they are run
through lessening concentrations of alcohol to water. They are then
washed in a small amount of 1/50-N solution of hydrochloric acid for
about one minute. After pipetting off the acid water, a 0.5% aqueous
solution of acid fuchsin is placed in the watch glass and the animals are
allowed to remain in this stain from one to five hours depending on the
species and perhaps, to a larger degree, on the recency of molting, since
newly molted ostracods seem to stain more favorably than the exuviae or
animals long molted. After staining, the acid fuchsin solution is removed
with a pipette and the material washed rapidly several times in a 1/50-N
solution of hydrochloric acid. The hydrochloric acid solution appears to
intensify the stain. Overstaining seldom occurs, but destaining, if neces-
sary, may be carried out by washing the material in alkaline tap water or
slightly alkalinized alcohol. The material, after washing in acid water, is
run through the alcohol series to absolute alcohol. Since the alcohol is
pipetted off after each treatment and the watch glass retains a small
amount of the solution, it is well to wash at least twice with alcohols of
each grade, especially of the higher concentrations. If mounting is to be
done in balsam, the material dehydrated in alcohol is cleared in xylol (at
least three changes). The cleared animal is placed in a drop of balsam on
a slide under the binocular and the shell removed by the use of fine
needles. The shell halves are removed to a second drop of balsam on
the same slide and covered by a slip supported by bits of broken glass or
pieces of capillary tubing of the appropriate diameter. The appendages
are then isolated in the first drop of balsam and a cover slip added
without any support, since it is necessary to have a thin mount in which
OSTRACODS OF ILLINOIS—HOFF 21
the appendages are extended as much as possible in one plane. By leav-
ing the cover unsupported, it is possible to use an oil immersion lens for
the observation of fine setae and serrations. As the shells and soft parts
take up but little room on the slide, it is often possible to use circular
cover slips only one-fourth of an inch in diameter. If more than one
animal is mounted under a single slip, it may be necessary to employ
larger covers.
A more successful mounting method has been the bringing of stained
material into diaphane directly from absolute alcohol. The principal
advantage of this procedure is the elimination of one of the steps, that
of clearing, thus saving time and materials and avoiding the hardening
action of the clearing fluid. The dissection of material which has not
passed through any of the usual clearing fluids is more easily accom-
plished than it is in material cleared in such fluids. The diaphane clears
the material sufficiently for good observation, a partial clearing really
being much more adequate than clearing in xylol or some other clearing
reagent in which the animals become so transparent that some of the
finer structures cannot be clearly observed. In mounting in diaphane from
absolute alcohol, care must be taken to use several changes of the alcohol
in order to completely dehydrate the material. To avoid the passing of
alcohol into the diaphane, the material should be placed on the end of a
slide in as small a drop of alcohol as possible and the alcohol removed by
absorption with a small piece of filter paper. The animal is then trans-
ferred to the diaphane with a needle. Dissection may be carried out just
as in balsam-mounted ostracods, and the valves, if large, are mounted
under a separate cover. Sometimes it is advantageous to keep the soft
parts intact after removal from the shell in order to be able to orient
properly the various parts of the animal.
-
BIOLOGY OF ILLINOIS OSTRACODS
HABITATS
If sufficient search is made, there will be found scarcely a single kind
of aquatic habitat in which ostracods are not found. Since the state of
Illinois is entirely an inland state, no mention need be made here to the
biology of the ostracods living in brackish or marine waters.
The habitats investigated by the present writer include many kinds
of still and running waters. These have been grouped for convenience
into four types: (1) temporary still waters, including all vernal or
temporary ponds whether old ox-bows, prairie and forest pools, roadside
ditches, or small water-filled depressions; (2) permanent ‘still waters,
including lakes both artificial and natural, swamps which do not dry up
22 ILLINOIS BIOLOGICAL MONOGRAPHS
during the aestival or serotinal seasons, and the lake-like backwaters of
large rivers; (3) temporary running waters and the pools left in stream
beds after the stream has ceased to flow; and (4) permanent streams of
all sizes. Each one of these habitats presents a variety of ostracod species,
but the running waters have fewer species than the still waters. The
only habitat investigated by the writer in which large numbers of several
species did not occur were the waters extremely high in organic material
such as some of the cypress swamps in southern Illinois.
Certain habitats have not been investigated because of lack of time and
facilities. No attempt was made to explore the ostracod fauna of Lake
Michigan, since the lake presents certain problems which make it some-
what separate from the remainder of the state as far as the collector is
concerned. It was also impossible to visit tamarack bogs in the northern
part of the state since these have been closed to the public. A habitat
which will no doubt prove fruitful when investigated is that of under-
ground waters. A large number of species, chiefly of the genus Candona,
have been described from wells, springs, and cave waters in Europe by
Kiefer and Klie (1927), Klie (1934, 1936, etc.), and others. That possi-
bilities are present in Illinois for a study of subterranean species is shown
by the report of Klie (193la) of some species from the waters in an
Indiana cave. The water of crayfish burrows also merits examination.
Creaser (1931) reported Cypria exsculpta (? = Cypria turneri sp. nov.)
abundant in the burrows of the crayfish Cambarus diogenes in Missouri,
and the present writer has taken a few species of ostracods from a
similar habitat in Illinois.
After a detailed survey of the various species of ostracods, it was
found that certain species could be classified as occurring in temporary or
permanent and still or running waters. The minor subdivisions of the
four types of habitat already suggested have no significance as far as the
biology of the ostracods is concerned; and, indeed, the kinds of associa-
tions in a given habitat seem to limit but little the distribution of par-
ticular species. Thus the same species may be found along the margin
of a large lake regardless of whether the sample is taken in masses of
algae, decaying grass, different species of aquatic spermatophytes, or even
from bottom practically devoid of vegetation. In the same manner, the
species found in a small stream usually vary little whether taken from
masses of algae or in mats of plants or whether the collection is made in a
quiet pool or in an area where the water is flowing. The sum total of the
factors which are found expressed in the four types of habitats listed
appears to determine to a large degree, and with few exceptions, the
species of ostracods present. Thus the independent factors such as type
of bottom, current, and associated vegetation determine only to a minor
degree the distribution of most species.
OSTRACODS OF ILLINOIS—HOFF 23
TABLE 1
Table showing the incidence, expressed in percentages, of each species observed by the
writer in temporary and permanent, still and running waters. The name of each species
is followed by the number of collections in which it occurred.
Still waters Running waters
Species Collec-
tions
Temp. | Perm. | Temp. | Perm.
NEPIAONTOISULNCIA 2. 2. oo ce ew 3 100
WANAONE INALZENG. .. 2s. ee ee es 4 100
Candona suburbana..............-.- 2 100
IMAOND JOSSUIENSIS 2 0. ee ce 2 100 a
Cypria ophthalmtica...............4.. 9 44 56
Cypricercus reticulatus............... 31 87 Ke 13
Bandana OLENEUIGIA. 2... c ec e eee 4 50 50
ROU ORUMTIOUCONS oo. s veg esp ee 4 25 of aS ae
DE Se 29 48 38 7 7
GAMMOME SUMPSONE. 225.0 .at see ces 83 39 26 23 12
PNPM REE Ne. os a sa 9 33 45 11 11
DrIMOPSS HAUG. 5... ee 505 20 48 10 DD
Limnocythere reticulata............... 69 16 2 54 28
Cyprinotus incongruens............4-. 16 13 6 44 37
MY DIAMINE CULO Fe oe iv ees te 43 12 42 9 37
Physocypria pustulosa............... 175 8 78 4 10
Potamocypris smaragdina.............| 118 6 41 11 42
MEVGGYDYESIOLODE J. yc ec ct te 44 4 2 49 45
WIBENDTESIDYAA YD... ee 71 1 4 47 48
Limnocythere verrucosd............-.- 4 100 on
Darwinula stevensont.............-.- 1 100
Notodromas monacha................ 1 100
Cypricercus tuberculatus.............. 3 100
ENGIOGYDNIS fOr DESY 2. Sess ees 1 100
Candona crogmaniana..............-- 2 100
MON PIL MINCOLONG ye oe ose 5 50's vs eo 3 33 67 ae
CITE, GALT One eee 3 33 33 33
COUC PT DG 1 a a 1 i= 100 ae
Candona fluvainlis... 02... 22 ee ee se 3 100 Me
CRITE: CGI Se eR PS 5 80 20
Candong stemoides...-: 2... 062.222 + 52 100
The frequency with which ostracods may be collected without regard
to bottom or vegetation throughout a given pond, lake, or stream may
be shown by the following two examples taken from many similar
instances in the writer’s data:
(1) On June 4, 1940, four samples were taken from Twin Lakes at
Paris, Edgar County, Illinois. One sample was made from a mass of old
leaves in water eight inches deep over a mud bottom where there was
no aquatic vegetation or algae; a second collection was made in water of
about the same depth where there were many aquatic plants and consider-
able algae; a third sample was taken above a rock bottom in mixed algae
and decaying vegetation; and the last was a surface sample where the
water was two feet deep. Each of the four samples contained the follow-
ing three species: Cypridopsis vidua, Potamocypris smaragdina, and
Physocypria pustulosa.
24 ILLINOIS BIOLOGICAL MONOGRAPHS
(2) In three samples taken from a drainage ditch near Rantoul,
Champaign County, Illinois, on June 20, 1940, Limnocythere reticulata
was found abundant. The samples were taken as follows: the first from
a backwater area with decaying corn stalks over a silt bottom; the second
from along the edge of the stream in grass overhanging the mud bank
where there was some current; and the third was from masses of algae
clinging to the gravel bottom of a pool under the highway bridge.
While the distribution in any habitat of most of the species present is
very general, some species, as many Candona species, are sometimes
found isolated in definite regions. No logical excuse for such localization
has appeared in the writer’s data. A detection of many of the minor
environmental factors which play a role in distribution probably will be
discovered only by detailed laboratory experimentation. It is safe, how-
ever, to state that in general the more common species are limited in their
habitat range only by the generalized conditions expressed in still
temporary waters, permanent still waters, temporary running waters, and
permanent running waters or by much finer analysis of environmental
conditions than has even been possible in field studies. The distribution of
species according to the type of habitat is shown in Table 1. By refer-
ence to the table, it will be seen that there are certain species apparently
characteristic of each of the four types of habitats, others which occur in
combinations of two or three habitats, and some that are found in all the
types of habitats. While there is a fair degree of consistency in habitat
relations for many of the species, the association is not absolute. In the
same manner that species serve as index organisms in other biological
phenomena, these species are not always immutable indices to specific
habitat conditions. The kinds of habitats or combination of habitats with
the characteristic ostracod species* of each may be listed as follows:
(1) Ostracods chiefly of vernal ponds:
Candona distincta Candona fossulensts
Candona indigena Cypricercus reticulatus (usually)
Candona suburbana
(2) Ostracods chiefly of permanent lakes:
Candona crogmaniana Notodromas monacha
Cyclocypris forbesi Darwinula stevensont
Physocypfia pustulosa (usually) Limnocythere verrucosa
Cypricercus tuberculatus
(3) Ostracods typical of temporary streams:
Candona punctata Candona fluviatilis
(4) Ostracods typical of permanent running waters:
Candona sigmoides
(5) Ostracods found in both temporary and permanent still waters:
Cypria ophthalmica
*Because of the incompleteness of the data of former workers, only those ostracods are
shown here that were actually observed by the writer in the course of his field work. What is
known regarding the ecology of any other species recorded for Illinois may be found under the
species description.
OSTRACODS OF ILLINOIS—HOFF 25
(6) Ostracods collected chiefly in both temporary and permanent running waters:
Candona acuta Cyprinotus incongruens
Ilyocypris bradyi Limnocythere reticulata
Ilyocypris gibba
(7) Ostracods found in temporary still and running waters:
Candona albicans Candona biangulata
(8) Species found in three or more kinds of habitats:
Candona simpsoni Cypria obesa
Candona caudata Cypria maculata
Cypria turneri Cypridopsis vidua
Cypria mediana Potamocypris smaragdina
Except for the species which have been taken in but one or two col-
lections, little change in the knowledge of the habitat of any species should
be effected by additional collections. At the same time, many of the
records based on a single sample are no doubt accurate, since they repre-
sent species which are known to be limited in their range of habitat.
PHYSICAL FACTORS IN THE HABITAT
While the distribution of ostracods appears to be limited grossly by
the type of habitat rather than certain single isolated environmental fac-
tors, there is a slight correlation between some of the physical factors and
the occurrence of certain ostracod species. According to P. R. Needham
(1938), there are five physical conditions which largely determine the
distribution of aquatic organisms. These are (1) type of bottom;
(2) velocity of current; (3) depth of water; (4) temperature of water ;
(5) materials in suspension and solution. Of these factors, two were
recorded in considerable detail in the field notes. These were (1) type
of bottom and (2) the amount of current. Since most of the collections
were made from shallow ponds and streams and from the littoral zone
of the larger bodies of water, the depth showed no distinguishable effect
on the distribution. Roughly speaking, the writer’s experiences in the
field seem to indicate that the limited temperature ranges found in Illinois
also have little effect on the distribution of species of ostracods. Although
some species are inhabitants of cool vernal ponds or the larger, cooler
lakes of northern Illinois, there seems to be, offhand, no indication that
water temperature is in any way causal to the distribution of ostracod
species. The effect of temperature on the life cycle and activities of
ostracods can, perhaps, best be approached from an experimental point of
view before any definitive effect can be ascertained under natural condi-
tions. As a result of the limited time allowed for this study and the
difficulty of carrying and using elaborate apparatus which would have
hindered the rapidity necessary for collection of a large number of field
samples, no effort was made to test the turbidity of the water or to
determine the materials in solution. The hydrogen ion concentration,
26 ILLINOIS BIOLOGICAL MONOGRAPHS
however, was determined on about one-fourth of the samples secured.
No more tests were made since, as a rule, the waters of the northern two-
thirds of the state are alkaline. A number of tests were made to check
the character of the water in the southern portion of the state where it is
often acid especially in Franklin, Johnson, and Massac Counties.
Kind of Bottom.—In regard to the effect of the type of bottom on the
occurrence of ostracods, no very definite correlation has been found in
most species, and the distribution appears usually to be random as far
as the type of bottom is concerned. As the proportionate number of times
in which a species was found associated with different types of sub-
stratum was usually about the same as the number of times samples were
taken from the same type of substratum, no correlation between range and
type of bottom is evident in most cases. Many of the Candona species
show a slight correlation with the type of bottom, a more-than-average
number of collections being made on a mud bottom for many of the
species. This is related, no doubt, to the occurrence of many Candona
species in temporary waters where mud is usually the substratum en-
countered. Besides, most of the Candoninae crawl on the bottom, and
mud is more favorable for animals of such a habit than is a sand bottom.
Three species besides those of the genus Candona show a tendency to be
associated with a particular type of bottom. These species are listed
below with the percentages of incidence over various substrata along
with the percentage for comparison of each type of substratum in the
total number of collections. Hard “Siageon
Mud clay gravel Rock
CY PAGEL CUS HELMCUIGIUS Se Meee oe ete eye: 100% 0% 0% 0%
Cyprinotusincongruens: ee. 4-2 ase 59 0 35 6
Potamocypris smaragdina.............---.+--- 49 B) 36 10
Average of all collections.................-..-. 73 4 19 5
Since all thirty-two of the collections of Cypricercus reticulatus were
found over a mud bottom, it is obvious that this species is somewhat
similar to the Candona species already mentioned. Like many of the
Candoninae, this species is an inhabitant of temporary waters. Why there
should be an increase over the average of incidence in the case of
Cyprinotus incongruens on a sandy bottom is not known, but in the case
of Potamocypris smaragdina the increase of a sand and gravel bottom as
a substratum may be the result of this species occurring in great abun-
dance in permanent waters where sand and gravel shores are common.
Hence the type of bottom is a limiting factor in very few species but
rather an incidental factor related to the habitat in general.
Current.—In contrast to the relegation of the type of bottom to a
minor position as a factor in the distribution of ostracods, there is a
marked relationship between the velocity (as measured by inspection
OSTRACODS OF ILLINOIS—HOFF 27
TABLE 2
Table showing incidence, expressed in percentages, of each species observed by the
writer in varying conditions of current. The name of each species is followed by the
number of collections in which it occurred.
Collec- No Little Much Swift
Species tions | current | current | current | current
Gnndond punciaia...... 2... 0.00660 55 1 100 J =
Candona crogmaniana.............-- 2 100 Be ot
ROTETELOMUNGTSILICLO nce ccc eo ot sic eee 3 100 es Se
Candona indigend..-.. 1... 061 te eee 4 100 : ba
Candona suburbana.....:.........-- 2 100 A ie
Candona fossulensts .\. 00.0200. eee 2 100 Eas 08
GNGIOGY PITS FOTDEST.. 6 oe cc sie ele els 1 100 fe Ss
COU TTORINCAIONG 0.5. ie cle eee 8 aa 3 100 - -
Cypremophinalmica...... 0... cses 8 100 a Se
Cypricercus tuberculatus.............. 3 100 = ae
Notodromas monacha...............- 1 100 ne Aes
Darwinula stevensont................ 1 100 a: ie
Limnocythere verrucosd............45- 4 100 ie Me ee
eh. ac Vins fais dl ve os 9 78 22 a
Candona brangulata... 2.08 ee ce et 5 60 40 SE a
CAMMOROROLDIGCONS.. 6 oo. ook ne cose oe 4 75 2 25 Se
CONDON GOUGOIA «Keo. is ne 3 67 4 33 Be
ef er 28 94 3 3 _
Physocypria pustulosa............... 172 92 7 1 A
Cypricercus reticulatus............... 30 90 7 3 Ae
CN AGINOCUIOIG. 6 hei. Shales Annie 42 64 24 12 a
Cyprinotus tncongruens.............. 16 31 38 31 he
EN PHIGOPSISIAUG oo bs 5 Sys ee 8 aa o's aoe 500 80 16 3 1
Candona/Stmpsont.......... 6.0.0 c aes 84 79 14 5 2
Potamocypris smaragdina............ Lily 68 30 1 1
Limnocythere reticulata............... 70 50 26 20 4
HESESY LIS G0 eae ae ee 42 Dil. 48 18 7
WUNGENPIESIULOGDYU 12 6 one 26 caahsis oases 72 26 44 24 6
Cs ALTO NCTA eee eee ene nee 5 20 40 20 20
Gandona fluviatits ro 3. eee bc ks 3 Be 100 i a
Candona sigmoides.............0.:55: 4 at 50 DS 25
only) of the flow or the absence of current and certain ostracod species.
From Table 2 it may be observed that while most of the species investi-
gated are abundant in quiet water, many of these same species tolerate
varying rates of flow. Certain species, however, are confined almost with-
out exception to water in which there is no current. Although the number
of collections of most Candona species are relatively few, there is con-
siderable evidence that the following species are chiefly confined to quiet
waters: C. crogmaniana, C. distincta, C. indigena, C. suburbana, and
C. fossulensis. Three species of Cypria, C. turneri, C. mediana, and
C. ophthalmica, belong also in habitats in which there is no current.
Cypricercus tuberculatus, Notodromas monacha, Darwinula stevenson,
and Limnocythere verrucosa have been taken only from the still waters of
northern lakes. Two common species, Physocypria pustulosa and Cypri-
cercus reticulatus, are seldom taken from flowing waters. Areas which are
28 ILLINOIS BIOLOGICAL MONOGRAPHS
subject to considerable wave action appear to be no different as far as the
ostracods are concerned than areas of quiet water. This is easily con-
ceivable since many of the ostracods live in the plant zone where the
action of the waves is not pronounced.
While certain species of ostracods are found usually in quiet waters,
other species occur more abundantly in flowing waters. Candona fluviatilis,
C. sigmoides, and C. acuta are common in running water, the last two
species sometimes being found where the flow is swift. Among the species
most typical of streams are Ilyocypris gibba, I. bradyi, Cyprinotus incon-
gruens, and to some extent Limnocythere reticulata. A few species which
are usually found in still water, are frequent also in a little current and
some may even tolerate swiftly flowing water at times, especially during
flooded conditions. Two of these, Cypridopsis vidua and Potamocypris
smaragdina, sometimes are-found in rapidly flowing water, although they
are more abundant where there is no current.
The velocity of flow is no doubt a limiting factor in the distribution of
many ostracod species. Many of the forms living in areas where consider-
able current is found are adapted by having the antennae modified for
creeping rather than swimming. A rather large shell, rectangular, com-
pressed, and sometimes ornamented by furrows or protuberances seems to
be characteristic of species living in running waters. On the other hand,
active swimmers as most of the Cypria species, Cypridopsis vidua, Physo-
cypria pustulosa, and Potamocypris smaragdina seem adapted to quiet
water, since they have well developed swimming setae, often tumid shells,
and have little ability to maintain themselves against strong currents.
Hydrogen Ion Concentration.—The only other physical factor given
consideration in the field was the hydrogen ion concentration. Most
species do not appear to tolerate waters which are strongly acid in
reaction. This is especially true of the species with large, heavily calcified
shells. Such forms, as many of the Candona species, Cyprinotus incon-
gruens, and the two Illinois species of Ilyocypris are included in this
group. On the other hand, many of the Cypria species tolerate acid
conditions, and these include for the most part species which have small
shells apparently protected by a heavy organic covering as evidenced by
color and texture. Many of the Cypria forms as well as Physocypria
pustulosa and Cypridopsis vidua fall into this group. Because of the acid
nature of the water in the extreme southern part of Illinois, the writer
believes that the absence there of many species elsewhere common may be
explained on the basis of their intolerance to the acid environment. Two
species of Cypria, C. mediana and C. ophthalmica, are, on the other hand,
absent from the northern half of the state, and since they are forms which
tolerate an acid condition, it is possible that the conditions are not
OSTRACODS OF ILLINOIS—HOFF 29
proper for their continued propagation in the highly alkaline lakes of
northern Illinois.
It is regrettable that data relative to other physical factors could not
have been collected for analysis, but this was impossible with the limited
time available. As a result, however, it is possible to state that, on the
basis of the data at hand, there are certain species of ostracods confined
more or less to definite habitats and that in general the distribution of
ostracods is limited, to some extent at least, by the velocity of the current
and the hydrogen ion concentration of the water. Other physical factors,
such as the nature of the bottom, appear to have little to do with habitat
selection.
Biotic RELATIONSHIPS
At the beginning of this investigation, the writer held the preconceived
idea that there might be species of ostracods characteristic of different
plant associations and species which might be commonly associated
together. The data collected in the field failed to verify either of these
ideas. A few species show higher incidence, however, on bare bottom or
as a constituent of plankton than do other species.
As mentioned in the introduction, ostracods are not important as
plankters, in spite of the statement by Welch (1935) to the contrary.
Some species, it is true, are occasionally found in open water plankton
samples (Table 3), but they are of such minor importance that they are
not mentioned by Eddy (1934) in his study of fresh-water plankton
communities. Kofoid (1908), in one of the most intensive surveys ever
made on the plankton of a river system, lists a few species found in
plankton from the Illinois River at Havana, Illinois. He found Candona
simpsoni “occasionally adventitious” in plankton samples. This is rather
peculiar as the Candona species are not very natatorial, since they lack
swimming setae on the antennae. Kofoid’s record of this species in
plankton is substantiated by the records of the present writer who has
found the same species occurring as a plankter. Kofoid also reported
Cypria ophthalmica and Cypridopsis vidua as common and Cypria ex-
sculpta (= Cypria turnert) and Cypria pustulosa (= Physocypria pustu-
losa) as rare in plankton. He also collected a typical bottom form, Limno-
cythere reticulata, in the plankton at the time of flood waters. Cypria
turneri and Physocypria pustulosa reached the highest incidence of all
those species found in plankton in the writer’s samples. Of these, the
first was taken as a plankter in seven per cent and the second in six per
cent of the samples in which they occurred. Cypria maculata, Cypridopsis
vidua, Potamocypris smaragdina, and Candona simpsoni may also be
taken occasionally in areas of open water. It will be noticed that the
ostracod species found in plankton are, more often than not, active
30 ILLINOIS BIOLOGICAL MONOGRAPHS
TABLE 3
Table showing the incidence, expressed in percentages, of certain species found in
collections from bare bottom areas, in plankton, and associated with different kinds of
vegetation. The name of each species is followed by the number of collections in which
it occurred. (Aqua. vege. = Aquatic vegetation (Spermatophytes); Dec. vege. =
Decaying vegetation.)
Bare
. Collec- Aqua. Dec. | Plank-
Species tions 2 ot- | Grass vege. Alga vege.| ton
om
Candona biangulata.............. 5 60 40 ae at
Cyprinotus incongruens...........- 18 11 39 35 50
(Cy PIVOHOUCSI An ames «ret eee 11 9 37 36 18 +
Cypria ophthalmica............... 10 10 40 he 30 20 B
Ilyocypris gibba............-4000- 47 15 42 6 28 9 a
Ilyocypris bradyt..............4-- ou 10 35 13 29 13 me
Limnocythere reticulata............ 79 8 35 10 27 20 re
Ci Prta urnere sn ees ke ee 29 14 31 14 17 ily/ 7
Physocypria pustulosa............ 188 8 19 30 31 6 6
Candona simpsont...........-.++-- 93 6 44 10 29 9 2
Cypridopsis vidud.............+-. 537 4 30 24 30 9 3
CYPTAGMACUIAIG opie ose ee 48 2 32 20 40 2 4
Potamocypris smaragdina......... 126 2 21 29 40 6 2
Candona albicans...............- 6 ae 50 ae 50 a8
Cypricercus reticulatus............ 32 a 50 46 16 34
COndGnanaCUiie soe ee 5 et 20 20 20 40
swimmers with a small and plump shell. Certainly they do not breed in
open water and are, as Kofoid states (1908), completely adventitious in
plankton, since they are apparently derived from vegetation-covered areas
near shore or in backwater lakes.
Candona biangulata appears to be the only ostracod found in the
majority of instances on bare bottom. The factor responsible for this trait
cannot, at present, be determined but may be related to food habits about
which little is known. In general, the association of most species with
different types of vegetation deviates little from the average for all the
collections. A very limited number of species are absent from associations
dominated by aquatic plants. These include Candona albicans, C. biangu-
lata, Cypria ophthalmica, Cypricercus reticulatus, and Cyprinotus incon-
gruens. This lack of average incidence of association with aquatic
spermatophytes may be explained in some instances by the fact that
Candona albicans, C. biangulata, and Cypricercus reticulatus are inhabi-
tants only of temporary waters and as a result do not have occasion to
become associated with aquatic seed plants which reach a high degree of
development in permanent waters. In the same way, it is possible that
Cyprinotus incongruens has little opportunity for more than mere chance
association with such plants, since it is chiefly an inhabitant of running
waters where water plants are not abundant. It is difficult, however, to
OSTRACODS OF ILLINOIS—HOFF 31
explain the absence of Cypria ophthalmica from the aquatic vegetation
since it is entirely a species of still waters, both temporary and permanent.
However it is unsafe to venture the opinion that the presence of aquatic
vegetation limits the distribution, since the number of samples in the case
of C. ophthalmica is relatively small and the range of this species does
not include northern Illinois, where a majority of the collections from
aquatic vegetation was made. It appears then that there is no conspicuous
relationship or specific association between certain species of ostracods and
certain types of vegetation other than what might be legitimately expected
as incident correlations resulting from reflections of the general habitat
and range of the species.
The writer gave special attention to the ostracods taken from growths
of various species of aquatic plants especially in the lakes of Lake and
Cook Counties in an effort to determine if any relationships existed
between certain species of ostracods and specific water plants. Most of
the collections used for this particular part of the study were made by
Bertrand A. Wright who supplied the identification of the plants. A few
examples of this type of data, showing the plants present where various
ostracods were found may be assembled as follows:
(1) West Loon Lake, Lake County, Illinois; August 7, 1940:
Potamocypris smaragdina........
Cypridopsis vidud.........0.0000% | Chara sp.
Limnocythere verrucosd......... ;
Potamocypris smaragdina........ Chara sp.
Cypridopsis vidud........cr00.ees
Limnocythere verrucosd..........
Potamocypris smaragdina........ Chara sp. and Potamogeton natans
EMpridOPSts VidUd,...-- 2.000055.
Potamocypris smaragdina........
| allisnert ;
Limnocythere verrucosd.......... A rua sp
Potamocyfris smaragdina........
Cypridopsis vidua...........0004. | P otamogeton: crspus and Fnatans
Potamocypris smaragdina........
Limnocythere verrucosd..........+
(2) East Loon Lake, Lake County, Illinois; August 7, 1940:
Potamocyfris smaragdina........
CypmadOpsiSactduds. oenescsc ese. oi
Chara sp. and alga
Chara sp. and Potamogeton natans
Potamocypris smaragdina........
Cypridopsis vidud........0s0.000-
Physocypria pustulosa...........
Cypridopsis vidud........0...0++-
Ceratophyllum sp.
White water lily and Myriophyllum sp.
Cy pradOpsts. VIdUGs. .606.0.0005005 2% Spirogyra sp.
Chara sp., Myriophyllum sp., and
CYCLOCYPTAS fOTOCSt-... ose none Parmancetomed:
Potamocypris smaragdina........
CNPTid OPSISsUUA eee estes oboe
32 ILLINOIS BIOLOGICAL MONOGRAPHS
Potamocypris smaragdina........
Cypridopsis vidUud ae eere ese ene | Potamogeton crispus and Chara sp.
(3) Lake at strip-mine area, Vermilion County, Illinois; September 19, 1940:
Cypridopsts UWidud.....0. 50.00.55
Potamocypris smaragdina........ | Alga and Sago weed
CYpridOpsis DOUG cis. USis.one ewes ae Dianthera americana
Cupridopsis” VIdUG: vols ssa ceeaice ec Sargasso weed
CYPLIGOPSUS "OIOUG tec k we hile ws oe ee Ceratophyllum sp.
These data illustrate admirably the condition found in lakes in general.
The ostracod species show no distinct favoritism for certain plants and
appear not to be a part of any particular association. It will be seen that -
in only two instances are there species in a given collection that do not
occur in several other collections from the same lake on the same date.
For one of these, Cyclocypris forbesi from East Loon Lake, this is the
only time it was taken during the entire field investigation and so has
little significance here, since its occurrence in the state is rare. Likewise,
the presence of Potamocypris smaragdina in the strip-mine lake is prob-
ably insignificant as far as associations are concerned, since it is found
associated with all kinds of plants in both East and West Loon Lakes.
An examination of the data was also made to determine if the species
of ostracods formed associations among themselves. It was thought by
the writer that such information might be useful in proving that there
are certain environmental factors which govern the distribution of
ostracod species. If it were possible to show that certain species of
ostracods were always associated together, it would be sound evidence
that environmental factors limited ‘the distribution of groups of species
reacting similarly to the same limiting factors. A close study of the
incidence, in which certain species occurred together, showed no signifi-
cant correlation indicative of any inter-group associations. The data are
too bulky to give in detail here and too insignificant to merit detailed
discussion. Apparently association of two or more species is largely by
chance, except as such associations are made up of species which are
characteristic of one of the four kinds of habitats already described.
Thus Ilyocypris spp. and Limnocythere reticulata are often found asso-
ciated together in running water.
As an incidental observation, the writer found that protective colora-
tion appears to be well developed in many of the ostracods, especially in
species of Cypria, Physocypria pustulosa, Cypridopsis vidua, and Potamo-
cypris smaragdina. These species are commonly of varying shades of
cream or light green, with blotches of dark green, brown, or black. Since
these species are usually found swimming in aquatic vegetation, alga, and
grass growing in the water, it is reasonable to suppose that the coloration
affords them some protection from predatory animals. On the other hand,
OSTRACODS OF ILLINOIS—HOFF , 33
other species of ostracods, especially species of Candona and Ilyocypris,
are usually light in color, white to yellow, and are unmarked with stripes
or blotches of deeper color. It may be that species such as these which
live in temporary waters or creep over the bottom or through the mud in
running waters are not subject to the same dangers as are species of
ostracods which swim freely in the vegetation and so are apt to be eaten
by plankton-consuming fishes.
SEASONAL DISTRIBUTION
Many of the ostracods of Illinois are seasonal in their occurrence.
This is especially true of certain species which appear during the pre-
vernal and die out in the aestival season. Other species are not found
until the vernal or even the aestival season. The seasonal distribution of
species collected by the writer is shown in Table 4. Since the writer has
very few collections in the autumnal and none in the haemal seasons,
the months from September to February inclusive are not shown in the
table. Little is known of the American ostracods found during the winter
months. From the fact, however, that many species are found in the
prevernal season only as larvae, it is apparent that the number of species
passing the winter in the adult stage is limited.
Since the seasonal distribution of the writer’s collections was limited,
the records of Sharpe (1897, 1908) have been taken into consideration,
as indicated in the explanation to the table. By the amount of additional
information given for several species by Sharpe’s records, it is evident that
the data on seasonal distribution are far from complete. A certain amount
of valuable information, however, can be obtained from a study of the
table. In the first place, it is evident that certain species are found
typically in the vernal and early aestival seasons. These species include
many of the Candona, especially those which are characteristic of
temporary waters as Candona fluviatilis, C. distincta, C. indigena, C. sub-
urbana, and C. fossulensis. Other Candona species are either scattered
(as C. albicans, C. biangulata, and C. punctata) in such a way as to make
the record insignificant or they are to be found during most of the year,
as is C. simpsoni (Kofoid 1908). Of the Cypria species, Cypria turneri
and C. ophthalmica are apparently found during the entire period from
March to August inclusive. C. maculata shows the same distribution.
C. obesa is evidently typical of the aestival season and later. Besides many
of the species of Candona, Cypricercus tuberculatus and C. reticulatus
appear to be forms which die out before the first of July. In addition to
the Cypria species mentioned above, Physocypria pustulosa and Cypridop-
sis vidua are found throughout most of the entire period investigated.
Potamocypris smaragdina apparently reaches its highest abundance in the
34 ILLINOIS BIOLOGICAL MONOGRAPHS
TABLE 4
Seasonal distribution as shown by the months in which each species was found. Since
few collections were made in the months from September to February inclusive, these
have not been shown. The name of each species is followed by the number of collections
in which it occurred. The relative abundance of various species in the different months
is indicated as follows: x—rare; xx—common; xxx—abundant. For the advantage of
additional information, the records of Sharpe (1897, 1908) are indicated by the letter ‘‘y.”’
Species raed Mar. | Apr. | May | June | July | Aug.
ions
Candona simpsont..............+.- 85 XX XXy | XXXy | XXX XxX x
Candona punctata................ 2 x rt » x ye
Candona fluviatilis: . 62.42 -2. 2 ee 3 x x oe
Candona albicans.............+..-- 4 x os XX
Candona biangulata.............. 5 x xy x Be x
Candona crogmaniana............ 2 x a ee oF
Candona sigmoides............... 4 oe y xe a8 cx.
Candona caudata................-- 4 x x Be. ne ae
Candona distincta..........-..--- 3 x x ie us :
Candona indigenad................ 4 x Xi ds ae
Candona suburbana.............. 2 e x x nee
CHPLOBE CENT. ce5000060300000006 6 Bs XX fe D4
Candona fossulensis.............. 2 x i ie a
Cyclocy pros forbest.---245-2-4- 4. - 1 x: y sie x
Cyprian Uunnerime eee eee ee 30 xy y xxy | xxy xy xy
COMODO TABU BO. coconon0s00000000 5 ae ie fe x be
(CWE OUR. oo edob oes goebaccase 9 ae a x x y
Cypria maculata..............4.. 43 y y xy XX xy xy
Cypria ophthalmica............... 9 xy y xy xy y xy
Physocypria pustulosa............ 175 as x xy eee || SOG7 || Yesy
Ilyocypris gibba.... 0.1.0... eens 44 ons ait XX XXX x xs
Ilyocypris bradyt.............000. 72 af a Xxx | XXX XX x
Cypricercus tuberculatus........... 3 = y y x
Cypricercus reticulatus............ 32 xi xy XX x
Cyprinotus incongruens........... 16 a wh x x x
Notodromas monacha............. 1 th: y y xy y(?)
Cypridopsts vidua................ 505 xy xy xy | xxxy | xxxy | xxxy
Potamocypris smaragdina......... 118 eg hy x XXX XxX | XXXy
Darwinula stevensont............. 1 ie ue Ny te 7 x
Limnocythere reticulata............ 70 y XX XXX x x
Limnocythere verrucosa............ 4 a a. sa a x x
aestival season. The status of the two Ilyocypris species cannot be
determined from the field data, since few collections were made by the
writer from streams during March and April, and the flooded condi-
tion of streams at this time makes results untrustworthy. That the absence
of these two species from the vernal collections is more apparent than
real may be suggested by Sharpe’s record (1908) of these two species
from Colorado in March. Alm (1916) states that J. gibba and I bradyi are
found throughout the year, there being two generations. However, this
does not necessarily mean that there are two generations each year in
Illinois, especially since Alm states that the species in Sweden do not
favor temporary waters. In Illinois, approximately one-half of the col-
lections of these two Ilyocypris species were from temporary streams.
OSTRACODS OF ILLINOIS—HOFF 35
°
REPRODUCTION AND ONTOGENY
No work has ever been done on the life histories and reproduction of
American species except by Turner (1895) who made a study of the late
larval stages of Cypris herricki Turner 1892, which is a synonym of
Chlamydotheca speciosa Dana 1852 according to Furtos (1933). European
writers have, on the other hand, published much on the development,
reproduction, and life history of various species. Some of these studies
are founded upon data secured from animals reared and observed in the
laboratory (as Claus 1872); others such as the work of Alm (1916) are
based largely on field collections. The writer believes either method alone
to be relatively deficient and that the acceptable manner of investigation
would be a preliminary study by either field or laboratory methods
checked by the other method.
In general, the ontogenetic development of fresh-water ostracods is
similar in different species, especially among the Cypridae. During de-
velopment, nine instars occur, the last being the sexually mature animal.
Claus (1872) worked out all the stages in the development of two Euro-
pean species: Cypris ovum (= Cyclocypris ovum (Jurine 1820)) and
Cypris fasciata (= Dolerocypris fasciata (O. F. Miller 1776)). Claus
found that the egg hatches into a shelled nauplius with three pairs of
appendages, two representing the antennules and antennae, the third the
mandibles. In general, a pair of appendages is added at each molt, with
the furca appearing as two bristles in the fourth instar. Schreiber (1922)
made a study of the larval stages of Cyprinotus incongruens. His results
are slightly different from those of Claus. A comparison of the time of
appearance of the appendages in the three species mentioned follows:
PAIRS OF APPENDAGES
Cypris ovum; Cyprinotus
Instar C. fasciata incongruens
MMR ANTTDULNTS)) Since ae clsc® yo SG bus wi shans oe Stokke a weds 3 3
EP tapi = RETA aia ates tye ee oad fee SRS a Pel le 5 4
Soa 7 ole & ORs BORER Agena el RSS Ae Re or 5 5
isa + hd dS Senet Sea ell gee DS a 6 5
Sia 15 6/5 Sick a RAO ER aes age ec ea 6 6
Us NE eR to Se ons 2 pions Sieg awe ori 7 7
If a single pair of appendages were added in each stage as probably oc-
curred in the ancestors of the group, it is evident that the sixth stage
would have eight rather than seven pairs of appendages. Many writers
account for this irregularity by assuming that the second maxillae which
are present in many crustacea have been lost in the ostracods.
Not only is there an increase in the number of appendages at many
of the earlier molts, but differentiation of the appendages occurs up to the
late stages. Claus (1872) found that the antennule, for instance, of the
36 ILLINOIS BIOLOGICAL MONOGRAPHS
nauplius has four podomeres, another is added in the fourth instar, one
more in the sixth, and still another in the seventh. The antenna of the
nauplius has two podomeres, in the sexually mature animal (ninth stage)
four, and in all other stages three. The legs and furca also begin as
undifferentiated structures and pass through several instars before the
adult condition is reached. The second leg, for example, has one podo-
mere when it first appears in the second stage. Three podomeres are
added in the sixth instar; in the seventh stage there is an additional
podomere. The anlagen of the gonads are conspicuous in the seventh
instar; the copulatory organs are present in the eighth instar; and the
animal reaches sexual maturity in the final stage. The development in
the Cytheridae is grossly similar to that of the Cypridae (see Klie 1926a).
Not only do the appendages increase in number and change in form,
but the shell becomes altered in shape in various instars. This has often
led to a description of the young as a new species (see “remarks” under
Cypricercus reticulatus). In many species, the sculpturing of the young
shell differs from that of the adult, and there are differences in coloring
as well. An extreme difference between young and old shells is shown in
Cypris labiata Sars 1901 (= Chlamydotheca incisa (Claus 1892)) in
which Sars (1901) has shown that the young shell lacks the hyaline lip-
like expansion of the anterior margin as found in the adult. The young,
moreover, has a row of small denticles along the posterior margin of each
valve not found in the adult. Turner (1895) found much the same condi-
tion in his Cypris herricki already mentioned. A series of drawings by
Alm (1916:pl.1) shows the shell changes in several species common in
Sweden. As far as the writer knows, no work has been carried out on the
early stages of even the common species in North America.
In order to complete the references regarding development, mention
should be made of the work of Miiller-Calé (1913) in which the early
embryology through the germ layers is considered. Reference may also be
given to investigations on the development of eggs and sperm, chiefly that
of Woltereck (1898), Schleip (1909), and Schmalz (1912).
The manner of reproduction in ostracods varies considerably in differ-
ent species. Roughly speaking, the ostracods may be divided into four
groups as far as type of reproduction is concerned:
1. Males unknown; reproduction apparently always parthenogenetic:
Candona fluviatilis Cypricercus fuscatus
Candona simpsom Cyprinotus pellucidus
Candona biangulata Cypridopsis vidua*
Candona caudata
_ “Sharpe in 1918 considers C. vidua as being temporarily parthenogenetic. The present
writer has seen no males, and only one record (Spandl 1925) of the occurrence of males is
Con This report is questionable and has been called ‘“unglaubhaft” (unbelievable) by Klie
a).
OSTRACODS OF ILLINOIS—HOFF on
2. Males found in a few localities, usually absent; reproduction ordinarily
parthenogenetic: ’
Candona albicans Cyprinotus incongruens
Ilyocypris gibba Darwinula stevenson
Ilyocypris bradyi
3. Males found in small numbers; reproduction supposed to be both syngamic and
parthenogenetic:
Cypricercus reticulatus Potamocypris smaragdina
4. Males always present; reproduction thought to be syngamic:
Candona punctata Cypria mediana
Candona distincta Cypria obesa
Candona crogmaniana Cypria maculata
Candona sigmoides Cypria ophthalmica
Candona recticauda Physocypria pustulosa
Candona sharpei (?) Physocypria dentifera
Candona indigena Cypricercus tuberculatus
Candona suburbana Notodromas monacha
Candona fossulensis Cyprois marginata
Candona acuta Limnocythere reticulata
Cyclocypris forbesi Limnocythere illinoisensis
Cyclocypris sharpet Limnocythere verrucosa
Cypria turnert
For details of the occurrence of males in groups two and three above, the
reader is referred to the separate species descriptions given herein.
It will be noticed by reference to the last group above that a majority
of Illinois species are syngamic. This group includes all the members of
the family Cytheridae and many of the Cypridae. It is peculiar that many
subfamilies of the Cypridae fall into more than one group as far as
manner of reproduction is concerned. This variation precludes the pos-
sibility of using the manner of reproduction as a generic or specific
criterion, since it is not related closely to the morphological structures
used in classification.
That the method of reproduction varies in different localities is shown
by Klie (1926a) regarding Cyprinotus incongruens. Males of this species
have been found rarely in Germany and occur more frequently in
Hungary and Bohemia. In North Africa, however, the males are as
abundant as the females.
A definite alternation of periods of syngamic and parthenogenetic
reproduction has not been shown in the ostracods. Wohlgemuth (1914)
found a change from one type to another in populations under investiga-
tion in nature and in the laboratory. Whether or not an alternation similar
to that in many Cladocera occurs or not is uncertain.
All the ostracods in Illinois are oviparous except Darwinula stevensoni
which retains the eggs during development in the posterior dorsal part of
the shell cavity. The eggs of oviparous species are usually attached to
some substratum, especially plants, where they may undergo develop-
ment at once or may remain, as in temporary ponds, for several months
38 ILLINOIS BIOLOGICAL MONOGRAPHS
surviving a period when the pond is entirely dry. The eggs are also able
to withstand freezing. Because of the ability to withstand desiccation,
Sars (1895, 1896, 1901) often imported mud to Norway from South
America, Africa, and Australia. This mud was placed in aquaria and the
ostracods allowed to develop. In this way, Sars received material not
otherwise available.
The number of generations per year varies from one to many in
different species. The best available example of a local species with a
single generation each year is Cypricercus reticulatus which is chiefly an
inhabitant of temporary ponds. The eggs hatch sometime during the
month of March at the latitude of Central Illinois. The larval stages may
be recognized by the characteristic shell reticulations which are absent in
the adult. The larvae develop rapidly, and early in May the individuals
become sexually mature, lay their eggs, and die. No immature individuals
are ever found after the first week in May. Several other ostracod species,
chiefly those living in temporary ponds, also have one generation per year.
Many of these are species of Candona which, as a result, have a limited
seasonal distribution.
On the other hand, many species have a larger number of generations.
Alm (1916) often assigns a particular number of generations to a certain
species, but the writer feels that his results should not be carried over
without verification to the same species in North America, since there is
apparently much variation under different environmental conditions. How
many generations occur each year or the length of life-span are uninvesti-
gated for American species. The present writer has observed that in
Cypridopsis vidua, Potamocypris smaragdina, and probably some of the
species of the subfamily Cyclocyprinae young are found nearly continu-
ously during the summer. This would probably place these species among
those with numerous generations each year.
Foop
Food and feeding in the ostracods have been given little attention by
investigators. The food of few species has been studied in detail, although
a study of the food habits might have some bearing on problems of
distribution. In Europe, a very detailed study of the mouth parts and
method of feeding in a single species has been carried out on Notodromas
monacha by Storch (1926, 1933). Most species feed on bacteria and other
minute organisms as well as detritus. Klugh (1927) in feeding experi-
ments on Cyprinotus incongruens, Cypridopsis vidua, and Cypria exculpta
(?=C. turneri sp. nov.) found that the animals ingested both algae and
detritus, but in most instances thrived better when fed the former. Since
the mouth parts are setaceous, they are well adapted for straining minute
OSTRACODS OF ILLINOIS—HOFF ~— 39
organic particles from the water and forcing them into the mouth. At the
same time, the mouth parts, especially the mandible, are capable of rasping
material from solid bodies too large to be ingested. Many species, as some
of the Candona species, apparently ingest large numbers of diatoms which
they seem able to digest, since the cytoplasm within the test of the
diatom stains when the plant is first ingested but only the empty test may
be observed in the food balls in the posterior part of the intestine. In
contrast to the smaller swimming species as Cypria spp., Cypridopsis
vidua, and Potamocypris smaragdina, which feed on minute organic
particles which they strain from the water, Klie (1926a) states that the
larger species of Cyprinae often collect in masses to feed on the bodies
of dead animals. It is probable that many of the creeping forms as
Candona spp. and Ilyocypris spp. feed largely on organic materials and
minute organisms in the bottom mud over which they creep.
GCHOGRAPHICAL DISTRIBUTION
OF (OSTRACODS
World Distribution of Species Found in Illinois——The knowledge of
the geographical distribution of ostracods is far from complete as a
result of the lack of information relative to the faunas of many localities.
In general, however, most genera and many species of ostracods are nearly
cosmopolitan in their distribution. Only two well differentiated fresh-
water genera are known to be confined to the Western Hemisphere. The
genus Chlamydotheca* was said by Brehm (1939) to be the only genus
restricted to the Americas. This genus is represented by an abundance
of species in South and Central America and the southern part of North
America. The genus Entocythere, species of which live in the gill cavities
of crayfish, is known only from North America and was apparently over-
looked by Brehm. Another genus, Candocypria Furtos 1933, is known
only from the United States but, since it represents a transition between
two well known genera (Furtos 1933), it seems inadvisable to consider it
as a well defined genus as far as geographical distribution is concerned.
All the genera and many of the species of free-living ostracods found
in Illinois are Holarctic in their distribution. This results in a close
resemblance between European and North American ostracod faunas.
While many of the species are Holarctic in their range, the species of
the genera Candona and Limnocythere are often much restricted, even
though the genera themselves are widespread. In the case of the
Candoninae, this localized condition may possibly be the result of a rapid
*Reports of species of Chlamydotheca from outside the Americas are based on erroneous
generic determination (Klie 1930; Brehm 1932).
40 ILLINOIS BIOLOGICAL MONOGRAPHS
evolution of species occurring at the present time, as is suggested by the
great specific variability and the large number of closely related species
in the group. The following list indicates the geographical distribution of
Illinois ostracods as determined from the literature.
1. Cosmopolitan except Australia:
Cyprinotus incongruens
2. Holarctic and South America:
Cypridopsis vidua Cypria ophthalmica
3. Holarctic:
Ilyocypris gibba Cypricercus reticulatus
Ilyocypris bradyi Notodromas monacha
Cypricercus fuscatus
4. Europe and North America:
Candona albicans Cyprois marginata
Candona caudata Darwinula stevensoni
Potamocypris smaragdina
5. North America:
Cypria turnert Cyprinotus pellucidus
Cypria maculata (?) Physocypria pustulosa
6. United States:
Cyclocypris forbest Physocypria dentifera
Cyclocypris sharper
7. Central United States:
Candona punctata Candona indigena
Candona simpsont Cypria obesa
Candona distincta Cypricercus tuberculatus
Candona crogmanana
8. Illinois only:
Candona fluviatilis
Candona biangulata
Candona recticauda
Candona sharpei
Candona sigmoides
Candona suburbana
Candona fossulensis
Candona acuta
Cypria mediana
Limnocythere reticulata*
Limnocythere illinoisensis
Limnocythere verrucosa
Distribution of Ostracods in Illinois—In general, the ostracods re-
ported from Illinois may be divided into two groups: (1) those having
a more or less general distribution throughout the state and (2) those
limited in their distribution to restricted areas in the state. Most of the
species belong to the first group. Of the species in the second group, the
writer found that certain species occur only in collections from Champaign
County and bordering counties, others are found only in the lakes of
northeastern Illinois, and still others are confined to the southern portion
of the state where the waters are often acid. The localized occurrence
of certain species in Champaign County is not particularly significant
*As explained in ‘‘remarks” under the description of, this species, the record of L. reticulata
for Maine appears to be erroneous as a specific determination. Therefore, L. reticulata is in-
cluded with the species limited to Illinois rather than with those from the United States.
OSTRACODS OF ILLINOIS—HOFF 41
since the writer made an intensive study of the vernal ponds in the region
and, as a result, found species which probably escaped collection in other
parts of the state. Of considerable significance, however, is the restric-
tion of certain species to the Chicago region and to the southern portion
of the state. Among the ostracod species apparently found only in the
Chicago region may be listed Cypricercus tuberculatus, Notodromas
monacha, Cyprois marginata, Darwinula stevensom, and Limnocythere
verrucosa. Three of these, Cypricercus tuberculatus, Darwinula stev-
ensoni, and Limnocythere verrucosa are found only in the lakes of glacial
origin northwest of Chicago. Two species, Candona punctata and Cypria
mediana, appear to be confined to the southern part of the state.
MORPHOLOGY OF FRESH-WATER OSTRACODS
For a complete understanding of the relationships among groups and
species of the Ostracoda and in the use of the diagnostic keys, a working
knowledge of morphology is necessary. The descriptive morphology as
given here is offered not as a complete treatise on the subject but as an
aid in systematic work.
SHELL
The body of the fresh-water ostracod is completely enclosed by a
bivalve shell (fig. 96) from which no part of the body extends when the
shell is entirely closed. When the animal is active, however, the append-
ages used in swimming and creeping extend ventrally and anteriorly from
between the laterally placed valves (fig. 1). These valves are duplicatures
of the skin folds continuous dorsally with the body of the animal. Each
skin fold secretes shell material from both its surfaces, and the outer and
inner plates thus formed are fused together along the anterior, posterior,
and ventral margins of the shell. The outer plate is often more or less cal-
cified throughout its extent, but the calcified area of the inner plate is
limited to the marginal portion of the valve. The valves are often unequal
(figs. 96, 121), as either valve may overlap the other along certain por-
tions of the margin when the shell is closed. The nature of the overlap
is usually a useful specific characteristic. Anterior, ventral, posterior, and
dorsal margins are recognized. In some species of ostracods, the margin
of the valve along a part or all of its length may display tubercles (figs.
-116, 128), crenulations, or other structural markings. Often a hyaline
border extends beyond the margin and may form an extensive lip (fig.
118). Pore-canals (fig. 128-P) occur in many species as minute canals
lying between a submarginal line and the margin. When the submarginal
line and the margin are far separated, the pore-canals are long and con-
42 ILLINOIS BIOLOGICAL MONOGRAPHS
spicuous; when, however, the margin is approximate to the submarginal
line, the pore-canals may become obliterated.
The shell halves are connected along the dorsal margin by an elastic
band sometimes reinforced in the Cytheridae by a toothed, locking struc-
ture (fig. 137-AT, PT) which makes the closing of the valves more
certain. The halves are unconnected along the anterior, posterior, ventral,
and the fore- and hind-dorsal margins. The elastic hinge opens the shell
much after the manner in which opening of the shell is carried out in
bivalve molluscs. The closing of the shell is brought about by the con-
traction of a bundle of adductor muscles which extends from one valve to
the other, passing transversely through the body of the animal. The area
of attachment (figs. 40-M, 127-S) of the adductor muscles is conspicuous
on the valves of the shell. These muscle scars are located anterior to
the middle of each valve.
The nature of the surface of the valves often provides specific char-
acters useful in diagnosis. Variations occur in both surface sculpturing
and color. The shell surface may be smooth, pitted, or papillose. Setae
are commonly present along the valve margins and to a varying degree
on the shell surfaces. These setae may arise in connection with surface
sculpturing (fig. 103) or may occur independently of such markings
(fig. 118). In many instances, the color of the valve surface is so char-
acteristic that the species may be determined by skillful examination of
the color even in preserved material. In examining the shell for color,
both reflected and transmitted light should be used in order to detect
faint markings to the best advantage. In some instances, weak or faded
markings are revealed only after the shell has been cleared in glycerine.
Brown, green, or whitish gray are the prevailing colors. Color bands or
blotches are usually of a darker shade of green, brown, or black. Some
species exhibit a mother-of-pearl sheen when the valves are dried.
The size of the shell varies considerably in different species. The
minimum length of the mature shell in any species is about 0.25 mm.
while the maximum length of the shell is 21.0 mm. in a marine species of
the genus Gigantocypris (G. W. Miller 1912). Fresh-water forms seldom
exceed 3.0 mm. in shell length and in most cases are under 1.0 mm.
Bopy SEGMENTATION AND APPENDAGES
The shortened body of an ostracod shows externally no trace of
segmentation except as indicated by the metamerically arranged append-
ages (fig. 1). The boundary between the two body parts, the head and
thorax, however, is marked by a slight constriction; the abdomen is
wanting. The cephalic region bears four pairs of appendages: the
antennules, the antennae, the mandibles, and the maxillae. The thoracic
OSTRACODS OF ILLINOIS—HOFF 43
region has three pairs of appendages: the first, second, and third thoracic
legs. The body ends in a pair of furcal rami (except in Darwinulidae)
' homologous to the post-abdomen of the Cladocera. In the fresh-water
species, the appendages, including the antennae, are formed chiefly of the
endopodite as a result of the loss or reduction of the exopodite.
The two or three eyes (fig. 1-E), which are separated in the primitive
condition, are fused together to varying degrees. The eyes are usually
located in the dorsal part of the head anterior to the shell hinge and are
mounted on a low dorsal projection near the base of the antennules. The
eyes appear as a dorsal colored fleck when the shell is gaped. When the
shell is closed, the eyes may be seen as a pigment spot through the shell
in species having translucent valve lamellae. The eyes and the upper and
lower lips are not often mentioned in taxonomic work.
Anterior and dorsal to the mouth may be found the first cephalic
appendages, the antennules (fig. 1-AU) (often referred to as the first
antennae). The antennules are uniramous, the exopodite being lost.
Typically each antennule is composed of eight podomeres but through
fusion may approach a condition in which there are only five. The basal
portion or protopodite consists regularly of two podomeres which some
writers believe to be a single divided podomere (cf. Furtos 1933; Klie
1938a). In the Cypridae, the endopodite consists typically of five podo-
meres; in the fresh-water Cytheridae of North America it is reduced to
three or four podomeres. The antennules usually carry short, stiff, claw-
like bristles for digging and climbing (Darwinulidae and Cytheridae) or
long, feathered setae for swimming (fig. 1-N) (majority of the
Cypridae).
The second pair of cephalic appendages are the antennae (fig. 1-AN).
These are termed the second antennae when the antennules are desig-
nated as the first antennae. Each antenna includes a protopodite of one or
two podomeres and an endopodite of three or four podomeres. The
exopodite is reduced to a scale usually bearing three setae in the Cypridae,
to a long bent seta (fig. 131-F) containing the duct of a gland secreting
adhesive material in the Cytheridae, or is entirely vestigial in the
Darwinulidae. On the posterior margin of the first podomere of the
endopodite in the Cypridae is found a sensory organ (figs. 8-S, 106-O).
This same podomere often carries close to its distal end a group of five
long setae (fig. 1-V) which, when well developed, are used in swimming
by many of the Cypridae. These setae are greatly reduced in the
Cytheridae and the Darwinulidae, and are wanting in the Candoninae of
the Cypridae. Claws are found on the ultimate podomere of the endo-
podite. The antennae function in locomotion, in feeding, as a sensory
structure, and in the male as an organ for holding the female during
copulation.
44 ILLINOIS BIOLOGICAL MONOGRAPHS
The third pair of cephalic appendages are the mandibles located at
the sides of the mouth. Each mandible (figs. 1-M, 43) consists of a
base of two podomeres, a palp which represents the endopodite, and a
branchial plate (fig. 43-R) (sometimes reduced to a few setae) which is
modified from the exopodite. The basal portion is highly chitinized as
it is to this portion that the muscles used in operation of the mandibles
are attached. The distal end of the mandible is truncate and provided
with strongly chitinized teeth (fig. 43-C). The palp (fig. 1-P) consists of
the three podomeres of the endopodite and the second podomere of the
base. It bears claws and setae.
TEXT-FIGURE.—Mesial view of the left maxilla of Candona acuta sp. nov.
(female). I—inner masticatory process; M—middle masticatory process; O—outer
masticatory process; P—palp; R—respiratory plate. Scale: 0.2 mm.
The fourth pair of cephalic appendages are the maxillae, as shown
in the accompanying text-figure. These are the first maxillae of many of
the older authors, since this pair of structures is homologous with the
first maxillae of other crustaceans. The base of the maxilla has typically
three narrow distal masticatory processes and a palp of two or three
podomeres. The exopodite is well developed, forming a branchial plate.
The shape and number of setae on the masticatory process closest to the
palp are of considerable taxonomic importance. This process has been
variously called the masticatory process, the third masticatory process,
and the outer masticatory process. The last is preferred by the present
writer. In some Cytheridae, the palp and processes may be reduced.
The mandibles and the maxillae are the feeding structures, but the
first thoracic leg sometimes assumes a similar structure and function. The
mandibles not only break food into small particles but the palp helps in
sweeping food toward the mouth. The mandibles are supported in func-
tion by the maxillae whose processes push food toward the mouth, while
the branchial or respiratory plate not only removes excess and inappro-
priate food but also by its vibration creates a current of water for use in
respiration. In reference to the masticatory processes, both the English
term and its German equivalent (Kauladen) are misnomers, as the
processes do not chew the food but merely pass particles toward the
OSTRACODS OF ILLINOIS—HOFF 45
mouth. The second maxillae are wanting in the Ostracoda, but in the
older literature the term is sometimes applied to the first thoracic legs.
The thoracic portion of the body bears three pairs of appendages
(figs. 1-R, L, T) except in the males of the Cytheridae, which have a
pair of sensory structures (fig. 135) considered by some writers to be a
fourth pair of thoracic appendages. The nature of the legs is a useful
criterion for division of the fresh-water Podocopa into families. In the
Cytheridae the first, second, and third pairs of legs are similar in struc-
ture and are pediform; in the Darwinulidae, only the second and third
pairs are similar; and in the Cypridae, all the legs differ in structure.
_ The first thoracic leg (fig. 1-R) is often highly modified, and in the
Cypridae so resembles the maxilla that it is designated in the older
literature as the second maxilla. The first leg has at times also been
referred to as the maxillary foot or maxilliped because of its resemblance
to a “chewing foot” or jaw. In the Cypridae, the basal podomere or
protopodite ends in a masticatory process bearing setae (fig. 9). The
endopodite is modified as a palp often of a single podomere and the
exopodite forms a branchial plate which may be reduced to one or a few
setae as in the Cypridopsinae and Candoninae (fig. 9-R). The palp in
the male is often modified to form a prehensile claw (figs. 22, 71) of one
or two podomeres for use during copulation. When the prehensile palp
is formed of two podomeres, the proximal one is called the propodus
(fig. 122-P); the distal one is termed the dactylus (fig. 122-D). The
first leg in the Cytheridae is similar to the other two thoracic legs, since
it consists of an anteriorly directed protopodite carrying a pediform
endopodite of three or four podomeres. The exopodite or branchial plate
is wanting. In the Darwinulidae, the structure of the first leg is midway
between the condition found in the other two families, since the masti-
catory process as well as the branchial plate is well developed, as in many
Cypridae, and the endopodite is a pediform structure of three podomeres
similar to that of the Cytheridae.
The second thoracic legs (fig. 1-L) (first thoracic legs according to
those authors who recognize the here-designated first thoracic legs as
second maxillae or maxillipeds) are uniramous and consist of a pro-
topodite and a backwardly directed pediform endopodite at the end of
which is usually a more or less curved claw (fig. 26-C). The endopodite
consists usually of three or four podomeres, but in some species it may
appear to have an additional podomere through a division of the next
to the last podomere. The exopodite is lacking.
The third thoracic legs (fig. 1-T) (designated as second thoracic legs
by those authors who describe the first pair of legs as second maxillae or
maxillipeds) usually consist of five podomeres. The third leg is similar
46 ILLINOIS BIOLOGICAL MONOGRAPHS
to the second in the Cytheridae and the Darwinulidae, but in the Cypridae
it consists of a basal podomere and an endopodite typically of three
podomeres (fig. 4), of which one may be divided (fig. 53-P). In the
Cypridae, this leg is modified as a cleaning foot (German: ‘“Putzfuss’’)
by being bent dorsally and by being distally adapted for use in keeping
the shell and body free of foreign material. The modification consists
either of the presence of several unequal setae, usually three in number
and often reflexed in position, or a complicated pincer apparatus or chela
formed from the last two podomeres of the third leg (fig. 120) in the
Cyprinae s. str.
A possible fourth pair of thoracic appendages may be found in the
so-called “brush-like”’ organ (German: “biirstenformige Organ’’) (fig.
135) in the males of the Cytheridae. This appendage carries a tuft of
setae and is richly supplied with nerves. Its structure has led to the
assumption that it is a sexual sensory organ.
At the posterior end of the body in the Cypridae and the Cytheridae
there are paired appendages which are the remains of the abdomen.
When at rest, these furcal rami are directed ventrally between the third
legs. By being articulated with the body, they are capable of movement
and assist in locomotion. Typically, each appendage (fig. 69) consists of
a basal portion or ramus proximally articulated with the body and ending
distally in two setae and two claws. Various modifications may occur
in the Cypridae by the loss or reduction of one or more of the claws
or setae. The extreme degree of reduction in the Cypridae occurs in the
Cypridopsinae where each furcal ramus is reduced to a small base, a
dorsal seta, and a whip-like terminal part often referred to as the
“flagellum” (fig. 117). In the Cytheridae, the furcal rami are very much
reduced (figs. 132, 138); in the Darwinulidae, they are entirely wanting
and the thorax ends in a short cone-shaped process (fig. 126).
RESPIRATORY, CIRCULATORY, EXCRETORY, DIGESTIVE,
AND NERVOUS SYSTEMS
Respiration in the fresh-water ostracods is accomplished by gaseous
exchange through the entire surface of the body and especially through
the membranous inner lamella of the shell. Bernecker (1909) found the
inner shell lamella in Cyprinotus incongruens to be made up of seven
large respiratory cells which form a respiratory epithelium overlying the
valve cavity which constitutes a blood sinus. The renewal of water
within the shell cavity is accomplished by the movements of the
appendages. Thus the respiratory plates of some of the appendages not
only provide additional respiratory surface but also bring oxygenated
water into contact with other body surfaces.
OSTRACODS OF ILLINOIS—HOFF 47
Like the gills, the heart is also wanting in fresh-water ostracods,
although some marine species have a pulsating sac (Klie 1926a). Whether
or not there is any adaptation for circulating the body fluids in forms
lacking a heart is not known.
The excretory system in several species of European ostracods is
described in detail by Bergold (1910). There are three excretory organs:
the glands of the antennules, the shell glands, and the maxillary glands.
Each of the glands of the antennules is small and opens to the outside
ventral to the base of each antennule. The shell glands lie in the anterior
part of the shell between the lamellae, and their ducts lead to the outside
in the region of the second antennae. The third pair of glands are the
maxillary glands. Each of these consists of a coelomic sac and a urinary
duct, and one lies in the body at the base of each maxilla. By muscular
constriction, the excretion is forced from the sac into the looped canal
or duct.
Both Claus (1895) and Bergold (1910) discuss in detail the digestive
system. The alimentary canal consists of three parts: the ‘esophagus or
fore-gut, the mid-gut, and the hind-gut. The food material in the form
of minute organic particles is collected together in the atrium bounded
by the mouth parts. Here the particles are cemented together by secre-
tions from glands in the upper lip and in the base of the mandible near
the distal teeth. This food is passed down the esophagus into the anterior
portion of the mid-gut where the cells lining the tract are secretory and
also function in absorption of nutritive material. The largest digestive
gland is the paired hepato-pancreas or so-called liver which lies between
the shell lamellae and empties into the mid-gut. The straight and short
end-gut leads from the mid-gut to the anus which is located behind the
furca. Food balls may be seen in the mid-gut when the animal is examined
by transmitted light.
Good accounts of the nervous system in certain species of Cypridae
are given by Turner (1896) and Hanstrom (1924). The nervous system
in the fresh-water Cytheridae seems to have received no attention. In
general “the central nervous system consists of a supra-oesophageal
ganglion which is united to a ventral chain by a pharyngeal collar”
(Turner 1896). The supra-esophageal ganglion is made up of a large
number of fused ganglia, probably as many as seven (Turner 1896). The
anterior group of fused ganglia of the ventral chain is usually designated
as the infra-esophageal ganglion (Klie 1926a) and is made up of at
least three ganglia. The antennules and the antennae are innervated by
the supra-esophageal ganglion which is also connected to the optic ganglion
of the eye. The infra-esophageal ganglionic mass innervates the mouth
parts and the closing muscle of the shell. Posterior to the infra-esophageal
mass, there lie the two paired ganglia of the ventral chain. The first
48 ILLINOIS BIOLOGICAL MONOGRAPHS
innervates the first thoracic legs, the second gives off paired nerves to
the second and third thoracic legs and an unpaired nerve to the sexual
apparatus. While the ventral ganglia in the species examined by Turner
(1896) are well separated, Hanstrom (1924) found the infra-esophageal
ganglion and the visceral ganglia of the ventral chain to be fused closely
together in certain European species of Cypridae.
The sensory organs include the eye, tactile receptors, and chemo-
receptors. The eye usually consists of three optic systems more or less
fused together and is placed dorsal to the base of the antennules. The eye
is made up usually of three pigment cups, one median and two lateral
(Nowikoff 1908). Nowikoff, in working chiefly on European species of
the subfamily Cyprinae, found that each eye cup contains a number of
eye cells forming a concave retina. The number of cells in each lateral
cup is ten to fifteen, in the median one only seven or eight. The tactile
organs are in the form of setae scattered over the shell and body. There
are also well developed specialized tactile setae on many of the cephalic
appendages.
One very important sensory organ (fig. 8-S) is the one on the ante-
penultimate podomere or first podomere of the endopodite of the antennae
in the Cypridae. This has been considered an olfactory organ.
REPRODUCTIVE SYSTEM
The female sexual organs consist of paired ovaries, oviducts, seminal
receptacles, and genital openings. In the Cypridae the ovaries lie in the
space between the lamellae of each valve (figs. 18-O, 40-O) where in many
species they may be seen by transmitted light. In the Cytheridae the
ovaries lie lateral to the mid-gut in the body of the animal. Each oviduct
is joined near the outer end by the duct from the seminal receptacle. The
female genital openings lie between the third thoracic legs and the furcal
rami and may be at the end of distinctly well developed paired genital
lobes (figs. 30-G, 37-G) as in many of the Candoninae.
In the Cypridae, the testes lie in the cavity of the valves (figs. 21-T,
41-T), and each testis usually consists of four branches. The branches
unite to form the vas deferens of each side as they leave the valve cavity
dorsal to the muscle scars. The vas deferens makes several coils or loops
and then enters the dorsally and posteriorly located ductus ejaculatorius
or Zenker’s organ (figs. 93, 123) which by alternate contraction and ex-
pansion forces the sperms into the penis during copulation. The paired
copulatory organs are located posteriorly to the ejaculatory ducts and
serve to carry the sperm to the female. Each copulatory organ or penis
often has three lobes but some of these may be wanting (figs. 57, 72, 81).
Like the ovaries, the testes in the Cytheridae lie along the intestine
in the body proper. In members of this family there is no ductus ejacu-
OSTRACODS OF ILLINOIS—HOFF 49
latorius. The copulatory. organ consists of paired plates often with
several appendages (figs. 134, 141).
TAXONOMY
ORDER OSTRACODA
The Ostracoda, for which the common name “mussel-shrimps’’
(German: “Muschelkrebse’’) has been suggested by Johansen (1921),
include those crustacea which are enclosed by a dorsally hinged bivalve
shell and which never have more than four pairs of postoral appendages.
The ostracod shell bears some resemblance to the shells of certain Phyl-
lopoda (Conchostraca) but may be readily distinguished from the phyl-
lopod shell by the lack of growth lines. Furthermore, the Ostracoda may
be easily and certainly separated from the shelled Phyllopoda by the
specialized appendages of the former in contrast to the large number
(at least twenty) of foliaceous postoral appendages in the latter. On
superficial examination the shell of certain of the small bivalve molluscs
(as the Sphaeriidae) may also be mistaken for an ostracod shell by one
not familiar with the gross appearance of the forms. These may be
readily differentiated from ostracods by the presence of growth lines on
the shell and the lack of jointed appendages.
The order Ostracoda (with reference only to recent species) con-
tains about fifteen hundred valid species and perhaps nearly a thousand
additional species of uncertain status. Many ostracods are marine
but there are approximately five hundred recognized species from fresh
waters.
SUBORDERS OF THE ORDER OSTRACODA
The order Ostracoda may be divided into four suborders, based
chiefly on the nature of the shell, the number of postoral appendages,
and the character of the furca. The Ostracoda of fresh waters belong
entirely to the suborder Podocopa s. str., which also includes some marine
species. The other three suborders are strictly marine.
The suborder Podocopa s. str. may be characterized as follows: Shell
without a permanent aperture anteriorly. The antenna with the endopodite
well developed, but the exopodite, at the most, represented by a single
long seta (fig. 131-F) or small setae-bearing scale. Both antennules and
antennae are used in locomotion, either in swimming or creeping. The
mandibular palp consists of four podomeres (figs. 25, 43). The heart is
wanting; eyes are usually present. Four pairs of postoral appendages are
present. Caudal ramus, when well developed, rod-shaped (fig. 37-B) ;
often reduced (figs. 117, 132). Inhabitants of fresh and marine waters.
Over one-half of the known ostracods belong to this suborder.
50 ILLINOIS BIOLOGICAL MONOGRAPHS
For completeness and general information, some indication of the
characteristics of the three strictly marine suborders and a comparison
of their structure with the suborder Podocopa is given here:
(a) The suborder Myodocopa s. str. is characterized by having at the
anterior end of the shell a permanent opening through which the antennae
may be extended for use in locomotion when the shell is otherwise tightly
closed. The antennules are not highly developed for swimming. There
are four pairs of postoral appendages, and the furca is lamelliform. A
heart is present. The suborder Podocopa s. str. may be separated from the
suborder Myodocopa s. str. by a lack of a permanent anterior shell open-
ing, the absence of a heart, and the presence of a bar-like rather than
a lamelliform furca.
(b) The suborder Cladocopa may be separated from the suborder
Podocopa s. str. by the presence in the former of only two pairs of
postoral appendages and by having the body terminate in reflexed lamelli-
form processes bearing numerous spines. The heart and eyes are absent
in the suborder Cladocopa.
(c) The suborder Platycopa is characterized by biramous antennae,
both branches being well developed with broad flattened podomeres. There
are three pairs of postoral appendages, none of them distinctly leg-like.
The furcal ramus is leaf-like, widened distally, and the margin bears many
spines. The eye and heart are wanting. The subfamily Podocopa s. str.
may be separated from the Platycopa by the presence in the former of
four pairs of postoral appendages, usually well developed eyes, poorly
developed exopodite of the antenna, and the bar-like furcal ramus.
While Sars (1928) and Klie (1938a) follow the division of the order
Ostracoda into four suborders as given herein, G. W. Miller (1912, 1927)
follows a different scheme and divides the order Ostracoda into two sub-
orders: Myodocopa and Podocopa. The first suborder embodies the
Myodocopa s. str. and Cladocopa as used herein; and the second combines
the Platycopa and the Podocopa s. str. as recognized by the present writer.
The system in which the order Ostracoda is divided into two suborders
rather than four is certainly not a natural classification and is therefore
to be avoided. Skogsberg (1920) recognizes five suborders, the additional
group being formed by a division of the Myodocopa. Since the Myodo-
copa are entirely marine, no discussion need be given here of Skogsberg’s
classification.
FAMILIES OF THE SUBORDER PODOCOPA. si,
The suborder Podocopa s. str. includes four families, three of which
are found in fresh waters. If the suborder Podocopa is considered in the
broad sense (as by G. W. Miller, 1912, 1927), then a fifth family, the
family Cytherellidae, must be added to include the single marine genus
OSTRACODS OF ILLINOIS—HOFF 51
Cytherella. Cytherella, however, has many characteristics which are above
the rank of family criteria and so is properly placed by itself in the sub-
order Platycopa.
The four families recognized herein as belonging to the suborder
Podocopa s. str. are the families Cypridae, Darwinulidae, Cytheridae, and
Nesideidea.* Of these, the family Nesideidae is strictly marine, Dar-
winulidae is entirely fresh-water, Cytheridae is chiefly marine with a few
fresh-water genera, and Cypridae is common in both marine and fresh
water. The following tabulation shows the chief structural differences
among the four families of the suborder Podocopa s. str.
Teeth of Exopodite of Furcal
Family shell hinge antenna Thoracic legs ramus
SEPIA AG a elie aie cys see eres + None Reduced to a All different Usually well
- small scale developed
bearing setae
Darwinulidae........... None Greatly Second and Wanting
reduced third similar
OS GS CET Ei . Present or Large seta All similar Reduced
vestigial forming a
gland duct
Nesideidae............. None Small scale All similar Well devel-
bearing a oped
few setae
KEY TO FAMILIES OF THE SUBORDER PODOCOPA IN ILLINOIS
la. Exopodite of the antenna in the form of a long hollow seta carrying the
secretion from a gland near the base of the antenna (fig. 131-F) ; the thor-
UE REE EAN Eas faeces ng Series a She hres pete hoot oe Family CyTHERIDAE
b. Exopodite of the antenna not as in the family Cytheridae; the thoracic legs
MeN NREL AS ee NIG 2's SASS Ticats Gly ach koa 8 SORES wp boone Nat Ciae mune TO ee ie See BU als z
2a. Second and third thoracic legs similar in structure and direction; furca
EE RR SSF ae a fe Family DARWINULIDAE
b. Second and third thoracic legs differ in structure and the direction of ex-
tension (fig. 1-L, T) ; furca present but sometimes much reduced..........
PDC OSE 0.0 OUD DEA. SOOO BRIO ERO REET TIER ebro anaes ena s mere Family CyPprIDAE
FAMILY CYPRIDAE
Surface of the shell usually smooth; dorsal margin without inter-
locking teeth. Eyes developed to varying degrees; either separated or
fused into a single median eye. The antennules with a basal portion of
two or three podomeres and an endopodite of four or five podomeres,
with swimming setae well developed. The antenna with a basal part of
*The family Nesideidae should perhaps be replaced by Bairdiidae since the two names appear
to be synonyms, at least by virtue of their having synonymous type genera, Bairdia M’Coy 1844
being recognized as synonymous with Nesidea Costa 1847. The genus Bairdia and the family
Bairdiidae have long been accepted by geologists in reference to fossils. The genus Nesidea and
the family Nesideidae have, on the other hand, been used extensively by zoologists working on
recent material. Sars (1928) approves the use of Bairdia rather than Nesidea for recent species
and this practice should perhaps be followed.
aj. OF ILL. LIB.
52 ILLINOIS BIOLOGICAL MONOGRAPHS
two podomeres and an endopodite of three or four podomeres. The
exopodite is reduced to a small scale-like appendage bearing at the most
three setae. First thoracic leg not pediform but modified as a mouth part,
with the anterior margin of the base adapted for feeding. The endopodite
of the first leg forms a small palp in the female but is enlarged to form
prehensile organs in the male (figs. 63, 122). The second thoracic leg
has an endopodite of three or four podomeres and a strong distal claw
(fig. 26). The third leg is bent dorsally and is probably used in cleaning
the respiratory surfaces and other parts of the body. The third leg usually
has three distal setae (fig. 27) but the distal end may be modified for
grasping (fig. 120). The furca is typically well developed and rod-shaped
(fig. 11) but may be reduced to a “flagellum” or whip-like structure —
(fig. 117) (Cypridopsinae). The gonads are located within the valves
of the shell. In the male, a portion of the vas deferens is modified to
form an ejaculatory duct (fig. 93). The family Cypridae is large and
includes the majority of fresh-water ostracods.
Since the family Cypridae is so large, it has been convenient to sub-
divide it into several subfamilies. Two well recognized subfamilies,
Pontocyprinae and Macrocyprinae, are strictly marine and merit no
further consideration here. Fresh-water representatives of this family
have been systematized into a varying number of subfamilies. G. W.
Miller (1912, 1927) recognizes, in addition to the two marine subfamilies
mentioned, only three subfamilies in the Cypridae; the subfamily Can-
doninae (Candocyprinae of some authors), the subfamily Ilyocyprinae,
and the subfamily Cyprinae. Two of these subfamilies are conglomera-
tions of genera with greatly diversified characterization and as a result the
groupings are distinctly unnatural. In order to form natural groupings,
as far as the subfamilies are concerned, it is necessary to split the Can-
doninae and the Cyprinae into smaller groups, each representing a single
genus or a group of closely related genera. Kaufmann as early as 1900
(1900b) divided the family Cypridae into eight subfamilies. His system
is usable with a few minor corrections in orthography and a combination
of his subfamilies Herpetocypridinae and Cypridinae into the subfamily
Cyprinae s. str. The fresh-water subfamilies of the family Cypridae may
be listed as follows, with the two recognized schemes in parallel columns:
Subfamiltes according to Subfamilies after Kaufmann (19006) ;
G. W. Miiller (1912, 1927) used by Wagler (1937) and
and Klie (1938a) the present writer
: . Candoninae s. str.
Candoeninae (Candocyprinae): sce sie ae ees \odonaaee
Tlyocyprimae jcc stee. ct ours oer < cerea ake eve meen teeter ee Borer Ilyocyprinae
Cyprinae s. str.
|Cspropsina
Notodrominae
Gy prinde aie coins oes cetera ot Wee Cio LA eke Gemeiesaemeronete
OSTRACODS OF ILLINOIS—HOFF
rt
3
All the subfamilies listed to the right are strictly fresh-water inhabitants
except the subfamily Cyclocyprinae which has, in addition to several
genera found in fresh water, a single genus which is marine.
KEY TO SUBFAMILIES OF THE FAMILY CYPRIDAE
FOUND IN FRESH WATERS
la. Furcal rami greatly reduced, whip-shaped, without a terminal claw at the
end (dificult to observe) (fig. 117)..........000000.. Subfamily CypripoPsINAE
b. Furcal ramus well developed, bar-shaped, with two terminal or subterminal
eR ND) Py oy ya ya ooo a css die aru es RES EO aT at Oe el cok value, 6 Seuste hs 2
2a. Outer masticatory process of the maxilla with six nearly equal setae modi-
gente erorm: toothed spines (fig. 113)................ Subfamily NoTopRoMINAE
b. Outer masticatory process with two or three of the setae modified as spines...3
3a. Swimming setae of the antenna completely wanting (fig. 8)...............
- 0-220 ot SAE ERR ee ene ea era Subfamily CANDONINAE s. str.
b. Swimming setae of the antenna present (fig. 1-AN, V)............ cece eeeee 4
4a. Third thoracic leg distally modified as a seizing apparatus, the ultimate
podomere being beak-like with two well developed bristle-like setae, the
third seta wanting or hook-like (fig. 120).......... Subfamily Cyprinae s. str.
b. Third thoracic leg not bearing a chela, last podomere cylindrical and bear-
ape EMS ELC (CIES) 591 079!) Sera cecesarakcvace, sel dia’w-e aisle Ba w HGS Bee ete atthe Meee: 5
5a. Shell elliptical to subrectangular (fig. 99), swimming setae of the antenna
do not extend much beyond the tips of the end claws; palp (endopodite)
of the first thoracic leg small, pediform, of two or three podomeres........
a eco athe asa hd Oras isle a glee a brad uw e ee eels Subfamily ILyocyprRINAE
b. Shell usually short and rounded (fig. 73), at least not subrectangular;
swimming setae of the antenna extend well beyond the terminal claws (in
Illinois species) ; the palp of the first thoracic leg of one or two podomeres
in the female, always two in the male; not pediform. .Subfamily CycLocyPrINAE
SUBFAMILY CANDONINAE s. str.
Shell white, porcelain-like, often with mother-of-pearl sheen when dry.
Swimming setae of the antennae absent (fig. 8). Two special sensory
setae are usually located at the juncture of the fourth and fifth podomeres
of the male antenna. Respiratory plate (exopodite) of the first thoracic
leg with two or three setae (fig. 9-R); palp (endopodite) in male and
female unjointed. Third thoracic leg with three unequally long setae on
the last podomere (fig. 4), the penultimate (third) podomere either di-
vided (fig. 53-P) or undivided (fig. 10-P). If divided, the third leg has
five apparent podomeres. Ejaculatory apparatus of the male usually with
seven wreaths of chitinous spines; openings of the ejaculatory duct
funnel-shaped.
The Candoninae are creeping and burrowing forms as indicated by
the lack of swimming setae on the antennae. The members of this group
54 ILLINOIS BIOLOGICAL MONOGRAPHS
are found in a variety of habitats and are widely distributed. Many
species, however, are taken sparsely because they are often limited sea-
sonally and do not occur in great abundance.
The subfamily Candoninae contains, according to some authors, as
many as five genera. Of these five genera, two, Candona and Paracandona,
are found in North America. The genus Candona alone has been found
in Illinois. Almost without exception, the Candoninae are restricted to the
Holarctic Region.
Genus CANDONA Barrp 1845
Valves of the shell white, sometimes transparent; may have a mother- .
of-pearl sheen; surface smooth, sometimes with scattered puncta and
hairs; hairy in some species. Shell variable in shape and size, elongated
ovoid to reniform (fig. 50), sometimes with a straightened dorsal margin
and truncated ends (fig. 65). Swimming setae of the antennae absent
(fig. 8); the antennae of five podomeres in the female, often of six
apparent podomeres in the male through a division of the penultimate ;
two male setae often present at the juncture of the two divisions. The
last two podomeres of the mandibular palp short, rounded (fig. 43).
Respiratory plate of the first thoracic leg rudimentary, usually with two
unequal setae, never more than three (fig. 9-R). The third thoracic leg
commonly of four podomeres; sometimes appearing to consist of five
podomeres through a division of the third or penultimate podomere (fig.
53-P). When such a division occurs, there is no seta at the juncture of
the two divisions. The terminal podomere of the third thoracic leg is
short and bears two backwardly directed setae (fig. 4-C) and one long
forwardly directed seta. The furcal ramus (fig. 11) is strong, bearing
two strong claws and one or two setae; the dorsal seta often being
removed from the subterminal claw by about twice the least width of the
ramus. Male sexual organs with the characteristics of the subfamily. |
Fifteen species of the genus Candona have been found in Illinois. Of
these, six are described herein as new species. Of the six species of
Candona reported for Illinois by Sharpe (1897), the present writer has
rediscovered and added to the description of two, has redescribed one as
a new species on the basis of additional material which showed that it
is not the European species to which it was assigned by Sharpe, and has
found one to be a synonym. Two of Sharpe’s reported species were not
found in the present writer’s collections. One of these two, however, was
assigned a new name because the individuals as described obviously do
not belong to the species to which they were assigned by Sharpe.
The genus Candona is a very large one, over one hundred and fifty
OSTRACODS OF ILLINOIS—HOFF 55
species being reported in the literature. A lack of understanding of the
relationships among species has resulted in the genus as a group becom-
ing taxonomically unwieldy. Following a failure to divide the genus
Candona by placing some of the species in new genera, various attempts
have been made to divide the genus into groups. The groups suggested are
of less than sub-generic value and each group is based on a type species.
As early as 1900, G. W. Miiller divided the genus as found in Germany
into three groups. A discussion of this and later groupings may be found
in Furtos (1933). The present writer has followed the system given by
Klie (1938a) who has greatly modified the earlier scheme. According to
Klie, there are seven groups in the genus Candona: groups Candida,
Rostrata, Fabaeformis, Compressa, Acuminata, Cryptocandona, and
Mixta. A key to these groups based on the work of Klie is given herewith.
KEY TO GROUPS OF THE GENUS CANDONA
la. The branchial plate of the first thoracic appendage has two setae (fig. 9-R)...2
Beene branchial plate has: three .setae..:...-cs0sdss0ecedarescegccgssovsmecias 6
2a. The medial seta on the distal margin of the next to the last podomere of
Genrandipular palp feathered. ). 4. 53.4... uesocsateeussseeae Group CANDIDA
Meee apove-mentioned seta wnieathered=..20..:...4.05<eeecslcecckh meneasess 3
3a. Sexual lobe of the female mostly rounded (fig. 11-G); when pointed, then
short and not prolonged lappet-like toward the posterior (fig. 15-G). Shell
rounded; typically but not necessarily, the height is greater than one-half
SE MRAZ Sy ck Sites spate Gare aoe ess dee APS LUNs Son eke ROR ft 4
b. Sexual lobe of the female pointed and prolonged lappet-like toward the
posterior (fig. 69-G). Shell typically elongated, height usually but not
mays tess than one-half the length (fig. 58) 2:0... 0... 5050000cssineivecise’es 5
4a. Three setae in the bundle on the inner margin of the antepenultimate
Honogere of the mandibular palp: .o. 7... 066. ec eeeve ceeccues Group RostRATA
b. More than three setae in the bundle (fig. 25-B).............. Group CoMPRESSA
5a. Either three or five setae in the bundle on the inner margin of the ante-
penultimate podomere of the mandibular palp.............. Group FABAEFORMIS
beweur setae in the bundle (fic. 43-S). 0. ...<6cceasda00ccactan Group ACUMINATA
6a. A seta is present in the middle of the penultimate podomere of the third
SMR ERDME NSO Pa re ers! hare Lleccislé S Fash nicks si ee Group CRYPTOCANDONA
fermeriucniioned seta lacking. os c.<..cces ase ccwegs aa seeadnsde see Group MIxTa
All seven groups of the Candona may be found in North America
with the exception of the groups Cryptocandona and Mixta. It is im-
possible, because specific descriptions are incomplete, to assign some of the
American forms definitely to the proper group. Moreover, there is some
confusion in regard to many American forms because, as the groups are
built around European type-species, American species do not always fit
perfectly into this apparently artificial scheme.
56
ILLINOIS BIOLOGICAL MONOGRAPHS
The possible group assignments of species occurring in Illinois are as
follows:
Group Rostrata Group Acuminata
C. simpsoni Sharpe 1897 C. crogmaniana Turner 1894
C. punctata Furtos 1933 C. sigmoides Sharpe 1897
C. fluviatilis sp. nov. C. recticauda Sharpe 1897
(probable assignment)
Goep ompneess C. sharper sp. nov.
C. albicans Brady 1864 (questionable assignment)
C. biangulata sp. nov. © caudate Kantaanloun
Group Fabaeformis C distincta Furtos 1933
C. sharpei sp. nov. (very C. indigena sp. nov.
questionable assignment) C. suburbana sp. nov.
C. acuta sp. nov.
C. fossulensis sp. nov.
KEY TO SPECIES OF THE GENUS CANDONA IN ILLINOIS
(Based on characters available in the female)
. Penultimate podomere of the third thoracic leg undivided (fig. 10-P)........ 2
. Penultimate podomere of the third thoracic leg divided (leg of five appar-
ent podomeres). (fig: 53-P)cccisc dei. dese. ceeee cee oh te oe 4
. Shell with high rounded arch dorsally; height more than one-half the
Te tcthn trey 2) co seleaecatie ar Poitectetelevarete, sua aera el Gates C. punctata Furtos 1933
. Shell lacking a high rounded arch dorsally; height equal to or slightly less
than: one-half the lengthy... <0. fice G 0 eed Ye sete oe calsle pee 3
. Dorsal margin of the shell flattened and horizontal (fig. 6)..............
sonra te AN Beer oe Reve ty eso he Os RGR Be BURR ors. aN as A Paved ce ere C. fluviatilis sp. nov.
. Dorsal margin of shell forms a low evenly rounded arch (fig. 12)........
ROSE RI adays: BUSS CSCO. Meme Ack ceo eee itt See hee tg ee Rane C. simpson Sharpe 1897
. Shell of female less than 0.90 mm. in length...................... 02-0 eee eees 5
» Shell greater than 0:90 mm. in length... ..0. 2.00 ose eo eee 6
. Shell with a conspicuous dorsal-anterior sinuation; anterior end narrowly
rounded (fig. 24). Genital lobe of female conspicuous but small, cone-
Shapedin (ee s2o- er hota kaedon eee trae cya atone name Sate a et ata C. biangulata sp. nov.
. Shell without dorsal-anterior sinuation; anterior end broadly rounded (fig.
18). Genital lobe of female weakly developed, inconspicuous..............
eR UP Brena Ac tin Gist MRA cen tyrone NT acithe: ono etO IG GOS C. albicans Brady 1864
. Length of ventral margin of furcal ramus not over seven times the least
Widthuol the matmSi oa icsc cmc ee oc cule clon ole seater steerer erations C. sharpet sp. nov.
. Ventral margin of ramus at least eight times the least width of the ramus....7
. Length of dorsal seta of furca more than four times the least width of the
ramus and longer than the subterminal claw...... C. crogmaniana Turner 1894
. Length of dorsal seta four times or less than four times the least width of
the ramus and shorter than the subterminal claw...............2+-.eeeeeeees 8
. The terminal claw and more especially the subterminal claw of the furca
weakly but distinctly S-shaped (fig. 37-C, T)........ C. sigmoides Sharpe 1897
. The terminal and subterminal claws gently curved, not S-shaped............ 9
OSTRACODS OF ILLINOIS—HOFF 57
9a. In the third thoracic leg, the shortest seta has a length of over three times
that of the ultimate podomere; the companion seta is about equal to or less
than twice the length of the shortest distal seta (fig. 53)...............0005. 10
b. In the third thoracic leg, the shortest distal seta has a length not over three
times that of the ultimate podomere; the companion seta is over twice as
Bereecetne snorer of the pair. (fig. 45) 2400 igh so aetee cs ae dine eos due vs 14
10a. Shell rather elongate with the dorsal margin evenly arched; prominent
posterior ventral angulation especially in the left valve (fig. 33)..........
PMT Oe eens oan Ste Sine natds Paes hee temecm esse C. caudata Kaufmann 1900
b. Shell with dorsal margin forming an angulation or sinuation or both
(iyge, GADD) a cg 6 ine eg ey Se Ae eo A eR ee 11
lla. Shell height less than one-half the length. Female genital lobe a short
sane (Cie, GEE Cy ee eee en Onno eee isin carta mmf C. suburbana sp. nov.
b. Shell height equal to or greater than one-half of the length. Female
Cento Opemwelly- developed!) oj cian. vei eco Posse tia voristl ver aera eee ae.s sccee hols IZ
12a. Tip of female genital lobe unevenly bifurcated (fig. 30-G). Posterior end
of shell evenly rounded; prominent posterior-dorsal sinuation (fig. 29)
PPI Try cos clisyed car's spevereve Sioua seus io eva wreteyas ere etade edenecameelareners C. distincta Furtos 1933
b. Tip of genital lobe pointed. Posterior end of shell not evenly rounded,
subtruncate; posterior-dorsal sinuation lacking or shallow................ 13
13a. Female genital lobe lappet-like and separated from the thorax (fig. 69-G).
Shell without markings on the posterior slope; prominent posterior-ventral
sincqollarskern. (Giese OS) A aera gery genes GBS Gen Gn Saadeh doo odes omc C. acuta sp. nov.
b. Female genital lobe finger-like, not separated from the thorax (fig. 62).
Sculpturing on posterior slope of female shell (fig. 59); juncture of pos-
terior and ventral margin of shell rounded (fig. 58)....C. fossulensis sp. nov.
14a. In the second thoracic leg, antepenultimate podomere at least equal to the
penultimate (fig. 44). Companion seta of third thoracic leg equals two and
one-half times the shorter of the pair (fig. 45)........... C. indigena sp. nov.
b. The second thoracic leg with the antepenultimate podomere equal in length
to two-thirds of the length of the penultimate podomere. Companion seta
of the third leg has a length equal to three and one-half times the shorter
GLE (HS SOE Rea I aeirer ies ey ange ae, eR ea a C. recticauda Sharpe 1897
Group Rostrata
Shell may be beset with many long hairs; shell often moderately short
and high so that in most species the height exceeds one-half the length.
The respiratory plate of the first thoracic leg is reduced to two setae
(fig. 9-R). The mandibular palp has the medial seta on the distal margin
of the penultimate podomere smooth, and the bundle on the antepen-
ultimate podomere consists of three setae. Genital lobe of the female
reduced and usually rounded (figs. 5-G, 11-G); if pointed, then short
and not projected much posteriorly (fig. 15-G). Penis usually short and
wide with the lobes flap-like and lying one over another. Three species of
Candona, C. simpsoni Sharpe 1897, C. punctata Furtos 1933, and C. fluvi-
atilis sp. nov. have been placed in this group.
58 ILLINOIS BIOLOGICAL MONOGRAPHS
KEY TO SPECIES OF THE GROUP ROSTRATA IN ILLINOIS
la. Shell height considerably more than one-half the length; the length of the
ventral margin of the furca over nine times the least width (fig. 5)........
Fie aa aie Pie nit oy ei ge OR EN R En RE MLA a Au8 FS OA ge i C. punctata Furtos 1933
b. Shell height equal to or less than one-half the length; the length of the
ventral margin of the furca less than nine times the least width (fig. 11)....2
2a. Dorsal margin of shell straight and horizontal (fig. 6); surface of shell
SCUMpLURed (Mey) itt state sPeraters Solace ae une nie onc ene ene C. fluviatilis sp. nov.
b. Dorsal margin of shell evenly arched (fig. 12). Shell elliptical; surface of
SHellesmrOothe kaif eee Aaron one eo Meee eae C. simpsoni Sharpe 1897
Candona punctata Furtos 1933
CPI, dy tie 2-5)
Candona punctata Furtos 1933. Furtos, 1933:485-486, pl. 13, figs. 2-8.
Type Locality: Ohio.
Description of the Female: A Candona of the Rostrata group. The
shell (fig. 2) is much higher than one-half of the length; ventral margin
nearly straight with but very slight sinuation; dorsal margin convex and
passing into the posterior margin without an interruption in the arc.
There is a shallow sinuation between the dorsal and the anterior margins.
The anterior margin is more narrowly rounded than the posterior. A
view from above was not obtained in the Illinois material but observations
of single valves mounted in diaphane indicate a width of about four-
fifths the height with sides centrally bulged and narrowed anteriorly and
posteriorly, giving the animal, according to Furtos (1933), a spindle-form
appearance. The left valve is slightly larger than the right. The valves
have numerous long, heavy hairs which come from weakly developed
papillae. The hairs are conspicuous along the anterior and posterior
margins. The surfaces of the valves are areolated making accurate de-
termination of the muscle scars hazardous. The muscle scars, however,
appear to be five in number, arranged in a rosette, and are located sub-
centrally. The pore-canals are obliterated. A weak hyaline border is
conspicuous beyond the margin proper. The dimensions of the valves
of the single mature Illinois female are as follows (mounted in diaphane) :
RIGHT LEFT
Length Height Length Height
0.80 mm. 0.45 mm. 0.83 mm. 0.46 mm.
According to Furtos (1933), the length of the female is 0.85 to 0.90 mm.,
the height 0.45 to 0.51 mm., and the width 0.37 to 0.42 mm. These
measurements exceed slightly the size of the individual from Illinois.
The second podomere of the antennule bears a pair of setae, the longer
of which reaches to the seventh or eighth podomere, the shorter only to
the fifth or sixth podomere. The third and fourth podomeres of the
OSTRACODS OF ILLINOIS—HOFF 59
antennule are little longer than wide; the penultimate and ultimate
podomeres are equal in length, the ultimate being about seven times as
long as wide. The penultimate podomere of the antenna has on the inner
edge a very short spine at the distal end of the basal one-third and a long
seta at the beginning of the distal one-third. This seta reaches almost
to the tip of the shortest distal claw of the appendage. The mandibular
palp has the medial seta of the penultimate podomere unfeathered and
three setae in the bundle on the antepenultimate podomere. The two
longest claws of the ultimate podomere of the palp are nearly equal in
length and shape. The branchial plate of the maxilla has sixteen rays.
The second thoracic leg (fig. 3) is composed of five podomeres, the
second of which is equal to or slightly less in length than the sum of
the third, fourth, and fifth podomeres taken together. The medial distal
seta of the second podomere is equal in length to the width of the third
podomere. The third or antepenultimate podomere is about twice as long
as wide and has a seta about equal to or slightly larger than the width
of the penultimate podomere. The penultimate podomere is not quite
as long as the next proximally situated one but is of the same general
shape. The ultimate podomere is much longer than wide. The terminal
claw (fig. 3-E) is equal to one and one-third times the sum of the lengths
of the three distal podomeres. The third thoracic leg (fig. 4) has the pe-
nultimate podomere (fig. 4-P) undivided. The basal podomere has three
setae. Third podomere (penultimate) about equal in length to the second
and bears a seta which is hardly half as long as the length of the podo-
mere. The ultimate podomere is square; the length of the shortest distal
seta is three times the length of the ultimate podomere. The length of the
longer companion seta is two and one-quarter to two and one-half times
the length of the shorter (fig. 4-C). The oppositely directed seta is about
three and one-fourth times as long as the shorter seta of the pair.
The furca (fig. 5) has a nearly straight ventral margin; the dorsal
margin is slightly concave. The length of the ventral margin is ten times
the least width of the ramus; the terminal claw is two-thirds as long as
the ventral margin. The dorsal seta (fig. 5-D) is nearly two and one-half
times as long as the least width of the ramus, and is located a distance
of nearly twice the least width of the ramus from the subterminal claw.
The length of the terminal seta is less than the least width of the ramus.
The claws are long, slender, and gently curved with some indication of
being fine-toothed. The female lobe is undeveloped (fig. 5-G)..
Description of the Male: The present writer has observed no males
of this species. According to Furtos (1933), the males reach a length of
0.93 mm. and the shape of the shell is very similar to that of the female.
Remarks: Most of the above description has been taken from a single
60 ILLINOIS BIOLOGICAL MONOGRAPHS
Illinois specimen. The description agrees definitely with that given by
Furtos. Through the present writer’s description, it is evident that this
species belongs to the Rostrata group. Because of the uncertainty of the
taxonomic importance which may be attached to different structures, it
is not advisable at the present time to point out relationships beween
C. punctata and related European species.
Ecology: Furtos (1933) reports C. punctata to be “common in
temporary and permanent ponds, marshes and lakes. March to May,
and November.” A single mature female was found by the present writer
in a collection made from a swampy pool on March 26, 1939; an imma-
ture female was collected from a shady pool in an old stream bed on
June 6, 1940.
Distribution: . This species was originally reported from several
localities in Ohio by Furtos (1933). The present writer found a single
mature female in a collection of crustacea from Indian Creek Valley
near Carbondale, Jackson Co., Illinois. This collection was made by Mr.
F. R. Cagle of the Southern Illinois State Teachers’ College and sent to
Dr. Victor Sprague from whom the writer obtained the material. An
immature individual was obtained in a collection from Hardin County,
Illinois.
Candona fluviatilis sp. nov.
(Pl. I, figs. 6-9; pl. II, figs. 10-11)
Type Locality: Illinois.
Description of the Female: A Candona of the Rostrata group. The
shell is somewhat compressed; the width is less than the height. The
valves (fig. 6) of sexually mature females range in length from 0.68 mm.
to 0.76 mm. and in height from 0.33 mm. to 0.38 mm., the length being
approximate to twice the height. The dorsal margin of the shell is straight,
nearly horizontal; the anterior end is evenly rounded, a sinuation occur-
ring between the anterior and the dorsal margins. The posterior end is
rather blunt with a flattened margin. The ventral margin is centrally
somewhat concave. The ovary is slender; the muscle scars (fig. 7-M) are
subcentrally located and consist of a rosette of five scars with a single
slightly more dorsally located scar and often another scar anterior to the
group. The submarginal line is so close to the valve margin that the
pore-canals are practically obliterated anteriorly and posteriorly. The
shell is conspicuously sculptured (fig. 7-S), being entirely covered by
areolations formed of pits separated by raised areas. Many very fine,
short hairs are found on the surface and margins of the shell.
The antennules present few specific characters; the third and fourth
podomeres are as wide as long, the fourth appears fused to the fifth; the
fifth, sixth, and seventh podomeres are stouter and shorter than in many
OSTRACODS OF ILLINOIS—HOFF 61
Candona; the distal podomere is three times as long as wide. The sensory
organ (fig. 8-S) of the penultimate podomere of the antenna reaches to
the distal margin of the podomere. The ultimate podomere is about one
and one-half times as wide as long; the longest claws of the penultimate
and ultimate podomeres are as long as the sum of the lengths of the
distal three podomeres of the appendage. The teeth of the mandible are
long and finger-like, few in number. The medial-distal seta of the penulti-
mate podomere of the palp is smooth; there are three setae in the bundle
on the antepenultimate podomere of the mandibular palp. The branchial
plate of the maxilla has twenty-three rays, five of which are directed
orally. Details of the first thoracic leg are shown in the figure (fig. 9).
The second thoracic leg has the distal setae of the second, third, and
fourth podomeres approximately equal to the distal width of the respective
podomere. The ultimate podomere is longer than wide and bears, in
addition to the long claw, two setae, the shorter of which is about as
long as the width of the distal end of the podomere, the other approxi-
mately equal in length to the proximal margin of the podomere. The
length of the terminal claw of the second leg is one and one-third times
the sum of the lengths of the three distal podomeres.
The basal podomere of the third thoracic leg (fig. 10) has three setae;
the penultimate podomere (fig. 10-P) is undivided. The ultimate podo-
mere is at least as wide as long; the short seta measures two and one-
half to three times the length of the podomere, the companion one is two
and one-fourth to two and one-half times as long as the short seta, and
the oppositely directed one is but little longer, if any, than the other long
seta. The seta of the penultimate podomere is seven-eighths as long as
the podomere. The furcal ramus (fig. 11) is rather stout and little curved,
the length of the ventral margin is approximately six times the least
width; the dorsal seta is subequal to twice the least width of the ramus
and is located from the subterminal claw a distance equal to the least
width of the ramus. The claws are slender, gently curved, and nearly
equal in length; the terminal one has a length equal to six-sevenths of
the ventral margin of the ramus. The teeth of the claws are so fine
that superficially they appear smooth. The length of the terminal seta
is approximately equal to one-half of the least width of the ramus. The
female genital lobes (fig. 11-G) form large, well rounded semicircular
flaps which extend posterior to the furcal rami when the furca is flexed.
No seta is found on the thorax dorsad to the furca.
Male: The male is unknown.
Remarks: The combination of characters found in this species makes
comparison with other species of the group Rostrata more or less worth-
less until more information is available regarding the details of anatomy
of the American forms.
62 ILLINOIS BIOLOGICAL MONOGRAPHS
Ecology: C. fluviatilis has been taken in only three collections, all
of which were from small vernal streams not over three feet wide and
ten inches deep, with clear, gently flowing water usually over a muddy
bottom.
Distribution: Several mature individuals of C. fluviatilis sp. nov. were
taken on June 20, 1940, near Roberts, Ford County; a single individual
was taken on May 18, 1940, near Savoy, Champaign County; and three
very immature specimens were collected near Henry, Marshall County,
Illinois on May 30, 1940.
Cotypes are deposited in the U. S. National Museum (Cat. No. 81066),
in the collection of Dr. H. J. Van Cleave, and in the writer’s collection.
Candona simpsoni Sharpe 1897
(Pl. II, figs. 12-17)
Candona simpsoni Sharpe 1897. Sharpe, 1897:452-454, pl. 46, figs. 1-6; Kofoid,
1908 :258.
Candona reflexa Sharpe 1897. Sharpe, 1897:457, pl. 47, figs. 1-3; Kofoid, 1908:258.
Candona exilis Furtos 1933. Furtos, 1933:483, pl. 12, figs. 14-17.
Type Locahty: (C. simpsont) Illinois; (C. reflexa) Havana, Illinois ;
(C. exits) (Ohio.
Description of the Female: A Candona assignable to the Rostrata
group. The shell (fig. 12) is, in general, elongate-elliptical, two and one-
fourth times as long as high, well rounded anteriorly, rounded or a little
pointed posteriorly. The dorsal margin is weakly arched; the ventral
margin slightly sinuated. From above, the width is approximate to the
height, the outline of the shell is subelliptical, and the anterior part is
somewhat more pointed than the posterior. The valves are slightly beset
with hairs, each hair being set on a rather prominent papilla. Although
the shape and the actual size of the shell varies considerably, the length
to height ratio seems to remain rather constant. Sharpe (1897) gives
the size for C. simpsoni as follows: 0.73 mm. long, 0.30 mm. high, and
0.29 mm. wide. Furtos (1933) in describing C. exilis gives the length
as 0.81 mm., height as 0.38 mm., and width as 0.37 mm. The dimensions
given by Furtos are near the largest size found by the writer. Measure-
ments of several valves from Illinois specimens are as follows (mounted
in diaphane):
RIGHT LEFT
Length Height Length Height
0.78 mm. 0.36 mm. 0.80 mm. 0O.— mm.
0.72 0.33 0.74 0.34
0.73 0.33 OS 0.34
Sharpe (1897) mentions that the antennae of the female are “shorter
and thicker than usual” and this holds true in most individuals but there
OSTRACODS OF ILLINOIS—HOFF 63
is a slight tendency for the antennae to become more elongate in indi-
viduals which have nearly straight, slender furcal claws. The medial
seta of the penultimate podomere of the mandibular palp is smooth; three
setae form the group on the antepenultimate podomere of the mandibular
palp. The second thoracic leg consists of five podomeres, “terminal seg-
ment conical, approximately as long as the penultimate, which is about
as wide as long; antepenultimate segment like the penultimate,—the
three combined being but an eighth longer than the second segment.
Terminal claw as long as the last three segments” (Sharpe, 1897). In
many individuals, the three distal podomeres of the second thoracic leg
are a little longer than wide; the entire leg is more slender than shown by
Sharpe (1897:pl. 46, fig. 5).
The penultimate podomere of the third thoracic leg (fig. 13) is un-
divided. In the individuals which closely approach the original descrip-
tion of C. simpsoni, the penultimate podomere bears several minute spines
scattered over the surface. These are not always conspicuous. The ulti-
mate podomere is as wide as long. The shortest distal seta is about two
and one-half times as long as the length of the ultimate podomere.
Sharpe (1897:pl. 46, fig. 2) shows the’ shortest distal seta as being
straight; Furtos (1933) states that the seta is sharply bent near the tip
in C. exilis. Individuals which show either straight or bent setae are com-
mon; a few individuals have been observed in which the seta is recurved.
Individuals may also be found with the “reflexa” type of strongly bent
seta. In relation to the shortest distal seta, the companion seta is two to
nearly three times as long and the oppositely directed seta is about three
times as long.
The furca (figs. 14, 15, 16) is extremely variable especially in regard
to the shape of the terminal and subterminal claws. In general, the length
of the furca is between six and eight times the least width of the furcal
ramus. The dorsal seta is always long, being usually twice the least width
of the ramus, occasionally a little longer. It may be abruptly bent dorsally
near the distal end and is removed from the subterminal claw an average
of one-fourth the length of the dorsal margin of the furca. The length
of the terminal seta is usually about one-half the least width of the ramus,
but in a few individuals may be nearly as long as the least width of the
ramus. The length of the terminal claw is from one-half to two-thirds
the length of the furcal ramus. The terminal claw may vary from rather
stout to slender and is more or less curved near the tip. Both subterminal
and terminal claws are toothed, the teeth usually appearing very promi-
nent in the center of the proximal one-half of each claw. An extreme
amount of variation is shown in the subterminal claw. In the individuals
described by Sharpe (1897:pl. 46, fig. 6), the subterminal claw is de-
cidedly S-shaped (fig. 14). Furtos (1933:pl. 12, fig. 17) shows this struc-
64 ILLINOIS BIOLOGICAL MONOGRAPHS
ture in C. exilis as having at the most only a very slight tendency to be
S-shaped (fig. 15). The writer has seen both of these shapes represented
in his Illinois material with a perfect transition between the two. In
addition, the writer has observed individuals in which the subterminal claw
is very long and slender with the proximal portion straight and the distal
portion only slightly curved (fig. 16). The female genital lobe (fig. 15-G)
is poorly developed. It is represented by a small and slightly posteriorly
extended thoracic process.
Male: The male is not mentioned by Sharpe (1897, 1918). Furtos
(1933) states that the male is unknown. The present writer has seen no
mature males assignable to C. simpson. However, a few uncertain im-
mature males with entirely undeveloped copulatory organs have been
noticed in collections containing mature females of C. simpsoni. These
doubtful individuals were too incompletely developed to make certain any
identification or to merit description at this time.
Remarks: Candona simpsoni is the most variable species of ostracod
observed by the writer. It is only through a very large series of collections
that such variation can be studied. A study of single, isolated individuals
instead of a series might lead, in the instance of this species, to the de-
scription of three or possibly four species. Through observations made
upon material from sixty different localities, it has been possible to de-
termine the variation existing in this species and to demonstrate that the
series representative of the species is definitely without any sufficient
break to allow even the recognition of subspecies.
The most constant characters are size and shape of the shell. Beyond
this, most of the structures usually considered to be of specific importance
are very variable. The variability of the appendages lies chiefly in the
relative length of the entire appendage and its parts. The writer applied
statistical methods to a study of thirty individuals, representing all shapes
of the subterminal furcal claw. Measurements were made of eight differ-
ent structures of the second and third thoracic legs and the furca. From
these data, ratios were figured between the following measurements: the
length of the claw and the length of the ultimate podomere of the second
leg, the length of the short seta and the length of the ultimate podomere
of the third leg, the length of the dorsal seta and least width of the
furcal ramus, and the length of the terminal claw and least width of the
furcal ramus. In every instance except one, an unimodal curve resulted
when frequency distributions of the ratios were plotted. The one excep-
tion was the frequency curve of the ratio of the dorsal seta of the furca
and the least width of the ramus. This was a bimodal curve but there was
no correlation whatever between the two peaks of the curve and the type of
subterminal claw. From these data, the writer believes that he is justified
in stating that the unimodal nature of the curves indicate conclusively the
OSTRACODS OF ILLINOIS—HOFF 65
presence of a single species among the diversified individuals measured.
Moreover, the actual measurements of the various structures (length of
ultimate podomere and length of the claw of the second leg; length of
ultimate podomere and short seta of the third leg; and the least width,
length of the dorsal seta, and length of the terminal claw of the furca),
the distribution in Illinois, the type of habitat, and the dates upon which
the collections were made show no correlation whatever with the shape
of the subterminal claw of the furca.
Adequate transition individuals occur in which the animal displays
characters of both C. simpsoni of Sharpe and C. exilis of Furtos. In
many instances, the transition is self-sufficient to prove conclusively that
both of these species are the same. In one individual, there was found an
S-shaped subterminal claw on one side of the body and a claw of the
“exilis” form on the other side. Again, in an individual in which were
found straight furcal claws as shown in figure 16, the antennae were
stout and there were small spines on the sides of the penultimate podomere
of the third thoracic leg (fig. 13) as is characteristic of the form “simp-
soni.” This individual had the shell size and distinctly curved short
distal seta of the third leg described for the “exilis” form. Thus in some
individuals, combinations of characters may be found which definitely
unite the variable individuals into a single species. It is as easy to find
an individual with a curved short distal seta on the third thoracic leg in
the “‘simpsoni”’ form as it is in the “exilis’” form, or for that matter in
the form with straight claws; the small spines on the penultimate podo-
mere of the third leg may also be found in all three forms if sufficient
numbers of individuals are examined. There seems to be no correlation
between the curved distal seta and the small spines mentioned above, and
indeed no correlation with either of these and the type of furcal claw.
Transitions also occur between C. simpsoni and C. reflexa. In some of
the transitions, there may be found a short bent seta on the third leg as
Sharpe described for C. reflexa and a typical S-shaped subterminal claw
as found in C. simpson.
Whether or not there exists races with all of the individuals showing
one type of furcal claw is not now certain. Such a problem involving
the examination of large numbers of individuals from different localities
would merit investigation. In general, ordinary field collections as made
by the writer contain too few individuals for population analyses.
In regard to the placement of C. simpsoni in the proper group of the
genus Candona, the writer assigns this species to the group Rostrata
because there are three setae in the bundle on the antepenultimate
podomere of the mandibular palp and because the female genital lobe is
poorly developed. However, the shell length is slightly greater than twice
the height and the valves are relatively smooth, this being contrary to the
66 ILLINOIS BIOLOGICAL MONOGRAPHS
typical condition in the Rostrata group. This would tend to exclude this
species from the group. The writer holds the opinion, however, that more
consideration and weight should be given to the condition of the genital
lobes of the female than to the ratio of height to length of shell. This is
also apparently the opinion of European writers.
Ecology: Sharpe (1918) reports that C. simpsoni is a bottom form
of lakes and river shores, and also ponds, while Furtos (1933) gives the
habitat as “shallow weedy ponds and marshes.” The majority of the
writer’s seventy collections of this species were made in grass or in
masses of algae along the edge of ponds and sluggish streams. One
individual was taken from the water in a crayfish burrow. The young
of C. simpsoni may be taken from ponds before the prevernal break-up
of the surface ice. Young individuals may be taken through much of the
aestival season; the adults persist through autumn in habitats that do
not dry up during the summer. In general, the individuals of this species
are not taken in great numbers in most collections. Collections with as
many as ten individuals, however, are not rare. In only two of the
writer’s seventy collections was this species found in numbers greater
than ten. One of these collections contained twenty, the other about one
hundred individuals. This last collection was made from a temporary
pond in Woodford County, Illinois.
Distribution: Candona simpsoni appears to be the most common and
widely distributed Candoninae in Illinois. Sharpe (1897) reported it from
Havana and Urbana, Illinois. Kofoid (1908) also reported it from
Havana, Illinois. The writer has taken it in collections throughout the
state from Lake County on the north to Hardin and Johnson Counties
on the south. Furtos furnishes the only record outside of Illinois in her
reference (1933) to C. exilis in Ohio.
Group Compressa
More than three setae in the bundle on the inner margin of the ante-
penultimate podomere of the mandibular palp. Otherwise as in group
Rostrata.
Only two species assignable to the group Compressa are known from
Illinois: C. albicans Brady 1864 (C. parallela G. W. Miiller 1900) and
C. biangulata sp. nov.
KEY TO SPECIES OF THE GROUP COMPRESSA FROM ILLINOIS
a. Dorsal margin of shell straight without a sinuation between it and the anterior
shell margin (fig. 18); anterior margin of shell broadly rounded; length of
shortest distal seta of third leg is a little over twice the length of the ulti-
mate podomere (fig. 19) ; length of terminal seta of furca less than the least
width of the auitcal ramus. (fe.*20). 0.05 be hues ewes anon’ C. albicans Brady 1864
OSTRACODS OF ILLINOIS—HOFF 67
b. A sinuation between the dorsal and anterior shell margins (fig. 24) ; anterior
margin of shell narrowly rounded; length of the shortest distal seta of third
leg over three times the length of the ultimate podomere (fig. 27) ; terminal
seta of furca equal to least width of ramus (fig. 28)...... C. biangulata sp. nov.
Candona albicans Brady 1864
(Pl. II, figs. 18-23)
C. albicans Brady 1864. Brady, 1864:61, pl. 4, figs. 6-10; 1868:381-2, pl. 25, figs.
20-25 and pl. 36, fig. 12; Sars, 1928:82-83, pl. 39, fig. 1.
C. parallela G. W. Miiller 1900. G. W. Miiller, 1900:25, pl. 5, figs. 5, 6, 18, 19, 23-
25; Sharpe, 1908:401-402, pl. 51, fig. 1-5; 1918:825, figs. 1297a, b, c, d; Furtos,
1933:486-487, pl. 12, figs. 18-20; Dobbin, 1941:241, pl. 3, figs. 11-13.
Type Locality: British Isles.
Description of the Female: Candona albicans of the Compressa
group has a shell (fig. 18) sub-oval in lateral view. The dorsal margin is
nearly straight, sometimes slightly sinuated, and almost horizontal, being
nearly parallel to the ventral margin though often inclined somewhat
posteriorly. The anterior margin is broadly rounded, the posterior is
bluntly rounded. The greatest height is at the beginning of the posterior
one-fourth of the shell and is more than one-half of the length. Measure-
ments of the valves of two mature females from Illinois show a consider-
able variation in actual shell size (mounted in diaphane). These measure-
ments are as follows:
RIGHT LEFT
Length Height Length Height
0.84 mm. 0.44 mm. 0.85 mm. 0.48 mm.
0.78 0.42 0.78 0.44
In dorsal view the shell appears elongated with the greatest width in the
middle and somewhat less than the height. The posterior margin is
rounded and the anterior is somewhat pointed when viewed from above.
The valves show many hairs, especially along the anterior and posterior
margins. The shell is covered with small pits, and this areolation is
especially marked in the anterior and posterior thirds of the shell and in
young individuals.
The two longest claws of the penultimate podomere of the antenna
extend beyond the tip of the longest claw of the ultimate podomere.
The mandibular palp has a smooth medial seta on the penultimate
podomere and a bundle of four setae on the antepenultimate podomere.
The penultimate podomere of the third thoracic leg (fig. 19-P) is divided,
the shortest apical seta is slightly longer than twice the length of the
ultimate podomere in American forms and slightly less in European
specimens. The seta of the penultimate podomere is also longer than
68 ILLINOIS BIOLOGICAL MONOGRAPHS
in the European form. The furca (fig. 20) has a nearly straight posterior
margin; both claws are somewhat bent throughout their length. The
length of the ventral margin of the furcal ramus is between seven and
eight times the least width; the length of the dorsal seta is over two times
the least width of the ramus in Illinois specimens but less in the Euro-
pean. The terminal claw is less than one-half of the length of the furca
while the terminal seta has a length less than the least width of the ramus.
The genital lobe is not well developed; though inconspicuous, it has a
hemispherical shape.
Description of the Male: The single male of C. albicans collected in
Illinois has a shell (fig. 21) somewhat similar to that of the female but
larger. The right valve measures 0.94 mm. long and 0.48 mm. high; the
left valve slightly larger. The valves are not as high in relation to the
length as in the female and the dorsal margin is not so flattened or hori-
zontal. The right, but not the left, valve has a slight sinuation at the
anterior end of the dorsal margin. The antenna, mandible, and thoracic
legs are much as they are in the female. The length of the ventral
margin of the furca is ten to eleven times the least width, being much
more slender than in the female. The claws and the dorsal setae are also
proportionally larger than in the female. The prehensile palps are slightly
unequal but nearly similar. The left (fig. 22a) has a rather straight
slender distal portion while the right (fig. 22b) is more falciform and
stouter than the left. The penis (fig. 23) has less chitinized lobes than
in many Candona species. The lobes are very flap-like and flimsy in
appearance.
The occurrence of males is considered to be rare in this species.
Furtos (1933) reports the male as being unknown. Sars (1928) reports
that males are rare. He gives a description of the male whose shell
differs little in size and shape from the shell of the female. The penis
and prehensile palps of the male are said by Sars (1928) to be similar
to those of C. stagnalis G. O. Sars 1891 in which the penis has “three
well defined terminal lappets of nearly equal size, though somewhat
differing in shape” (Sars, 1928) and the prehensile palps are unequal
and dissimilar, the left being fairly straight and the right subfalcate
(Sars, 19287pl. S& fie. 2).
Remarks: The C. albicans found by the writer agrees in most details
with the European descriptions and is identical with the Ohio specimens
described by Furtos (1933). The short apical seta of the third thoracic
leg and the dorsal seta of the furca as well as the seta of the penultimate
podomere of the third leg are longer than shown in the descriptions by
European writers. The figures given by Sharpe (1908:pl. 51, figs. 3 and 5)
for C. parallela are very close to the specimens found by Furtos in Ohio
and those collected by the present writer. Apparently there is a slight
OSTRACODS OF ILLINOIS—HOFF 69
consistent difference between the European and the American forms.
Until larger numbers of individuals are examined from many different
localities, it is thought unwise to assign any new specific or even varietal
designation to the American form.
For forty years the species under discussion has been known almost
universally as C. parallela G. W. Miller 1900. After a thorough examina-
tion of the description of Candona albicans Brady 1864 (Brady, 1868),
there is little doubt in the writer’s mind that the species described by
Brady in 1864 is the same as the one described by G. W. Muller in 1900.
The chief apparent difficulty in establishing synonymy between C. albicans
and C. parallela seems to be the smaller size of the former. In spite of this
difference, a result of Brady possibly basing his description on immature
individuals, Sars (1928) proves almost conclusively that C. albicans is the
valid name. His arguments are founded on structural resemblances as well
as surface sculpturing. Disregarding Sars’s demonstration of the validity
of C. albicans, Klie (1938a) tenaciously holds to the name C. parallela;
he gives, however, C. albicans as a synonym of C. parallela. To retain
C. parallela as the valid name under these circumstances is contrary to
law of priority in the rules of nomenclature. Beyond all doubt, C. albicans
is the valid name and must be retained for this species.
Ecology: The habitat of this species in North America seems to be
identical with the habitat as recorded for Europe. Sars (1928) reports
it as being common in small ditches and pools with muddy bottom. Klie
(1938a) gives the habitat as temporary pools with muddy bottom and
rich plant growths. Sharpe (1918) reports the habitat as “swampy
ponds”; Furtos (1933) found the species in temporary and permanent
pools and swamps in Ohio. The present writer secured some of his speci-
mens from a small pool four feet in diameter and not over ten inches
deep located just a few feet from the edge of Lake Vermilion at Danville,
Illinois, on April 28, 1940. The bottom of the pool was of mud and
grass was growing around the edge. Other collections of this species were
made in July from temporary streams. C. albicans seems to be distinctly
a vernal and early aestival form. The males are herein for the first time
reported from North America. From the sparsity of the males, it is
probable that reproduction in this species is almost entirely partheno-
genetic.
Distribution: C. albicans has been reported from continental Europe
and from the British Isles by numerous writers. That it is probably dis-
tributed widely in the United States is shown by the report from Colorado
by Sharpe (1908), from Ohio by Furtos (1933), and from California by
Dobbin (1941). It was obtained by the writer in four collections from
Illinois: one from Vermilion County on April 28, 1940, and three from
Carroll County on July 5, 1940.
70 ILLINOIS BIOLOGICAL MONOGRAPHS
Candona biangulata sp. nov.
(Pl. II, figs. 24, 25; pl. III, figs. 26-28)
Candona acuminata Sharpe 1897 (non Fischer 1851). Sharpe, 1897:449-451, pl. 44,
figs. 5-7.
Type Locality: MUlinois.
Description of the Female: A Candona of the Compressa group.
From the side, the shell (fig. 24) is elongated; height slightly greater
than one-half of the length. The greatest height of the shell is at the
posterior end of the flattened dorsal margin. The right valve shows a
ventral margin with a slight, even sinuation most marked near the center
of the margin. The dorsal margin is very slightly concave, very slightly
convex, or in most shells straight. Between the dorsal margin and the
anterior margin is a pronounced sinuation. The anterior margin is nar-
rowly rounded. A shallow sinuation lies between the dorsal margin
and the posterior margin and in some individuals may be more or
less obliterated. The posterior margin is rather broadly curved with a
tendency for the arc to become slightly straightened on approaching the
ventral margin. The left valve differs in shape distinctly from the right
valve although the ventral margin is somewhat similar. The dorsal margin
is convex and the sinuations between the dorsal margin and the anterior
and posterior margins are not noticeable but may be expressed by a
slightly flattened area near both ends of the dorsal margin. The left valve
is slightly larger than the right, the height especially being greater. The
subcentrally located muscle scars are six in number and display a
definite arrangement in all the individuals examined. A single, oval to
elongate isolated scar is dorsal to a group of five circular to oval scars
arranged in an imperfect rosette. The ovary appears as an elongated,
narrow band and reaches the level of the muscle scars. The pore-canals
are very short and inconspicuous because the submarginal line is removed
but a short distance from the shell margin. The valves are nearly devoid
of hairs, though a few bristle-bearing puncta are scattered over the
surface. The hairs of the anterior and posterior margins are short and
weak. Measurements of the valves of three mature females from Illinois
are as follows (mounted in diaphane):
RIGHT LEFT
Length Height Length Height
0.71mm. 0.36 mm. 0.73 mm. 0.— mm. (holotype)
0.70 0.35 0.72 0.38
0.70 0.36 Oss 0.38
A dorsal view of the shell was not obtained but observations of mounted
valves indicate that the width of the shell is probably one-fourth to one-
fifth less than the height.
The antennules are composed of eight podomeres. The third and
OSTRACODS OF ILLINOIS—HOFF 71
fourth podomeres have a length approximate to the width. The distal
four podomeres are much longer than wide, especially the ultimate
podomere which is in the form of an elongated cylinder. The third
podomere has a short seta equal to the width of the podomere; the fourth
has no seta; the fifth has two long swimming setae; and the sixth has,
in addition to two long swimming setae, a short seta equal to the width
of the podomere. The seventh podomere has two long swimming setae
and two short ones slightly less in length than the length of the
podomere. The apical setae consist of a short, heavy seta equal in length
approximately to the length of the ultimate podomere and two long
swimming setae. The antennae consist of five podomeres. The medial
side of the third (antepenultimate) podomere bears in addition to the
regularly occurring sensory bristle a pair of setae, each slightly longer
than the sensory bristle and separated from the distal margin of the
podomere by a distance equal to one-half of the width of the podomere
taken at the base of the setae. The penultimate podomere is shorter than
the antepenultimate and bears two medial setae, one close to the distal
margin and the other located proximally a distance equal to the width of
the podomere. The penultimate podomere also has a short lateral seta
close to the beginning of the distal one-third of the podomere. The ulti-
mate podomere has a width slightly greater than one-half the distal width
of the penultimate podomere. The longest claws of the penultimate podo-
mere are equal to or extend slightly beyond the longest claw of the
ultimate podomere. The teeth of the mandible are long and pointed; the
mandibular palp (fig. 25) is characteristic of the Compressa group as the
median seta on the penultimate podomere is unfeathered and there are
four setae in the group (fig. 25-B) on the antepenultimate podomere.
Eighteen rays are present on the branchial plate of each maxilla. The
penultimate podomere of the palp of the maxilla is twice as long as the
width measured in the distal one-third where the podomere is considerably
widened.
The second thoracic leg (fig. 26) has a very large, heavy second
podomere (fig. 26-A) whose length is equal at least to the combined
lengths of the three more distal podomeres. The antepenultimate podo-
mere and the penultimate podomere are subequal in length; the ultimate
podomere (fig. 26-U) is conical with the length slightly greater than the
width of the base. The second podomere has a short subterminal seta
equal to the distally placed seta of the third or antepenultimate podomere.
The seta of the penultimate podomere is approximately as long as, or
longer than, the length of the last podomere. The claw (fig. 26-C) of the
ultimate podomere is one and one-fourth to one and one-half times the
combined length of the last three podomeres. The ultimate podomere
also has two short setae, one of which is shorter than the length of the
72 ILLINOIS BIOLOGICAL MONOGRAPHS
distal podomere, the other somewhat longer. The third thoracic leg (fig.
27) has five apparent podomeres as the penultimate podomere is clearly
divided. The apparent penultimate podomere bears a seta consider-
ably greater in length than the length of the podomere. The ultimate
podomere is nearly square in lateral view; the shortest distal seta is
longer than the seta of the penultimate podomere and is over three times
the length of the ultimate podomere. The longer distal seta of the pair
is over one and one-half as long as its shorter companion and is about
equal in length to the combined lengths of the three apparent distal
podomeres of the third leg. The third distal seta is about one and one-
fourth the length of the longer seta of the pair, although considerable
variation is shown in the length.
The furca (fig. 28) has a relatively straight dorsal margin; the dorsal
seta stands at the apex of a slight convexity; a small indentation in the
dorsal margin between the proximal one-half and one-third of the
dorsal margin indicates the deepest point in a slight concavity. The
ventral margin of the furca is slightly but evenly curved. The least width
of the ramus is equal to about one-seventh of the ventral margin. The
dorsal seta has a length about two and one-half to three times the least
width of the ramus and is located from the base of the subterminal claw
a distance of at least twice the least width of the ramus. Both the sub-
terminal and the terminal claws are similar. in appearance, being gently
curved, long, and slender. The subterminal claw is about six-sevenths as
long as the terminal, while the terminal claw is more than one-half and
less than two-thirds as long as the dorsal margin of the ramus. No
indication of teeth or hairs could be found on the claws although observa-
tions were made under high magnification on both diaphane and glycerine
mounted materials. The terminal seta is equal to the least width of the
ramus. The female genital lobe (fig. 28-G) is small and cone-shaped;
often it is distally drawn out papilla-like. The lobe does not extend
posteriorly beyond the margin of the furcal rami.
Male: The male is unknown.
Remarks: It is rather difficult to compare C. biangulata sp. nov. with
other forms of the group Compressa because of the imperfect nature of
the literature concerning the external morphology of many forms. In only
three previously reported species belonging to the Compressa group, as far
as the writer has been able to determine, have four setae been definitely
reported in the mandibular bundle. These species are: C. albicans Brady
1864, C. hertzogi Klie 1938 (Klie, 1938d), and C. bilobata Klie 1938
(Klie, 1938c). Of these three, C. albicans alone has a divided penulti-
mate podomere in the third thoracic leg and, as a result, it is apparently
related to C. biangulata. One of the species which has a questionable
OSTRACODS OF ILLINOIS—HOFF 73
number of setae in the mandibular bundle and which may be related to
C. biangulata is C. aemonae Klie 1935 (Klie, 1935). Klie does not know
for certain whether the bundle of setae on the antepenultimate podomere
of the mandibular palp in C. aemonae has four or five setae. The third
thoracic leg, the furca, and in part the genital lobe are similar to C. bi-
angulata. Both C. biangulata and C. aemonae have two setae on the
basal podomere of the third leg. On the other hand, the shape of the
shell differs greatly in the two species. Whether or not the two species are
closely related must await the determination of the number of setae in
the bundle on the mandibular palp in C. aemonae.
The writer believes that the ostracod described by Sharpe (1897)
under the designation of C. acuminata was not the C. acuminata of
Fischer. That Sharpe himself realized his error is evident from the fact
that he later (1918) does not give Illinois as a locality for C. acuminata
Fischer. Although the shell described by Sharpe is slightly larger than
that of C. biangulata, there is so much similarity between the description
given for C. acuminata by Sharpe and the individuals of the present new
species, that there can be little question but that they are the same. The
present writer gives an entirely new description without reference to
Sharpe’s description because it is possible that Sharpe’s description may
be contaminated from European descriptions of C. acuminata Fischer.
Ecology: This species has been taken by the writer in five collections,
each containing only one or two individuals. Two collections were from
temporary streams, two from vernal ponds. The fifth collection was
secured from water in a crayfish burrow. Sharpe (1897) collected his
material from a pond. Obviously, this species lives in temporary waters
where there is little or no current. It is usually found over a mud
bottom.
Distribution: C. biangulata sp. nov. was secured by the writer from
Champaign, McLean, Will, and Henry Counties, Illinois. Sharpe (1897)
reported this species as C. acuminata from Clifton, Iroquois County, Illi-
nois on May 12, 1882.
The holotype (female) of this species is deposited in the U. S. National
Museum (Cat. No. 81067). One paratype (female) is in the collection
of Dr. H. J. Van Cleave and others (female) are retained in the writer’s
collection.
Group Acuminata
Shell compressed, width usually about one-third of the length; height
often but not always less than one-half the length; posterior end of shell
broadly rounded (fig. 49) or obliquely subtruncate to truncate (fig. 40).
Shell with few hairs. The medial seta of the penultimate podomere of
the mandibular palp smooth; the bundle on the antepenultimate podomere
74 ILLINOIS BIOLOGICAL MONOGRAPHS
consists of four setae (fig. 43-S). The female genital lobe is well
developed, pointed, and extends posteriorly between the furcal rami
(figs. 32-G, 37-G). Outer lobe of the penis usually well developed and
conspicuous (figs. 48-O, 57-O).
The group Acuminata appears to have reached a high degree of
development in North America where there are many more species than in
Europe. The exact number of North American species assignable to this
group is unknown because the knowledge regarding the minute structure
of many species is incomplete. The deficiency of information is especially
acute in regard to the number of setae in the bundle on the mandibular
palp. It is probable that many of the new species described by Furtos in
1933 belong to this group.
The present writer has definitely assigned eight species from Illinois
to this group and two more are assigned tentatively until more details
of the structure can be secured. The tentative assignment of these two
species, C. recticauda Sharpe 1897 and C. sharpei sp. nov., is based upon
inadequate descriptions.
KEY TO SPECIES OF THE GROUP ACUMINATA IN ILLINOIS
la. The antepenultimate podomere of the second thoracic leg is two-thirds as
long as the penultimate podomere; the length of the longer companion
distal seta of the third thoracic leg is more than three times the length of
tHE SHOLtE RLOME sera cees csere reer Reererac uote se oka teeta areata Poets C. recticauda Sharpe 1897
b. The antepenultimate podomere of the second thoracic leg as long or longer
than the penultimate podomere; the length of the longer companion seta of
the third leg is less than three times the length of the shorter of the pair
Cig BBS) oe sale asso Be Sb we ial iGa te tnkoee iscene pfenaithe, ciate oi eile a) ctaatele ts eae 2
2a. Ventral margin of furca not over eight times the least width of the furcal
ioe STE Ch en ee oy AR ee aE OM Are tecture MrT) MG Ait aeyn B1G.c C. sharpet sp. nov.
b. Ventral margin of furca over eight times the least width of the furcal
TALLYAUUS Stele raccecs, clea ic ats te erlotcso eierses so euro wits ast auc vnevet cote ov ees Acielfe ett ately ae oe a ana 3
3a. Female genital lobe bifurcated, ventral part not as well developed as the
dorsal branchia(hip? 30-G) a. fe yacateasnae oO Soler le etan alee C. distincta Furtos 1933
b. Female genital lobe not bifurcated but drawn out to a single point (fig.
CY EC) ee are IPSEC GAGE coo 7 4
da. Dorsal margin of shell forms a low arch without conspicuous sinuation
or angulation’ (figs. 33, 36) i. ssccite tse acca ce wee ee bic cs cu Set 5
b. Dorsal margin of shell forms a high peak usually with, occasionally with-
out, angulations, sinuations, or both (figs. 40, 49) .......... 000. cee weenie 6
Sa. Shell longer than 1.10 mm.; ventral margin of furcal ramus eleven times
and the dorsal seta two times the least width of the ramus (fig. 35)......
See Rat EG Cacho ceo OO OE Hod Oe C. caudata Kaufmann 1900
b. Female shell less than 1.10 mm. in length; ventral margin of furcal ramus
less than ten times and dorsal seta over three times the least width of the
PELTALLS (L1G BI) tasters lone et are stot Sera RevetiaR a aylianeaxc nee, Sta, C. sigmoides Sharpe 1897
6a. Length of the female shell over 1.25 mm.......... C. crogmaniana Turner 1894
b. Length of female shell) less than 1-25 mm.:....... 60. 000enc os, ou)s ott 7.
OSTRACODS OF ILLINOIS—HOFF 75
7a. The dorsal margin of the shell high and rounded (fig. 40); outer lobe of
penis distally divided (fig. 48-O) ; longer companion seta of third leg more
than twice the length of the shorter of the pair (fig. 45)...C. indigena sp. nov.
b. The dorsal margin of the shell usually not high and well rounded; outer
lobe of penis not distally divided; third thoracic leg with length of the
longer companion distal seta equal to or less than twice the shorter of the
EM SS yas Sc 2 Scare as afro: Gaara nce: & betes acces & w CERIe epeedael lah ec alaisenes be aone's! = 8
8a. Posterior slope of shell of female sculptured (figs. 58, 59); female genital
foberione; and finger-like (fig: 62)... 0s. 00sec. 0 sca eees se C. fossulensis sp. nov.
b. Posterior slope of shell not sculptured; female genital lobe not finger-form...9
9a, Shell without posterior-ventral angulation (fig. 49); posterior end of shell
rounded; female genital lobe not especially narrowed at junction with the
grespane: (Gere EX CS ck eee RCE ICL HOM CRORE Me TER OTe Sa Car C. suburbana sp. nov.
b. Shell with posterior-ventral angulation (fig. 65); posterior end of shell
subtruncate; female genital lobe narrowed at junction with the thorax
Uiys,, (0:(G)) Se atos COe SAIS teat ete rearhanr orate rine nGr ren Orcrier C. acuta sp. nov.
Candona recticauda Sharpe 1897
Candona recticauda Sharpe 1897. Sharpe, 1897:451-452, pl. 46, figs. 7-11; 1918:826,
figs. 1299a, b, c, d, e.
Type Locality: Clifton, Iroquois County, Illinois.
Description (after Sharpe, 1897): A Candona species tentatively
assignable to the Acuminata group. “Shell of male 1.18 mm. long and
.70 mm, high, stout.” Both prehensile palps gently bent, the right much
heavier than the left and ending in a hyaline point. Terminal claw of
the second leg is one and one-half times as long as the sum of the
lengths of the distal three podomeres; the antepenultimate podomere is
two-thirds as long as the penultimate. The third thoracic leg has the
penultimate podomere divided; the ultimate podomere is as long as wide,
with the length of the shortest distal seta two and one-half times the
length of the ultimate podomere. In Sharpe’s figure 7, plate 46, however,
the length of this seta appears about one and one-half times the length of
the ultimate podomere. The companion seta is about three and one-half
times the length of the shorter of the pair. “Caudal rami well developed,
long, straight. Terminal claw half as long as the ramus, evenly and gently
curved .... Dorsal seta three fifths the length of the subterminal claw
and at two thirds its length from the claw; terminal seta a third the
length of the dorsal one.”
Remarks: This description by Sharpe appears to be based entirely on
males. The present writer has found no specimens which could be iden-
tified as C. recticauda Sharpe. This species seems related to C. indigena
sp. nov. from which it differs in the shape of the prehensible claws, the
relative lengths of the antepenultimate and penultimate podomeres of the
second thoracic leg, and the length of the short seta of the ultimate podo-
76 ILLINOIS BIOLOGICAL MONOGRAPHS
mere of the third thoracic leg. Since Sharpe gives neither a description
nor a figure of the shell, accurate identification of specimens belonging
to C. recticauda may be difficult. For the present, C. recticauda should be
considered a valid species.
Ecology: Sharpe (1897) secured his type specimens from a pond.
Distribution: The only available record for C. recticauda is that of
the type specimens from Clifton, Iroquois County, Illinois (Sharpe,
1897).
Candona shar pei sp. nov.
Candona fabaeformis Sharpe 1897 (non Fischer 1851). Sharpe, 1897:454-455, pl.
45, figs. 1-3.
Candona fabaeformis (part?) Sharpe 1897 (non Fischer 1851). Sharpe, 1918:826,
figs. 1300a, b, c, d.
Type Locality: (C. fabaeformis Sharpe 1897) Normal, McLean
County, Illinois.
Description (after Sharpe, 1897): A Candona species possibly be-
longing to the group Acuminata. “Length 1.00 mm., height .47 mm.,
width; A9 mim. <2 2: Seen from the side, it is slightly widest back of the
middle, the upper and lower edges nearly parallel, both ends fully rounded,
the ventral edge quite deeply sinuate near the middle.” Terminal claws of
the female antenna scarcely longer than last two podomeres. The penulti-
mate podomere of the third leg divided. “Terminal segment as long as
broad, one half as long as the penultimate segment, which is twice as
long as broad. Shorter terminal seta twice as long as the terminal segment
and a third as long as the longer similarly directed seta; reflexed seta but
slightly longer than the longer terminal one.” The furca is seven times
as long as wide; terminal claw one-third as long as the ramus. The
terminal seta is as long as the ramus is wide; “dorsal seta four-fifths
as long as the subterminal claw, and distant twice the width of the ramus
from it.”
Remarks: This species, which has been renamed C. sharpei sp. nov.,
cannot possibly be the C. fabaeformis of Fischer. G. W. Miller (1912)
doubted Sharpe’s designation of this form. By the shell width alone, it
is possible to see that Sharpe’s species is not C. fabaeformis Fischer. The
species described by Sharpe under C. fabaeformis had a shell width of
one-half the length while the C. fabaeformis of Fischer has a shell width
of not over one-third of the length (G. W. Miiller, 1900; Klie, 1938a;
et alli). Also the furca in Sharpe’s species is much stouter, having a
length of less than seven times the width, while in Fischer’s C. fabae-
formis the furca is elongated and has a length of at least eleven times the
least width.
OSTRACODS OF ILLINOIS—HOFF 77
Sharpe apparently studied only female shells as he does not mention
the male, and in particular the prehensile claws. However, he pictures the
right prehensile claw (1918:fig. 1330d) at a later time. It is entirely
possible that this illustration was borrowed from European descriptions of
the true C. fabaeformis. In regard to Turner’s report (1895) of C. fabae-
formis in Georgia, it is apparent (Cf. G. W. Miller, 1912) from a study
of the shell characters that it is also not assignable to C.. fabaeformis of
Fischer. At the same time, it is doubtful if the specimens described by
Turner (1895) and Sharpe (1897) belong to the same species as they
appear to differ in many respects.
A definite assignment of C. sharpei sp. nov. to any certain group of
the genus Candona is of course impossible. If one knew for certain that
Sharpe (1918:fig. 1300d) pictured the right prehensile palp from an
Illinois individual, there would be little hesitancy in referring this species
to the group Fabaeformis. Moreover, assignment to any group is diff-
cult because the condition of the female genital lobe is unknown. In
general appearance, the writer suspects that the species probably belongs
to the Acuminata group and is related to such forms as C. acuta and
C. sigmoides. It is entirely possible that Sharpe based his species diag-
nosis on immature individuals. At any rate, the writer is of the opinion
that C. sharpei sp. nov. should be carried in the literature until the Can-
doninae of the state are better known and the variation occurring within
species is understood. It may then be possible to place this species.
Ecology: Sharpe (1897) reports this species from a pool.
Distribution: The only certain reference to C. sharpei sp. nov. is that
of Sharpe (1897) who reported it under the name C. fabaeformis from
Normal, Illinois on March 27, 1881.
Candona distincta Furtos 1933
(Pl. III, figs. 29-30)
Candona distincta Furtos 1933. Furtos, 1933:478-479, pl. 8, fig. 15; pl. 9, figs. 13-16;
pl. 12, figs. 21-22.
Type Locality: Ohio.
Description of the Female: A Candona of the Acuminata group (fig.
29). “From the side: elongated, height about one-half the length;
extremities rounded, the posterior narrower; ascending slope of the
dorsal margin moderately arched, with a distinct sinuation in the middle
giving the appearance of two dorsal humps, the posterior of which is
the higher; descending slope of dorsal margin almost straight; ventral
margin sinuated; submarginal line removed from the mid-central and
78 ILLINOIS BIOLOGICAL MONOGRAPHS
posterior margins” (Furtos, 1933). The measurements of valves of two
females from Illinois mounted in diaphane are:
RIGHT LEFT
Length Height Length Height
0.92 mm. 0.47 mm. 0.93 mm. 0.49 mm.
0.97 0.50 0.98 0.52
The penultimate podomere of the third leg is divided. In the material
from Illinois, the shortest distal seta of the third thoracic leg is nearly
four times the length of the ultimate podomere while the companion seta
is slightly under two and the oppositely directed seta slightly over two
times the length of the shortest seta. The ventral margin of the furca
(fig. 30) is eight or nine times the least width of the furcal ramus; the
length of the dorsal seta is about three times and the length of the
terminal seta about one and one-fourth times the least width of the ramus.
The dorsal seta is removed from the subterminal claw by a distance equal
to three times the least width of the ramus. “Genital lobes moderately
developed, proximal portion rectangular, slightly longer than broad,
distal process somewhat forked, the ventral branch barely developed”
(Furtos, 1933).
Description of the Male: ‘Male larger than the female, left valve
larger than the right, projecting beyond it at each extremity, sinuation of
dorsal margin less pronounced, ventral margin with a small anterior
hump, behind which the sinuation is deeper than in the female” (Furtos,
1933). The sizes of valves of three males from Illinois (mounted in
diaphane) are as follows:
RIGHT LEFT
Length Height Length Height
1.00 mm. 0.53 mm. 1.01 mm. 0.54 mm.
1.02 0.56 1.04 O77
1.05 0.55 OG 0.56
Remarks: The Illinois material agrees precisely with the original
description of Furtos (1933).
Ecology: Furtos (1933) reported this species as common in marshes,
canal basins, and small lakes. The present writer collected his specimens
from a small temporary prairie pond and a grassy roadside ditch. Like
many other Candona species, this form is apparently vernal in seasonal
distribution.
Distribution: Furtos (1933) reported C. distincta from several locali-
ties in Ohio. The present writer’s collections were secured from Seymour
Prairie, Champaign County, on April 1, 1940, and from the same vicinity
but in Piatt County, Illinois, on May 4, 1940.
OSTRACODS OF ILLINOIS—HOFF 79
Candona crogmaniana Turner 1894
(Pl. III, figs. 31-32)
Candona crogmaniana Turner 1894. Turner, 1894:20-21, pl. 8, figs. 24-33; Furtos,
1933:476, pl. 8, figs. 1-3; pl. 9, figs. 17-18; pl. 11, figs. 9-10.
Candona crogmani Turner 1895. Turner, 1895:300-301, pl. 71, figs. 24-33; pl. 81,
figs. 4-5; Sharpe, 1918:824, figs. 1295a, b, c.
Type Locality: Atlanta, Georgia.
Description of the Female: A Candona of the Acuminata group.
“From the side: elongated, subtriangular, height less than one-half the
length, highest in the posterior third; anterior extremity broadly rounded,
the posterior narrow; ascending slope of dorsal margin gently arched,
with an anterior sinuation, descending slope steep; ventral margin
sinuated” (Furtos, 1933). The shell (fig. 31) is large; valves of three
mature females from Illinois (mounted in diaphane) measure as follows:
RIGHT LEFT
Length Height Length Height
1.32 mm. 0.65 mm. 1.3/7 mm. 9) 0/68 min,
1.41 0.68 1:45 0.70
1.28 0.63 1.33 0.65
The mandibular palp has the medial-distal seta of the penultimate
podomere smooth and has four setae in the bundle on the antepenulti-
mate podomere. The penultimate podomere of the third thoracic leg is
divided; the distal podomere is nearly as wide as long; and the shortest
distal seta is four times the length of the distal podomere. The companion
seta is two and one-half times as long as its shorter mate, and the op-
positely directed seta is three times as long as the shortest distal seta.
The furca is gently curved; the ventral margin is twelve to thirteen
times the least width. The dorsal seta has a length of over four times
the least width of the ramus and is removed from the subterminal claw
by a distance equal to almost four times the least width of the ramus.
The terminal claw has a length approximate to one-half of the length of
the ventral margin of the ramus while the terminal seta has a length
approximate to twice the least width of the ramus. The genital lobe (fig.
32-G) consists of a long finger-like projection extending posteriorly and
dorsally from a bulbose base.
Description of the Male: With the exception that the shell size is
slightly larger in the male than in the female and that the shape is some-
what different, the anatomical details of the male and the female are the
same. No males were observed by the writer in his material collected
in Illinois. The reader is referred to Furtos’s description of the male
(Furtos, 1933).
Remarks: Furtos is correct in assigning to this species the older name
80 ILLINOIS BIOLOGICAL MONOGRAPHS
given by Turner instead of the later name, Candona crogmani, which
Turner tried to introduce in 1895. He probably thought that crogmani
was a much simpler name and orthographically more correct than crog-
maniana. The original name must stand, however, as the valid designation
for this species.
Ecology: Turner (1894) collected the original lot of specimens from
shallow ponds near South River, Atlanta, Georgia. Turner (1895) de-
scribes these ponds as “drying up in warm weather.” Furtos (1933)
collected C. crogmaniana from both permanent and temporary ponds.
The present writer has taken this species along the edge of a permanent
pond (ox-bow) both from masses of floating algae and from dead leaves
and grass on the bottom.
Distribution: Candona crogmaniana was collected by Turner (1894)
from near Atlanta, Georgia; by Furtos (1933) from several places in
Ohio; and by the present writer from near Muncie, Vermilion County,
Illinois. The writer’s two collections came from Muncie pond on April
28, 1940.
Candona caudata Kaufmann 1900
(BEIM figs. 33-35),
Candona caudata Kaufmann 1900. Kaufmann 1900a:365-368, pl. 24, figs. 16-20; pl.
26, figs. 17-23; Sars, 1928:76-77, pl. 35; Klie, 1938a:68, figs. 223-225.
Candona elongata G. W. Miller 1912 (non Herrick 1879). G. W. Muller, 1912:140.
Type Locality: Switzerland, Europe.
Description of the Female: “Shell rather elongate, seen laterally,
narrow reniform in shape, with the greatest height not nearly attaining
half the length, dorsal margin gently arched, without forming any dis-
tinct angular bend either in front or behind, posterior obliquely produced
and exerted to a rather prominent peculiarly deflexed corner more fully
developed on the left valve, this corner being however quite obsolete in
immature specimens ;—seen dorsally, narrow elliptical in outline, with
the greatest width only slightly exceeding one-third of the length, both
extremities obtusely pointed” (Sars, 1928) (fig. 33). Measurements of
mature females (valves mounted in diaphane) from Illinois are as
follows: :
RIGHT LEFT
Length Height Length Height
1.26 mm 0.60 mm. 1.31 mm 0.63 mm
1.30 0.60 1.34 0.62
1:26 0.60 1.30 0.61
1110 0.50 1 hs 0.51
The valves are sparsely haired and are marked by minute elevated areas
separated by fine grooves. The pore-canals are rather conspicuous.
OSTRACODS OF ILLINOIS—HOFF 81
That this species belongs to the Acuminata group is evidenced by the
fact that the medial-distal seta of the penultimate podomere of the man-
dibular palp is smooth and there are four setae in the group on the
antepenultimate podomere of the same palp. The antennules and the
antennae are stouter and heavier than in many of the Candona; the
distal claws of the antennae are spine-like and the setae of the antennules
are short. The respiratory plate of the maxilla has twenty-two rays or
setae, four of which are directed orally. The second thoracic leg has
clusters of small hairs and isolated spines along the sides of the second,
third, and fourth podomeres. The third thoracic leg (fig. 34) has the
penultimate podomere divided; the seta of the penultimate podomere is
shorter than the shortest distal seta of the appendage. The ultimate
podomere is nearly square; the shortest seta is about four times the length
of the ultimate podomere. The longer seta of the similarly directed pair
is one and one-half times as long as its shorter companion while the
oppositely directed seta is nearly twice as long as the shortest distal seta.
The length of the ventral margin of the furca (fig. 35) eleven times
the least width; the length of the dorsal seta twice the least width; and
the terminal seta about the same length as the ramus is wide. The terminal
claw has a length about equal to one-half of the length of the furca and
the dorsal seta is separated from the subterminal claw by a distance
approximate to one-third of the length of the ventral margin of the
ramus. A short but conspicuous seta is located on the body dorsal to the
furca. The genital lobes form a prominent conical lappet.
Male: The male is unknown both in Europe and in the material col-
lected by the present writer (Cf. Sars, 1928; Klie, 1938a).
Remarks: There can be little question but that this is the Candona
caudata described by Kaufmann. There seem, however, to be a few minor
differences between the American specimens and the description given by
Kaufmann. The shell of the American form is often slightly higher in
proportion to the length. All of the setae of the third thoracic leg appear
to be longer in relation to the length of the podomeres in American than
in European forms but the ratios between the various setae lengths are
about the same. One of the most conspicuous differences between the
specimens from Illinois and the original specimens described by Kauf-
mann (1900a) is in the dorsal seta of the furca. In the type material,
Kaufmann describes the dorsal seta as being feathered. The American
specimens have a smooth and perhaps a little longer dorsal seta than that
described from European material. That the smooth condition is common
in Europe, where it is considered of insufficient importance to separate
species, is evidenced by both Alm (1916) and Sars (1928) who figure a
smooth dorsal seta. As the differences between the American and
82 ILLINOIS BIOLOGICAL MONOGRAPHS
European individuals are so slight and within the acknowledged range of
individual variability, the writer does not hesitate to place the Illinois
specimens in the species C. caudata Kaufmann.
A comparison of C. caudata with several closely related species is
given in the “remarks” under C. acuta sp. nov., described herein.
Ecology: European writers (Kaufmann, 1900a; Sars, 1928; et allz)
report C. caudata chiefly from canals and lakes. Of the four collections
of this species made by the writer, two came from silt bottomed drainage
ditches with grass, weeds, and algae along the edge; the third from a
permanent pond (ox-bow) ; and the fourth was taken from the stomach
of a fish, Catostomus commersonu, taken from the stripland ponds near
Oakwood, Illinois.
Distribution: Candona caudata Kaufmann 1900 is one of the com-
mon species of Europe and is well distributed over central and northern
Europe as well as the British Isles. The present report is the first from
North America. The writer’s collections of this species were all from
Vermilion County, Illinois.
Candona sigmoides Sharpe 1897
(Pl. III, figs. 36-38)
Candona sigmoides Sharpe 1897. Sharpe, 1897:455-456, pl. 45, figs. 4-11; Kofoid,
1908:258; Sharpe, 1918:825, figs. 1298a, b, c, d.
Type Locality: Mason County, Illinois.
Description of the Female: A Candona of the Acuminata group in
which the shell height is nearly equal to one-half of the length. The
valves of the shell differ somewhat in lateral view. The left valve (fig.
36) is the larger both in length and height; the greatest height is in the
posterior one-third of the valve. The dorsal margin of the left valve is
fairly evenly arched passing into the anterior and posterior margins with-
out pronounced sinuation or angulation. The angulation formed by the
posterior and ventral margins is distinct and projects somewhat into a
weak point, just anterior of which is a slight sinuation of the ventral
margin. The anterior end is somewhat narrowly rounded. There is a
sinuation in the center of the ventral margin with a convexity located
about one-half the distance from the ventral sinuation to the posterior-
ventral point. The right valve is somewhat different in shape. There
is a well marked sinuation between the dorsal margin and the anterior
margin; there is a slight angulation at the juncture of the dorsal and
posterior margins and the posterior-ventral point is not as well developed.
There is also less of a convexity in the ventral margin between the ventral
sinuation and the posterior-ventral point which is very weakly pro-
nounced in the right shell half.
OSTRACODS OF ILLINOIS—HOFF 83
Measurements of the valves of three mature females from Illinois
are as follows (mounted in diaphane) :
RIGHT LEFT
Length Height Length Height
OZmm. 0.52 mm. 1.06mm. 0.56 mm,
1.05 0.52 1.07 0.54
1.02 0.52 1.06 0.54
The shell surface is smooth with a few scattered hairs. These are best
developed around the posterior-ventral point and along the anterior
margin. The submarginal line is close to the margin so that the pore-
canals are very short. There is a group of five muscle scars arranged in
a rosette with a single scar just anterior to the group. There are also two
pairs of scars: a pair of very small scars located some distance anterior-
dorsal from the group, and another pair, each of which is well separated
and large, located a little distance anterior and ventral of the group. A
view of the shell from above was not obtained.
The antennules are stout with many of the podomeres appearing
square in side view; the setae of the antennules are much shorter and
heavier than in most Candoninae. The antennae are short and stout. The
outer margin of the penultimate podomere of the antenna bears a seta
almost in the center of the margin; the antepenultimate podomere bears
a pair of medial-distal setae which extend past the base of the distal
claws. The mandibular palp has the medial seta on the penultimate podo-
mere smooth and the bundle on the antepenultimate podomere consists of
four setae.
In the second thoracic leg, the distal claw is equal to the sum of the
lengths of the last three podomeres. The ultimate podomere is more
nearly cylindrical than conical and is over one-half as long as the penulti-
mate podomere. The third thoracic leg has the penultimate podomere
divided; the ultimate podomere is square and its shortest distal seta
has a length nearly four times the length of the podomere. The seta of
the penultimate podomere is as long as the sum of the lengths of the
apparent penultimate and antepenultimate podomeres ‘and about one-
fourth again as long as the shortest distal seta. The distal seta, com-
panion to the shortest one, is about two and one-fourth times as long as
the short seta and the oppositely directed one is about the same length as
the longer of the pair. The basal podomere of the third thoracic leg has
two setae. The furcal rami (fig. 37) are considerably curved; the ventral
margin of each measures nine or nine and one-half times the least width.
The dorsal seta has a length of three and one-fourth times the least width
of the ramus and is located from the subterminal claw a distance equal to
three times the least width. The terminal seta (fig. 37-S) has a length
84 ILLINOIS BIOLOGICAL MONOGRAPHS
of one to one and one-third times the least width of the ramus. The
terminal claw is approximate to one-half the length of the ventral margin
of the furca. The claws are stout and in most specimens are slightly
S-shaped, especially the subterminal claw (fig. 37-C). The genital lobe
is elongated, almost finger-like, and extends posteriorly between the furcal
rami (fig. 37-G).
Description of the Male: The shell of a mature male measured 1.20
mm. in length and 0.61 mm. in height. Sharpe (1897) gives the size as
1.25 mm. long and 0.63 mm. high. The single intact male shell of the
writer’s collections agrees with the description given by Sharpe: “‘the shell
of the male is much higher posteriorly, the greatest height being about
half the length; anterior extremity evenly rounded, narrow; posterior
sloping ventrally. Dorsal margin rather evenly rounded; ventral, deeply
sinuate anterior to the middle of the shell’? (Sharpe, 1897). As this
single mature male with the shell intact had been dead for some time, it
was impossible to secure from it any details of the appendages beyond
those given by Sharpe (1897). In another male, however, the appendages
were in such condition as to allow a comparison with the description
given by Sharpe. In addition to the observations given by Sharpe, the
writer found that the penis (fig. 38) is oval in shape and widened in the
center. The outer lobe is conspicuous; the two distal lobes small.
Besides differing in the shape and size of the shell, the male differs from
the female chiefly in the shape of the furca which is much straighter
and distally narrower in the male.
Remarks: While Sharpe based his original description of C. sigmoides
on male specimens and the present writer found only two mature males
for comparison, it is evident especially through the shape of the furcal
claws that the females seen by the writer belong to this species. One of
the mature male specimens occurred in a collection in which were two
mature females as well as several immature young males possibly also
belonging to this species, but too insufficiently developed to merit identi-
fication or description.
Ecology: Sharpe (1918) reports C. sigmoides from lake and river
shores. The present writer found it in algae hanging in the slow cur-
rent of a small permanent stream three feet wide and in water plants
along the edge of two small sluggish permanent streams.
Distribution: Sharpe (1897) collected his specimens of C. sigmoides
at Havana, Illinois, and Kofoid (1908) reported the species from the
same locality. The present writer has taken the species in Lake County
on June 29, 1940; in Tazewell County on August 29, 1940; and in Knox
County on June 14, 1940. This species has not been reported outside of
the State of Illinois.
OSTRACODS OF ILLINOIS—HOFF 85
Candona indigena sp. nov.
(Pl. III, fig. 39; pl. IV, figs. 40-48)
Type Locality: Illinois and Tennessee.
Description of the Female: A Candona species of the Acuminata
group. The holotype (fig. 39) in alcohol measured 1.08 mm. in length,
0.59 mm. in height, and 0.52 mm. in width. The width is little less than
90% of the height. Measurements of left valves of six females including
several paratypes as well as the holotype after mounting in diaphane
— Length Height
1.04 mm. 0.60 mm. (holotype)
0.96 0.56
0.97 0.58
0.96 0.55
1.00 0:55
1.10 0.65
The right valve (fig. 40) of the shell of the female is not as high as the
left, being usually 0.02 to 0.03 mm. less. The anterior margin of the shell
is somewhat evenly rounded, blending into the dorsal margin without
much conspicuous change in the arc. The highest part of the left shell
is at the beginning of the posterior one-fourth in most shells, slightly
anterior to this in a few individuals. At the beginning of the posterior
one-fourth, a very distinct angulation is formed by the curved dorsal
margin and the abruptly subtruncated posterior margin. The posterior-
ventral angulation approaches more a right angle than one of sixty degrees.
The ventral margin is slightly but distinctly sinuated ; the submarginal line
is relatively removed from both the posterior-ventral and the anterior-
ventral margins ; the pore-canals are very conspicuous, especially along the
anterior-ventral and the posterior-ventral margins. From above (fig. 42):
ovoid, slightly less pointed posteriorly than anteriorly; the left valve
slightly overlapping the right at both ends. The sides make a very even
and uninterrupted arc; widest in the area just behind the midpoint
and considerably posterior to the attachment place of the closing muscles.
Bristles of the dorsal posterior margin usually very long and heavy; finer
bristles at the ventral posterior margin and along the anterior margin.
The surface of the shell bears a few scattered puncta with hairs. The
muscle scars are subcentral, usually slightly ventral and anterior from
the center of the shell. There is normally a curved anterior row of four
scars with two additional scars just posterior to the ventral two of the
row. There may be two weak, separated scars ventral and anterior to
the group of six.
The antennules consist of eight podomeres; podomere three is dis-
tinctly wider than long; podomere four is slightly wider than long, being
86 ILLINOIS BIOLOGICAL MONOGRAPHS
much shorter than the more distal podomeres. Podomere five is one and
one-half times as long as wide. The ultimate (eight) and antepenultimate
(six) podomeres are equal in length to the fifth, while the length of
the penultimate podomere is one and one-half the length of the fifth.
Antennae of five podomeres in the female. Two of the claws of the
penultimate podomere are equal or subequal to the longest one of the
claws of the last podomere. The shorter terminal claw is six-sevenths or
seven-eighths as long as the other and extends beyond the shortest claw
of the penultimate podomere. The ultimate podomere is about three-
fifths as wide as long. The teeth of the chewing edge of the mandible
(fig. 43-C) are elongated, heavily chitinized, and distinctly separated
from each other even at the base. The palp is characteristic of the
Acuminata group with the seta of the medial side of the penultimate
podomere unfeathered and having a group of four setae (fig. 43-S) on
the inner margin of the antepenultimate podomere. The branchial plate
of the maxilla has twenty-four rays, the first five of which are directed
toward the mouth. One seta of the third maxillary process is larger than
the rest and not toothed.
The branchial plate (exopodite) of the first thoracic leg is reduced to
two setae. One of these is rather stout and over 60 p» long, the other is
weak and just a little more than one-fourth the length of the first. The
second thoracic leg (fig. 44) is composed of five podomeres. Near the
apical border of the second podomere is a seta approximately equal in
length to the width of the podomere. The length of the second podomere
is about equal to the sum of the lengths of the three more distal podo-
meres. The antepenultimate and penultimate podomeres are subequal in
length and each is about five-eighths as wide as long. Each of these
podomeres has a seta which is not quite equal in length to the podomere.
The penultimate podomere also has a very small seta whose base is near
the base of the larger one. The ultimate podomere is conical and tapers
evenly to the apical claw. One of the two apical setae is equal in length
to the apical podomere and the other is one-half as long. The apical claw
is equal in length roughly to one and one-fourth times the sum of the
last three podomeres of the appendage.
The third thoracic leg (fig. 45) clearly appears to be formed of five
podomeres. There are no setae on the second and the apparent antepen-
ultimate podomeres. The seta of the penultimate podomere and the
shortest seta of the ultimate podomere are not more than gently curved
and are not bent distally. In relation to the shortest seta of the apical
podomere, the companion seta is about two and one-fourth to two and
one-half times the shortest in length; while the oppositely directed seta
is only two to two and one-fourth times as long. The apical podomere
is about as long as wide,
OSTRACODS OF ILLINOIS—HOFF 87
The furcal ramus (fig. 46) of the female has a straight dorsal margin
and a slightly curved ventral margin. The ratio of the least width of the
base of the furca to the length of the ventral margin is about 1:9. The
dorsal seta is three and one-half times the least width of the base of the
furca and is removed from the subterminal claw by a distance more than
twice the least width of the ramus. The subterminal claw measures in
length nearly five times the width of the ramus; while the terminal claw
is about one-half of the length of the dorsal margin of the ramus. The
terminal seta is small, measuring about one and one-half times the least
width of the ramus. Both claws are curved at the tips, rather slender,
and are toothed especially in the middle third. The female sexual lobe
(fig. 46-G) is moderately developed, being in the form of a narrow cone
or papilla extending finger-like between the furcal rami but usually not
beyond the dorsal margin of the rami. The ventral margin of this lobe is
somewhat concave, while the dorsal margin is nearly straight.
Description of the Male: The shell of the male is nearly like that of .
the female when viewed from above. From the side (fig. 41), however,
the ventral margin is usually more concave and the posterior margin is
more rounded with a less conspicuous posterior-ventral point. The allotype
measured 1.08 mm. long, 0.61 mm. high, and 0.54 mm. wide in alcohol.
Measurements of the left valve of two males mounted in diaphane are as
follows:
Length Height
1.04 mm. 0.59 mm. (allotype)
1.04 0.60 (paratype)
The appendages of the male differ little from those of the female.
The antenna has six podomeres but the end claws are very similar to
those of the female. The prehensile palps of the first thoracic leg are
dissimilar and unequal, the left (fig. 47b) being longer than the right
(fig. 47a). Both are slightly curved distally and each has a distal seta
and a medial one. The medial one is located more than one-third of
the distance from the distal end of the left palp, less than one-third of
the distance in the right palp. The penis (fig. 48) is widened distally
and the outer lobe is unequally bilobed (fig. 48-O).
Remarks: Although the shell in this species is slightly higher than
one-half of the length, there can be little doubt that it is distinctly a
member of the Acuminata group. This species not only possesses the
characters recognized as belonging to members of the group Acuminata
but it also bears a close resemblance to some of the European members
assigned to the Acuminata group. The posterior margin of the shell is
oblique or truncate and shows a posterior-ventral angle similar to
C. levanderi Hirschmann 1912 (Hirschmann, 1912), and C. lapponica
88 ILLINOIS BIOLOGICAL MONOGRAPHS
Ekman 1908 (Sars, 1928) from Europe. In size C. indigena is larger than
C. lapponica but a little smaller than C. Jevandert.
Ecology: Candona indigena is an inhabitant of temporary ponds where
it seems to be well adapted to living in masses of decaying leaves and
vegetation on otherwise more or less bare bottom in rather shallow water.
As this species is distinctly an inhabitant of temporary ponds and sloughs,
it is taken only during the vernal season.
Distribution: This species has been taken in three collections from
east central Illinois: two collections from Seymour Prairie, Champaign
County, on April 15, 1940, and one from Busey’s Pasture, Urbana,
Champaign County, on the same date. Two individuals were collected
near Congerville, Woodford County, on May 28, 1940, and a few indi-
viduals of this species were found in a collection made by Robert Yapp
from a slough near Reelfoot Lake, Tennessee, on March 22, 1940.
The holotype (female) and allotype (male) of this species are de-
posited in the U. S. National Museum (Cat. Nos. 81070 and 81071).
Paratypes are in the collections of Dr. H. J. Van Cleave, Dr. Arthur G.
Humes, and the writer.
Candona suburbana sp. nov.
(Pl. IV, figs. 49-54; pl. V, figs. 55-57)
(?) Mea eda elongata Herrick 1879 sp. indet. Herrick, 1879:113, pl. 20, figs. 2, 2a,
lb (&
Type Locality: Busey’s Pasture, Urbana, Champaign County, Illinois.
Description of the Female: A Candona species belonging to the
Acuminata group. The shell (fig. 49) of the single female (allotype)
examined is elongated, over twice as long as high. After mounting in
diaphane, the right valve measures 1.04 mm. in length and 0.47 mm. in
height; the left valve, being considerably larger, measures 1.08 mm. in
length and 0.51 mm. in height. The width is about four-fifths of the
height. The ventral margin has a sinuation in the posterior part of the
anterior one-half of the shell; the anterior end is slightly more evenly
and broadly rounded than the posterior end. In the left valve, the dorsal
margin is nearly evenly rounded, passing more or less insensibly into the
anterior and posterior margins although a very slight sinuation is indi-
cated in the dorsal margin and between the dorsal and anterior margins.
In the right valve, on the other hand, the sinuation of the dorsal margin
and those between the dorsal and anterior and dorsal and posterior
margins are more evident.
The surface of the shell bears a considerable number of short, weak
hairs each of which is set on a well marked papilla. The hairs of the
anterior and posterior margins are few in number and are weakly de-
OSTRACODS OF ILLINOIS—HOFF 89
veloped. Pore-canals are conspicuous at both ends as well as along the
ventral margin. The muscle scars are somewhat anterior of the center of
the shell and are very definite in arrangement. There are five scars
forming a rosette with a single isolated one above the group and two
isolated scars slightly anterior-ventral to the rosette.
The distal five podomeres of the antennules become regularly longer
and narrower distally; the fifth and sixth podomeres have an outer seta
longer than the length of the next podomere; the fifth, sixth, and seventh
podomeres each has two long medial swimming setae. Distally, the
eighth podomere bears two setae longer than one and one-half times the
length of the podomere, one seta about half again as long as the short ones,
and a very long swimming seta. The antennae have a group of four setae
on the distal one-third of the penultimate podomere ; the longest distal claw
extends but little if any beyond the longest claw of the penultimate
podomere. The medial distal seta of the penultimate podomere of the
mandibular palp is smooth; there are four setae in the group on the
antepenultimate podomere. The mandibular teeth consist of five very
heavy teeth and two or three small, rudimentary teeth. Of the twenty-
two rays in the branchial plate of the maxilla, four are directed orally.
The second leg (fig. 52) has the second podomere almost equal in
length to the sum of the lengths of the third and fourth podomeres. The
second podomere bears a distal seta shorter than the distal width of
the podomere. The third and fourth podomeres are approximate in
length with the distal seta of each, about equal in length to the length of
the ultimate podomere of the appendage. The ultimate podomere is
nearly twice as long as wide and bears distally a short seta about equal
in length to the podomere, another three-fourths as long, and a claw
slightly subequal in length to the sum of the lengths of the distal three
podomeres of the appendage. The third thoracic leg appears to be formed
of five podomeres through the division of the penultimate. The basal
podomere bears two seta. The apparent second and third podomeres
seem to bear no setae; the seta of the penultimate podomere is longer
than the length of the podomere. The ultimate podomere is nearly
square. The length of the shortest distal seta is four times the length
of the ultimate podomere and is about one-half the length of the longer
companion seta. The oppositely directed seta has a length about two times
that of the shorter seta of the pair.
The furcal rami are nearly straight. The length of the ventral margin
of the ramus is about eleven times the least width; the length of the
dorsal seta is three and one-half to nearly four times the least width of
the ramus and is located about one-third of the length of the dorsal
margin from the distal end of the ramus. The finely toothed terminal
90 ILLINOIS BIOLOGICAL MONOGRAPHS
claw is about one-half as long as the ramus. The length of the terminal
seta is about one and one-half times the least width of the ramus. The
genital lobe (fig. 54-G) is moderately well developed, being triangular and
lacking the long finger-like projection often seen in members of the
Acuminata group. The genital lobes do not extend beyond the dorsal
margin of the furcal rami.
Description of the Male: The shell (fig. 50) of the male is slightly
larger than that of the female. Measurements of valves mounted in dia-
phane are as follows:
RIGHT LEFT
Length Height Length Height
1.00 mm. 0.— mm. 1.12 mm. 0.56 mm. (holotype)
1.13 0.55 1.16 0.58
2 0.52 1.16 0.54
The ventral margin is much more deeply sinuated than in the female
shell. The dorsal margin, as a rule, is regularly and evenly arched and
passes insensibly into the anterior and posterior margins. There are
no evidences of sinuations in the center or at the ends of the dorsal
margin except a slight dorsal flattening, which occurs in a few valves.
A dorsal view (fig. 51) of the shell shows the sides to be rather evenly
rounded and the ends somewhat pointed, the anterior more so than the
posterior.
The antennules, mandibles, and maxillae are similar to those of the
female. The antennae are slightly different in having lost the group of
four setae on the penultimate podomere and in having acquired the
customary heavy male seta at the distal end of the antepenultimate
podomere. The second thoracic leg of the male differs from that observed
in the female as follows: the second podomere is almost equal in length
to the sum of the lengths of the three distal podomeres, the third podo-
mere is slightly longer than the fourth, the seta of the third podomere
is a little longer than in the female, and the terminal claw is slightly
longer in relation to the length of the ultimate podomere. As the descrip-
tion of the female is based upon a single specimen, it is difficult to de-
termine whether or not the slight differences between male and female
appendages are the result of individual variation or are sexual differ-
ences. The third thoracic leg of the male (fig. 53) is essentially like that
of the female.
The furca (fig. 55) of the male is more slender than the furca of the
female and somewhat curved so that the ventral or anterior margin is
slightly convex. The length of the ventral margin is nearly fourteen
times the least width of the furcal ramus. The dorsal seta is located one-
third of the length of the dorsal margin from the distal end of the furca.
OSTRACODS OF ILLINOIS—HOFF 91
The length of the dorsal seta is over four times the least width of the
ramus, being about one-half as long as the terminal claw which, in turn,
is about one-half as long as the ventral margin of the furcal ramus. The
length of the terminal seta is twice the least width of the ramus. There
is a very slight tendency in some instances to have an S-curvature in the
terminal claw and more especially in the subterminal claw. This curvature
is not pronounced.
The prehensile palps are unequal and somewhat similar; the right
(fig. 56b) being rather large and stout, the left (fig. 56a) smaller and
with a widening at the distal end. The penis (fig. 57) is oval in general
outline, with prominent outer lobe (fig. 57-O).
Remarks: Because of the number of both American and European
species belonging to the group Acuminata, it is difficult to establish a
definite relationship between C. suburbana sp. nov. and other described
species. Four species described by Furtos (1933) seem to be related to
C. suburbana, at least superficially. However, it is impossible to ascertain
from the descriptions given by Furtos that her species belong to the group
Acuminata because that writer fails to give many of the characteristics
necessary for assignment of particular species to the proper group. These
possibly related species and the ways in which they differ from C. subur-
bana are as follows: (1) C. suburbana differs from C. eriensis Furtos
1933 in the undivided penultimate podomere of the third leg of the latter ;
the penis is wider; the shell has a conspicuous posterior-dorsal angulation
and shows only six muscle scars. (2) C. suburbana differs from C.
scopulosa Furtos 1933 in shell shape and in the unclear division of the
penultimate podomere of the third thoracic leg in the latter form. The
female genital lobe is much longer, the prehensile palps more curved, and
the penis wider in C. scopulosa. (3) C. decora Furtos 1933 differs from
C. suburbana in having the shell larger with a well angulated dorso-
posterior margin. C. decora also has a much longer female genital lobe.
(4) C. distincta Furtos 1933 differs from the new species by a well
marked angulation and sinuation near the point where the posterior and
dorsal margins of the shell meet. In a view from above, the fairly well
rounded ends of the shell of C. distincta are in contradiction to the more
pointed ends of C. suburbana. Other differences also occur. C. suburbana
is also related to several species of Candona from Illinois. A comparison
of these species with C. suburbana is given under the “remarks’’ in the
description of C. acuta and needs not be repeated.
It is possible that C. suburbana may be the C. elongata described by
Herrick (1879). Herrick’s description is so incomplete and his figures
so poor that it is impossible to make out with certainty just what species
he actually collected. G. W. Miller (1912) through a gross error thoug"t
92 ILLINOIS BIOLOGICAL MONOGRAPHS
that C. caudata Kaufmann 1900 was a synonym of C. elongata Herrick
1879 and took the name given by Herrick to be the valid name. Since
then, Klie (1938a) and others have realized Miuller’s mistake and have
rejected the name C. elongata Herrick. It is very obvious that C. elongata
Herrick is not the same ostracod as C. caudata Kaufmann, as may be
readily seen in a comparison of the shell of the two forms. While there
is a remote possibility that C. suburbana and C. elongata might be the
same, it is impossible to determine this with certainty on the basis of
Herrick’s inadequate description. In Herrick’s figures (pl. 20, figs. 2, 2a,
b, c) the shape of the shell, form of the antennae, and form of the pre-
hensile palps indicate a Candona, but, at the same time, some of the setae
are lacking from the third thoracic leg, the antennules have too few
podomeres, and the ejaculatory duct is too much shortened for a Candona.
If Herrick, who stated that he did not know whether the species is a
Candona or a Cypris species, could not properly place the species in the
genus and could not give figures which would make possible definite
determination of the genus, certainly it is not safe to use his specific
determination. To the present writer, it seems inadvisable to accept
Herrick’s name in view of the fact that his description and figures are so
inadequate. If the type locality of C. elongata Herrick were known, it
might be possible to secure topotypes and clear the situation, but the type
locality is nowhere mentioned by Herrick.
Ecology: C. suburbana sp. nov. was taken from a temporary pond
(ox-bow) which usually dries up at least by the serotinal season. The
collections were made by dragging a plankton net in the grass along the
edge of the pond where the water was from three to six inches deep.
The water was clear and some algae were present.
Distribution: The writer has taken C. suburbana in only two collec-
tions from pond No. 2, Busey’s Pasture, on the north outskirts of Urbana,
Illinois. On May 22, 1940, eight mature males were taken and on June 9,
1940, a single mature female was obtained. Several previous and later
collections from the same pond contained no individuals of this species.
The holotype (male) and the allotype (female) are deposited in the
U. S. National Museum (Cat. Nos. 81073 and 81072). Paratypes (male)
are in the collections of Dr. H. J. Van Cleave and the writer.
Candona fossulensis sp. nov.
(Pl. V, figs. 58-64)
Type Locality: Champaign County, Illinois.
Description of the female: A Candona of the Acuminata group. The
shell has a height of more than one-half the length and is highest near the
beginning of the posterior third. The left valve (fig. 58) has a slightly
OSTRACODS OF ILLINOIS—HOFF 93
convex dorsal margin with a weak sinuation at the junction of the dorsal
and anterior margins. The anterior end is evenly and narrowly rounded.
The posterior end is broadly rounded, appearing subtruncate and having
the union of the dorsal and posterior margins marked by an angulation.
The ventral margin is flatly concave with the concavity deepest near the
center of the margin. The right valve is very similar in shape to the left
with the exception that the sinuation between the dorsal and anterior
margins is much more pronounced. The left valve is slightly larger than
the right. The width of the shell is considerably less than the height.
Measurements of the length and height of valves mounted in diaphane
are as follows:
RIGHT LEFT
Length Height Length Height
0.99 mm. 0.52 mm. 1.00 mm. 0.54 mm. (holotype)
1.00 0.52 02 0.54
1.04 0.55 1.06 0.57
The shell margins exhibit many fine hairs especially at the anterior and
posterior ends. Because of the proximity of the submarginal line and the
valve margin, the pore-canals are obliterated except along the ventral
margin in an area just anterior to the ventral sinuation. There is a rosette
of five muscle scars with a single scar just above the rosette. This rosette
is placed anterior to the center of the valve. A short distance ventral and
anterior are two additional small, well-separated scars and some distance
anterior and dorsal of the group are two more very small isolated scars.
Posteriorly the shell has very peculiar markings (fig. 59) which divide
the surface of the shell into irregular square and diamond-shaped areas.
This sculpturing is conspicuous anterior to the posterior margin in an area
which might be called the posterior slope. The markings cannot be ob-
served in the anterior four-fifths of the shell.
The antennules and antennae are slender with the swimming setae
of the former and the claws of the latter long and slender. The distal
podomere of the antennules is nearly six times as long as wide; the fourth
podomere is about as long as wide, and the more distal ones are all
cylindrical. The terminal claws of the antennae reach to the level of the
tips of the longest claws of the penultimate podomere. The penultimate
podomere is well over twice as long as wide. The length of the sensory
bristle of the antepenultimate podomere is less than the width of the
podomere. The two distal podomeres of each mandibular palp (fig. 60)
are more slender than in many Candona; the medial distal seta of the
penultimate podomere is smooth, and the bundle on the antepenultimate
podomere consists of four setae (fig. 60-S). The two terminal claws of
the mandibular palp are short and heavy.
The second thoracic leg has the second podomere nearly equal in
length to the sum of the lengths of the three distal podomeres and equal
94 ILLINOIS BIOLOGICAL MONOGRAPHS
in length to the distal claw of the appendage. The apparent penultimate
and antepenultimate podomeres are equal in length; the length of the
ultimate podomere is approximate to one-half the length of the penulti-
mate. The ultimate podomere is longer than wide. The seta of the penulti-
mate podomere is approximately three-fourths as long as the length of
the podomere; the seta of the antepenultimate podomere is equal to the
seta of the penultimate while the seta of the second podomere is usually
slightly shorter. Considerable variation occurs in the relative lengths of
the setae of the second leg. The basal podomere of the third thoracic
leg (fig. 61) bears two setae. The penultimate podomere is divided; the
ultimate podomere is as wide as long. The shortest distal seta is four
times as long as the width of the ultimate podomere; the companion seta
is a little less, and the oppositely directed seta a little more, than twice
as long as the shortest distal seta.
The furca (fig. 62) is gently curved; the length of the ventral margin
is nine times the least width of the ramus. The dorsal seta has a length
equal to three or three and one-half or in some individuals nearly four
times the least width of the furcal ramus. The dorsal seta is located a
distance from the subterminal claw usually equal to a little more than
three times the least width of the furca. The length of the terminal claw
is a little less than one-half the dorsal margin of the furcal ramus. The
length of the terminal seta is equal to the least width of the furcal ramus.
The genital lobe (fig. 62) consists of a long finger-like projection attached
to the dorsal-posterior margin of a large hemispherical base. The finger-
like lobe has a concave, sometimes almost straight but never convex,
dorsal edge and a convex ventral edge. The lobe is often distally bent
dorsad.
Description of the Male: The shell of the male is similar to that of
the female but slightly larger. The ventral sinuation of the shell of the
male is more pronounced and somewhat anterior to the center of the
ventral margin. Measurements of the valves of three males are as fol-
lows (mounted in diaphane) :
RIGHT LEFT
Length Height Length Height
1.12 mm.) 0.60°mm- 1.13 mm. 0.61 mm. (allotype)
1.18 0.62 1.20 0.64
1417 0.59 1.19 0.—
The cephalic and thoracic appendages of the male resemble those of the
female with the exception that the second thoracic legs are more slender.
The furca of the male is more slender than that of the female; the
length of the ventral margin is from twelve to thirteen times the least
width. Because of the slender condition of the distal end of the furcal
OSTRACODS OF ILLINOIS—HOFF 95
ramus, the dorsal seta has a length over four times the least width of the
ramus and the length of the terminal seta is one and one-half times the
least width of the ramus. The terminal claw has a length equal to about
two-fifths of the dorsal margin of the ramus. The prehensile palps are
dissimilar and somewhat unequal. The right (fig. 63a) is heavy and falci-
form; the left (fig. 63b) is less stout, and the tip extends straight without
change in diameter for some distance distal of the bend of the palp. The
penis (fig. 64) is wide and rather short; the middle and inner lobes are
not well developed and do not extend beyond the penis proper; the outer
lobe appears as a lappet with what appears to be a tubule ending at the
margin a short distance dorsal to the tip of the lobe.
Remarks: Of all the described species of Candona, C. decora Furtos
1933 seems to be the most closely related to C. fossulensis sp. nov. That
the two species are related is shown by the agreement of the two species
in general shell shape and sculpturing and in the similarity of the penis
and prehensile claws. The characteristics in which C. fossulensis sp. nov.
and C. decora Furtos differ may be listed as follows:
C. decora Furtos 1933 C. fossulensis sp. nov.
Female, size of shell................. 1.18-1.30 x 0.63-0.70 1.00-1.05 x 0.54-0.57
Malewsizevot Shelli’ 05 ibs cee ee 1.4-1.5 x 0.7-0.8 1.12-1.2 x 0.60-0.64
Dorsal-posterior angulation........... More Less
Female: 3rd leg, last podomere....... Length more than width Length equals width
OTE SR ic [rr 314 x last podomere 4 x last podomere
Purea; ventral margin............0.. 13 x least width 9 x least width
Intireas dorsal seta... .20s0sc4 0s 05 sales 7% of subterminal claw 54 or 4% of sub-
terminal claw
Hinted dorsal seta... <0. eos 6 0 esses ¥, from distal end of ¥ from distal end of
ramus ramus
A comparison of the characters of C. fossulensis with related Acuminata
species from Illinois is given under C. acuta described herein.
Ecology: The type specimens were taken from a roadside ditch in
which the water was three inches deep and the bottom was covered with
dead grass. Another collection was made on the same date in a nearby
vernal pond in which the water was up to twelve inches deep and there
was little dead grass on the bottom.
Distribution: C. fossulensis sp. nov. has been taken in only two col-
lections. These were from separate bodies of water in the same vicinity
near Seymour, Champaign County, Illinois. The two collections were
made on April 1, 1940.
The holotype (female) and allotype (male) of C. fossulensis are
deposited in the U. S. National Museum (Cat. Nos. 81068 and 81069).
Paratypes (female and male) are in the collections of Dr. H. J. Van
Cleave, Dr. Arthur G. Humes, and the writer.
96 ILLINOIS BIOLOGICAL MONOGRAPHS
Candona acuta sp. nov.
(Pl. V, figs. 65-69; pl. VI, figs. 70-72)
Type Locality: Illinois.
Description of the Female: A Candona of the Acuminata group with
the shell height and width approximating one-half of the shell length.
The dorsal margin is flatly arched (fig. 65) ; the anterior end is narrowly
and evenly rounded, a definite sinuation separating anterior and dorsal
margins. The ventral margin has a very conspicuous sinuation slightly
anterior to the mid-point, with the margin between the sinuation and the
posterior-ventral angulation flattened. The posterior end has a bluntly
rounded, subtruncate margin. The posterior and ventral margins join at
nearly a right angle in the right valve. There is a very slight sinuation
between the dorsal and posterior margins but this is more apparent than
real as it is caused largely by the extension of the valve beyond the
posterior shell margin. The ovary appears as a narrow band, posteriorly
much more narrowed than in most Candona. The muscle scars con-
sistently occur in a greater number than in many Candona as there is a
nearly centrally located rosette of five loosely arranged scars, a single
scar slightly more dorsad, two scars some distance anterior-ventrad,
and two smaller scars anterior-dorsad of the rosette. The submarginal
line is close to the margin of the valves so that the pore-canals are
very short. The surface of the shell bears a few scattered hairs which
are fairly conspicuous along the margins. From below (fig. 66), the
sides of the shell form an even arc with the anterior slightly more pointed
than the posterior.
The right valve of the holotype measures 1.07 mm. in length, 0.54
mm. in height, and 0.56 mm. in width. Measurements of the valves of
other mature females (paratypes) are as follows (mounted in diaphane) :
RIGHT LEFT
Length Height Length Height
1.06mm. 0.53 mm. 1.10 mm: 0:56 nmr
1.05 0.54 1.09 0.56
1.08 0.55 ls 0.58
The antennules show few characteristics helpful in specific diagnosis. The
fifth, seventh, and eighth podomeres are equal in length; the sixth is
slightly shorter. The antennae are short and stout; the terminal claws are
very heavy and not proportionally as long as in many Candona. The
longest claw of the penultimate podomere extends beyond the longest claw
of the ultimate podomere. The penultimate podomere bears submedially
a group of four small setae near the distal end of the podomere. The
sensory organ of the antepenultimate podomere is much reduced, being
OSTRACODS OF ILLINOIS—HOFF 97
little more than one-half as long as the width of the podomere at the
same level.
The medial-distal seta of the penultimate podomere of the mandibular
palp is smooth; the bundle of setae on the antepenultimate podomere
contains four setae. The second thoracic leg (fig. 67) has the length
of the second podomere equal to the sum of the lengths of the distal three
podomeres. The penultimate (fig. 67-P) is hardly as long as the ante-
penultimate podomere; the seta of the antepenultimate podomere reaches
to the base of the seta of the penultimate and is not as long as the seta
of the penultimate. The ultimate podomere is longer than wide and,
besides the claw, bears a distal seta longer than the podomere and a sub-
distal seta equal to the length of the podomere. The terminal claw is
usually a little longer than the sum of the lengths of the last three
podomeres and is commonly recurved toward the distal end. The sides
of the second, third, and fourth podomeres bear small spines.
The third thoracic leg (fig. 68) consists of five apparent podomeres
through the division of the penultimate podomere (fig. 68-P). The basal
podomere has two setae, both of which are long. The seta of the penulti-
mate podomere is sometimes bent near the distal end and is very long;
being approximate to the short seta of the ultimate podomere, it has a
length equal to the sum of the length of the apparent antepenultimate
and penultimate podomeres. There are a few very short spines along the
sides of the penultimate podomere. The ultimate podomere is little longer
than wide. The shortest of the three distal setae is nearly four times the
length of the ultimate podomere; the companion seta is about twice as
long as the shorter; the length of the oppositely directed seta is variable,
either sub-equal or equal to the longer one of the pair and, like the
shortest distal seta, is distinctly bent near the distal end.
The furcal ramus (fig. 69-R) is somewhat curved; the length of the
ventral margin is ten times the least width. The dorsal seta (fig. 69-D)
has a length of two and one-half times the least width of the ramus and
is removed from the subterminal claw by a distance equal to a little less
than one-third of the ventral margin. The length of the terminal seta is
one and one-fourth times the least width of the furcal ramus. The claws
are gently curved throughout their length; the length of the terminal claw
is approximate to one-half of the length of the ventral margin of the
furcal ramus. The claws are very finely toothed. The female genital
lobe (fig. 69-G) is well developed, bluntly pointed at the posterior end,
and separated from the thorax by a slight constriction. There is a seta
(fig. 69-B) on the dorsal portion of the thorax near the base of the furca.
Description of the Male: The shell (fig. 70) of the male differs con-
siderably from that of the female. The posterior end is broadly rounded,
ILLINOIS BIOLOGICAL MONOGRAPHS
98
UO01}911}SUOD
e Aq xeioy}
WO1} pazeiedas
snulel jo
YIPIM ysea]
sown HI
snuiel Jo
YIPIM yseay
soul} 347
snwel jo
YIPIM ysva]
SOW} 01-6
SoJoUl
-opod 9014}
[eqsip sjenby
DATPA IYSII
ul UOT}E/Nsuy
PIUESS'0-9Si0
WU eT T-OFT
uo1dealoid
suo] ‘aseq
jeoeydsiwayzy
snurei Jo
HADES asee]
se dues
snured jo
YIPIM 4sea]
sou} 34 E-¢
SNuIeI JO
HES SEs
SOUIT} 6
salaulopod
9914} [e}
-sIp jo wins
sjenba AjreaNy
pepunoy
cau /S°0-75'0
Wed T-00'T
‘nou “ds
sisuanssof *D
Je[nsuels zy,
snuied jo
YIPIM yseay
sowing 34]
snurel jo
YIPIM sea]
sour) 7-34 ¢
snurel jo
YIPIM 4se9]
sou} T]
so10Ul
-opod 9a14}
[ESE ID EO.
uns uey} ssa]
pepunoy
“aou ‘ds
puDgangns *D
axl [-Jesuy
‘MOIIE N
snurer jo
YIPIM ysea]
Sout 34]
snures Jo
YIPIM 4sea]
soumny 4¢
snuiel jo
YIPIM 4sea]
SOUT} 6
soioUul
-opod 9914}
[eIsIp souwity
MI syenby
a[sue spiM
“wut ¢9°0-SS'0
“Wt QT T-S6'0
“nou ‘ds
DuasipUur “JD
oy t]-TesULy
snulelr jo
YIPIM yseay
soul} 4] -T
snwed jo
YIPIM yseo]
sou HE
snured jo
YIPIM ysea]
soul} 546-6
sa1dul
-opod 3914}
[eqsip spenby
DA[CA 32]
Ul uOTWeNsuy
wu ¢<"0
ORION
L681 adieys
saplomsis “9D
au0d Zuo]
Ajeyeraposyy
snwel jo
YIPIM qseay
SB QUIeS
snuret jo
eo
SoUII} Z
snuiei jo
YIPIM ISea]
soulty TT
so1OUl
-opod 9014}
[eqsip sjenby
BAILA 32]
ul uoT}yejnsuy
“um ¢9°0-08°0
WU Se r-St th
006, UUeWjNesy
DIDPNDI *D
‘JENPIAIpul v[Zurs @ uo paseq SJusWeINseIW,
aqo] [e}1ues ajeuay
Bas [CUIUIII} JO Y}3uaT
eyes [esIop Jo y}ZuaT
uls1ew
]e4qU9A jo yy3UaT
—:e0IN J
39] puodes
JO MeID [e}SIP JO 4yBuaT
SUISIVUI [eI]USA
pure 10110}sod jo uonounf
7YSI9q [14S
4ya3ugy [24S
SIONITT[ NI GNNOY SV dNOUds) VIVNINNOY AHL dO SHIDNdS GHLVTAY ATASOTD ANOS AO NOSIYVdWO7)
OSTRACODS OF ILLINOIS—HOFF — 99
the anterior narrowly rounded. The dorsal margin is relatively uninter-
rupted and passes as an arc from the posterior to the anterior margins.
The ventral margin is deeply sinuated, the sinuation being followed pos-
teriorly by a flattened area along the ventral margin. In some shells, there
is a slight angulation at the juncture of the posterior and dorsal margins
and a slight sinuation at the beginning of the anterior margin. Measure-
ments of the valves of several males (mounted in diaphane) are as
follows:
RIGHT LEFT
Length Height Length Height
1.24 mm. 0.62 mm. 1.28 mm. 0.64 mm. (allotype)
1.19 0.59 1:22 0.62
1,26 0.64 1:31 0.69
The antennules and antennae are essentially like those of the female
except for the presence of the male setae and the loss of the group of
four small setae already mentioned. The second thoracic leg is like that
of the female except in some males the entire appendage has a tendency
to be slightly more slender with the terminal claw proportionally longer
and often not recurved near the distal end. The third thoracic leg is
similar to that of the female. In the furca, the ramus between the base
of the dorsal seta and the subterminal claw is very narrow. This results
in the length of the ventral margin being about fifteen times the least
width of the ramus. The narrowed portion of the ramus is strongly
curved. As a result of the narrowness of the furca, the dorsal seta has
a length of about four and one-half times the least width and the terminal
seta is nearly twice as long as the ramus is wide.
The prehensile palps are unequal and dissimilar. The left (fig. 7la)
has a very long, straight, and narrowed distal portion; the right (fig. 71b)
is falciform, shorter, and stouter than the left. Considerable variation is
shown in the prehensile palps, especially in the left where the degree of
relative narrowness and length is often different from that shown in the
pictured paratype. The penis (fig. 72) is elongated, the outer lobe
(fig. 72-O) well developed and the other two lobes small and poorly
developed.
Remarks: A tabular comparison of C. acuta with closely related
species of the Acuminata group as found in Illinois is given herewith.
(The chart compares females only.)
Ecology: Most collections of C. acuta sp. nov. have been made in grass
and decaying vegetation along the edges of small streams, usually tempo-
rary, three to eight feet wide, and up to two feet deep, where the water
is clear and cool and there is considerable current. In one instance, the
species was taken from a pond connected to a small stream only during
high water stages and, in another instance, from the stomach of a fish,
100 ILLINOIS BIOLOGICAL MONOGRAPHS
Catostomus commersonu, from the stripland ponds near Oakwood, IIli-
nois. The species seems not to be restricted to any season, having been
taken in May, July, and November.
Distribution: C. acuta sp. nov. has been taken from Champaign
County, Livingston County, and Vermilion County, Illinois. The species
seems to be restricted to the cooler waters of the state and has not been
collected from the southern part of the state. It has not been reported
outside of Illinois.
The holotype (female), allotype (male), and two paratypes (one
female, one male) are deposited in the U. S. National Museum (Cat.
Nos. 81074, 81075, 81076, and 81077). Other paratypes (both female and
male) are in the collections of Dr. H. J. Van Cleave, Dr. Arthur G.
Humes, and the writer.
Group Fabaeformis
The group of setae on the antepenultimate podomere of the mandibu-
lar palp consists of three or five setae. Characters otherwise as in the
group Acuminata.
Upon the basis of present information, it is impossible to assign any
Illinois species definitely to the group Fabaeformis. C. sharpei sp. nov.
may belong here, especially as this species was formerly assigned to the
European species C. fabaeformis Fischer 1851 by Sharpe (1897, 1918).
However, the inadequate available description seems to point to the
placement of this species in the group Acuminata. As a result, C. sharpet
sp. nov. has been tentatively assigned to the group Acuminata but may be
reassigned when more details of its structure become known.
SUBEA MILEY CY CLOCYPRINAE
Shell usually short and high, more or less rounded (figs. 76, 98).
Swimming setae of the antennae well developed (fig. 76-A) but occasion-
ally reduced; usually twice as long as the distance from their origin to
the tips of the terminal claws of the antennae. Antenna in female of
five, in male of six podomeres through a division of the penultimate
podomere. The first thoracic leg with well developed respiratory plate;
the palp (endopodite) in the female consists of one or two podomeres ;
in the male it is modified as a grasping palp or prehensile palp of two
podomeres (fig. 80). The distal podomere of each palp forms a movable
finger called the dactylus (fig. 80a-D) and rests on the proximal podo-
mere which is designated as the propodus (fig. 80b-P). Third thoracic
leg with three distal setae (figs. 84, 91), of which one is long and reflexed,
the other two are much shorter and not reflexed in most species. Ductus
OSTRACODS OF ILLINOIS—HOFF 101
ejaculatorius (fig. 93) with the proximal extremity of the tubule forming
a dilated pouch, the distal end forming a funnel-shaped sac leading into
the vas deferens.
The subfamily Cyclocyprinae replaces as a taxonomic unit the sub-
family Cyclocypridinae used by Sharpe (1903, 1918). Many writers, as
Furtos (1933), prefer to group the genera belonging to the Candoninae
and Cyclocyprinae into the subfamily Candocyprinae, which is then sub-
divided into tribes of less than subfamily and more than generic impor-
tance. The tribe Cyclocyprini is used by Furtos (1933, 1935) as an equiva-
lent to the subfamily Cyclocyprinae as used herein. To the present writer,
it seems desirable to avoid the use of such subdivisions as tribes which
tend to complicate the system of classification without introducing any
real advantage not gained by a simpler system.
As found in Illinois, the subfamily Cyclocyprinae includes three
genera: Cyclocypris Brady and Norman 1889, Cypria Zenker 1854, and
Physocypria Vavra 1897. A fourth American genus, Candocypria Furtos
1933, is found in Ohio but has not been discovered in Illinois.
KEY TO GENERA OF THE SUBFAMILY CYCLOCYPRINAE IN ILLINOIS
la. Shell tumid; the last podomere of the third thoracic leg at least twice as
fonerasmwide (fie: 75)\s. occ. .0scne Genus CycLocypris Brady and Norman 1889
b. Shell compressed; the last podomere of the third thoracic leg not much
Loic etumt atta G CM (CO Srw. O45 9100 care iotere wlcnevauseare ayer steate re cieitaciei tls MoM eo atten ee weet 2
2a. Valves nearly equal, margin of both valves smooth (fig. 76)..............
Ieee SE Gro echo nian wi dre site eve Siege Genus Cyprta Zenker 1854
b. Valves commonly unequal in height or length or both; margin of either
right or left valve more or less tuberculated (fig. 98)............0000eeeees
Ean yh SEN ko sarod was Har Seok cbse Hs Genus PHysocypria Vavra 1897
Genus CYCLOCYPRIS Brapy anp NorMaAn 1889
Shell rounded, height and width greater than one-half the length
(fig. 73) ; surface of shell smooth, brown in color. Eye well developed.
Swimming setae of both antennules and antennae are long and well
adapted for swimming. The penultimate podomere of the second
antenna in the male is divided, but no specialized male setae are present.
Respiratory plate of the first thoracic leg with six plumose setae. Third
thoracic leg consisting of four podomeres (fig. 75); the ultimate podo-
mere elongated, more than twice as long as wide and usually at least one-
half as long as the penultimate podomere. Ultimate podomere of third
leg with three distal setae, unequal, with the outermost one very long and
reflexed. The dorsal setae of the furca often greatly reduced and usually
removed some distance from the subterminal claw.
102 ILLINOIS BIOLOGICAL MONOGRAPHS
KEY TO SPECIES OF THE GENUS CYCLOCYPRIS IN IEERINGIS
la. Shell less than 0.5 mm. in length; terminal seta of the furca at least three-
fourths as long as the terminal claw; dorsal seta of furcal ramus absent
GL MMGUIMENTALY, ucidcis ss skorercoreolee aaa fae Coe ai a eee C. sharpei Furtos 1933
b. Shell over 0.5 mm. in length; terminal seta of furca not over one-half as
long as the terminal claw; dorsal seta of furcal ramus present............
SS EM aa at Sb His bi RAMS oa a aoe oer eee C. forbesi Sharpe 1897
Cyclocypris forbesi Sharpe 1897
(Pl. VI, figs. 73-75)
Cyclocypris forbesi Sharpe 1897. Sharpe, 1897:432-433, pl. 41, figs. 1-7; 1918:822,
figs. 1290a, b, c, d, e, £; Furtos, 1935:535-537, fig. 3.
Type Locality: McLean County, Illinois.
Description of the Female: An ostracod of the genus Cyclocypris.
According to Sharpe (1897), the shell measures 0.55 mm. in length,
0.39 mm. in height, and 0.36 mm. in width. The single female individual
observed in the present writer’s collection was slightly larger, measuring
0.62 mm. in length and 0.47 mm. in height. The shell (fig. 73) is plump
with the right valve slightly larger than the left. The height is almost
equal to three-fourths of the length. The color of the shell is a sepia
brown and there are occasional hairs especially along the margins. The
shell is subelliptical with the dorsal margin arched. The posterior margin
is more broadly rounded than the anterior margin.
The ultimate podomere of the antenna is about as long as wide, the
penultimate is about four times as long as the ultimate, and the ante-
penultimate is more than one and one-half the length of the penultimate.
The sensory organ of the antepenultimate podomere is extremely long,
reaching past the distal end of the podomere to which it is attached. The
terminal claws are curved near the tip, beyond which the swimming setae
reach a distance equal to three times the length of the terminal claws.
The curved terminal claw of the second thoracic leg (fig. 74) has a
length equal to more than the sum of the distal three podomeres of the
leg. The third thoracic leg (fig. 75) has the “terminal segment... .
three fifths as long as the preceding segment. The longer of the back-
wardly directed setae is longer than the combined lengths of the last three
segments, the shorter one being one fourth as long, or the length of the
last segment; terminal claw half as long as the last segment” (Sharpe,
1897). The furca is somewhat bent, the terminal claw is about one-half
as long as the ventral margin of the ramus, and the subterminal claw is
four-fifths as long as the terminal. Both claws are strongly bent at the
tip. “Terminal seta about as long as width of the ramus; dorsal seta
delicate, two and a half times width of ramus from subterminal claw, and
two thirds as long as ramus is wide” (Sharpe, 1897).
OSTRACODS OF ILLINOIS—HOFF 103
Description of the Male: The male is very adequately described by
Furtos (1935). It is much the same in general shape and size as the
female. The prehensile palps are unequal and elongated; “ejaculatory
duct quite small, with crowns of spines surrounding openings easily
visible, the others quite obscure. Penis roughly quadrangular with a beak-
like terminal lobe” (Furtos, 1935). The male was not observed by the
present writer.
Remarks: Sharpe seems to have made a mistake in regard to the
setae of the penultimate podomere of the third thoracic leg when he
states: “Penultimate podomere three and a half times as long as broad
and armed on the inner edge with but one seta, which is on the middle
of the segment, and half its length’’(Sharpe, 1897). In the individual
observed by the present writer there is a seta in the middle and another
at the distal end of the podomere as is usual in the genus Cyclocypris.
Furtos (1935) pictures two setae of nearly equal length on the penulti-
mate podomere. It is entirely possible that Sharpe examined some
damaged individuals. The present writer has often found, especially in
the Cyclocyprinae, that the distal seta of the penultimate podomere of
the third thoracic leg may easily become broken.
Ecology: The type specimens were collected from a woodland pond
near Bloomington, Illinois, on April 5, 1879 (Sharpe, 1897). Furtos
(1935) took her material from a pond, details of which are not given.
The present writer found a single female in a collection made from mats
of vegetation (Chara, Myriophyllum, and Potamogeton) from a lake
in northeastern Illinois.
Distribution: This species has been reported from McLean County,
Illinois, by Sharpe (1897) and from Falmouth, Cape Cod, Massachusetts,
by Furtos (1935). The writer has it in a single collection from Illinois.
This collection, made by Mr. Bert Wright, was from East Loon Lake,
near Antioch, Lake County, Illinois, on August 7, 1940.
Cyclocypris sharpei Furtos 1933
Cyclocypris laevis Sharpe 1908 (non O. F. Miller 1785). Sharpe, 1908:408-410, pl.
50, fig. 5, pl. 54, figs. 5-7.
Cyclocypris laevis Sharpe 1918 (non O. F. Miller 1785). Sharpe, 1918:822, fig.
1289a, b, c.
Cyclocypris sharpei Furtos 1933. Furtos, 1933:460-461, pl. 14, figs. 8-14.
Type Locality: Ohio.
Description of the Female (after Furtos, 1933): A Cyclocypris species
measuring 0.47 mm. in length, 0.33 mm. in height, and 0.33 mm. in width.
Extremities of shell broadly rounded, posterior somewhat broader ; ventral
104 ILLINOIS BIOLOGICAL MONOGRAPHS
margin slightly convex. The left valve is the larger. Color chestnut-
brown. Ultimate podomere of third leg one-half as long as the penulti-
mate, three times longer than broad. Shortest distal seta one-third as
long as the podomere and often S-shaped. Furcal ramus slightly curved;
dorsal seta usually absent, sometimes rudimentary; terminal claw one-
third as long as the ramus; the terminal seta at least three-fourths the
length of the terminal claw.
Description of the Male (condensed from Furtos, 1933): Similar to
female; length 0.46 mm., height 0.32 mm., breadth 0.32 mm. Prehensile
palps short and unequal; penis roughly globose, with one narrow and
one broad terminal lobe.
Remarks: While it is probable that the true C. laevis of O. F. Miller
does occur in the United States (Turner, 1895), Sharpe (1908) certainly
did not have that species. It seems strange that he did not realize the
differences which occur between his form (now called C. sharpet) and
the true C. laevis of O. F. Muller.
Ecology: Sharpe (1908) reported this species under the designation
C. laevis from ponds and swamps southeast of Chicago, Illinois. Furtos
(1933) reports C. sharpei as being “common in ponds, marshes and
lakes.” There seems to be no seasonal restriction except that collections
so far have not been reported from the haemal season.
Distribution: The species was reported from Illinois (southeast of
Chicago), Indiana, and New York by Sharpe (1908) and from New
Jersey (Sharpe, 1918). Furtos (1933) reports it from several places in
Ohio. The present writer has not found individuals of this species in
any of his collections from Illinois.
Genus CYPRIA ZEenKER 1854
Shell usually short, high (fig. 76), occasionally elongate reniform
(fig. 82) ; strongly compressed; margins smooth, not tuberculate. Eyes
well developed. Second antenna of the male with the penultimate podo-
mere divided and bearing specialized male setae. The ultimate podomere
of the mandibular palp elongated, often as much as three times as long
as the proximal width. Palp of the maxilla well developed, masticatory
processes weak. Penultimate podomere of the third thoracic leg undivided
(fig. 84) ; ultimate podomere short (fig. 89), scarcely longer than wide;
the longest distal seta is reflexed, the two unreflexed setae equal or un-
equal and usually not much longer than the length of the ultimate podo-
mere (figs. 84, 89, 91). Terminal and subterminal claws of the furca
strong, dorsal seta may be rudimentary (figs. 79, 92). Ductus ejacula-
torius with seven whorls of chitinous rays and the proximal end of the
duct much inflated (fig. 93). Penis with two terminal lobes only; outer
OSTRACODS OF ILLINOIS—HOFF 105
lobe wanting (fig. 95). In most species, the females are more numerous
than the males.
The genus Cypris is attributed to Zenker (Zenker, 1854) who used
the name “Cypria” in a subgeneric sense. However, he gave no diagnosis
but described five species in the subgenus. The first available descrip-
tion of the genus Cypria appears to be that given by Brady and Norman
(1889). In order to place C. mediana sp. nov. in the genus Cypria, it
has been necessary to revert to the original diagnosis of Brady and
Norman (1889) rather than the descriptions of later writers who have
restricted the genus in various ways. The principal difficulty in fitting
C. mediana sp. nov. into the genus Cypria as diagnosed by recent authors
is the condition of the setae of the third thoracic leg. According to
Furtos (1933) the third leg is armed distally “with two short and one
long setae, the latter reflexed.” Klie (1938a) restricts the genus Cypria
still more in this respect when he writes “Vorletztes Gl. des Putzfusses
ungeteilt, Endgl. kurz, seine lange Borste zuriickgekriimmt, die beiden
vorwarts gerichteten nicht auffalend verschieden und kaum langer als
das zugehorige Glied.” In C. mediana sp. nov. the shorter of the two
unreflexed distal setae of the third leg (fig. 84) has a length equal to
one and one-half to two times the length of the ultimate podomere and
the longer of the pair is twice the length of the shorter. Brady and
Norman (1889) place no restriction upon the relative lengths of the
distal setae of the third thoracic leg in the genus Cypria.
fety> TO! SPECIES OF THE GENUS CYPRIA IN ILLINOIS
la. Surface of shell marked with closely set parallel and anastomosing longi-
NOCHE NCH MMI NTE Sial (EUS AU ZS) eterno uote ove cisienci rus) ioweck Gone mNbicran Te mestesceaeie vce C. turneri sp. nov.
PaESiniacesot,snell not So: matked...,..s.cus di. cretiretos dian cea odie. les suis baves 2
2a. Shell over 0.70 mm. long; length of the shorter terminal seta of the simi-
larly directed pair on the third leg equal to one-half of the longer of the
Tal URE Ye dy OMe A ees er ea eR Co OR © i Re 3
b. Shell less than 0.70 mm. long; length of the shorter of the pair of similarly
directed setae of the third leg more than one-half the length of the longer
(fig. 91); color bands, blotches, or patches present on shell.................. 4
3a. The length of the terminal claw of the furca almost as long as the ventral
margin of the furca (fig. 85); shell elongate with conspicuous concavity
MPtheRVventralsinarein(Mes80))). 6 as. bcc eee aee oucu ane. C. mediana sp. nov.
b. The length of the terminal claws of the furca little more than three-fifths
of the ventral margin of the ramus; shell suboval with almost straight
BRAIN Trt GAA ETT ACLU e505) cc inela ogo dos; 8's we susiere eoals¥o/e alsa'e a ea C. obesa Sharpe 1897
4a. Three color blotches; one anterior, one posterior, and one behind the eye
(fig. 90) ; length of dorsal seta of furca about equal to the width of the
ramus; subterminal claw of ramus heavily toothed (fig. 92)..C. maculata sp. nov.
b. Small specks of pigment arranged in small patches and scattered over most
of the shell surface (fig. 96) ; dorsal seta of furca has a length about twice
the least width of the ramus; claws of the furcal rami lightly toothed......
SOD MS RAO CET C. ophthalmica (Jurine 1820) Brady and Norman 1889
106 ILLINOIS BIOLOGICAL MONOGRAPHS
Cypria turneri sp. nov.
(Pl. VI, figs. 76-81)
Cypria striolata Herrick 1887 (non Brady 1864, synonym of C. exsculpta (S.
Fischer 1855) ). Herrick, 1887:29, pl. 4, fig. 3.
Cypria exculpta Turner 1894 (non C. exsculpta (S. Fischer 1855)). Turner, 1894:
13-14, pl. 7, figs. 2-8; 1895:305, pl. 70, figs. 1-8; pl. 72, fig. 3.
Cypria exsculpta Sharpe 1897 (non S. Fischer 1855). Sharpe, 1897:465-466, pl. 47,
fig. 4; Kofoid, 1908:258; Shelford, 1913:152; Sharpe, 1918:820, figs. 1283a,
lo} (es Gl
Cypria elegantula Furtos 1933 (non Lilljeborg 1853). Furtos, 1933:465-466, pl. 15,
figs. 8-14; Dobbin, 1941:237, pl. 9, figs. 13-21, pl. 10, figs. 1-2.
Type Locality: Illinois.
Description of the Female: An ostracod of the genus Cypria. From
the side, the shell (fig. 76) is subovate; height equal to a little less than
two-thirds of the length; highest in or very near the middle. The dorsal
margin is strongly arched with a slight flattening anteriorly above the
eye; the anterior and posterior ends are rounded, the anterior end slightly
more narrow than the posterior end. The ventral margin is usually, but
not always, slightly concave. A thin hyaline border is present in both
valves, especially along the anterior and posterior margins. From below
(fig. 77), the shell appears compressed; the greatest width is near the
center and is slightly less than one-half the length of the shell; the an-
terior end is pointed and the posterior end is rounded. The left valve is
slightly the larger. The surface of the shell is marked with peculiar
parallel, frequently anastomosing longitudinal lines (fig. 78) which form
a network over the entire surface of both valves. The color of the valves
is yellow and there are occasionally some light brown markings varying
greatly in intensity and extent. These are usually not as conspicuous,
however, as they are in many species of the genus Cypria, being light in
color and often confined to narrow areas along the anterior and posterior
margins of the valves. There are a few scattered hairs along the margins.
Measurements of valves of several mature females from Illinois are as
follows:
RIGHT LEFT
Length Height Length Height
0.54mm. 0.35 mm. 0.55 mm. 0.35 mm. (holotype)
0.55 0.35 0.56 0.36
0.61 0.38 0.61 0.39
0.56 0.34 0:57 0.35
The length of the sensory organ of the antennae equals in length the
width of the podomere to which the organ is attached, the width of the
podomere being taken at the level of the base of the sensory organ; the
organ reaches to the level of the distal margin of its podomere. Swim-
ming setae of the antennae are variable in length, often reaching beyond
OSTRACODS OF ILLINOIS—HOFF 107
the tips of the terminal claws for a distance about equal to three times
the length of the longest terminal claw. The terminal claw of the second
thoracic leg has a length equal to the sum of the lengths of the ante-
penultimate and penultimate podomeres. These two podomeres are equal
in length. The terminal podomere of the third thoracic leg has a length
equal to about one and one-half times the width; the two distal setae of
the pair are slightly unequal, one having a length nearly equal to the
length of the podomere, the other slightly longer. The terminal seta of
the penultimate podomere of the third thoracic leg is wanting while
the lateral seta arises from the basal one-third of the podomere. The
penultimate podomere is nearly four times the length of the ultimate
podomere. The seta of the antepenultimate podomere reaches scarcely
to the base of the lateral seta of the next distal podomere, being much
shorter than in many Cypria species.
The furca is curved and stout. The ventral margin is seven to seven
and one-half times the least width of the ramus. The size of the furcal
ramus as given by Furtos (1933) for C. elegantula from Ohio is eleven
times the narrowest width. This is evidently an error as the furca which
she pictures (her pl. 15, fig. 11) has a length-width ratio compatible to
that found by the present writer. The dorsal seta of the furcal ramus
has a length equal to nearly two times the least width of the ramus
or to about one-half the length of the subterminal claw. The dorsal seta
is removed from the subterminal claw by a distance equal to two and
one-half times the least width of the ramus or one-third of the dorsal
margin. The terminal seta has a length about one and one-half times the
least width of the furcal ramus. The terminal claw has a length approxi-
mately equal to one-half of the dorsal margin of the ramus and the sub-
terminal claw has a length between four-fifths and five-sixths the length
of the terminal one. Both claws are curved and nearly smooth. The few
distal teeth are so fine that they cannot be seen in well cleared individuals
but may be detected in material mounted in glycerine.
Description of the Male: The shell of the male is similar to that of
the female but slightly smaller. The allotype measures 0.54 mm. in length
and 0.34 mm. in height and is representative of the average size. The
furca (fig. 79) has the same proportions as the furca of the female but
is more curved. The other appendages are essentially like the correspond-
ing ones of the female. The prehensile palps are dissimilar and unequal.
The propodus of the left palp (fig. 80a) is over four times as long as
wide and the sides are rather straight and parallel; the dactylus is very
slender and falciform, being distally recurved. The propodus of the right
palp (fig. 80b) is stouter and shorter than that of the left palp. The
peculiar ventral-distal process of the propodus of the right palp is shown
108 ILLINOIS BIOLOGICAL MONOGRAPHS
in the figure. The dactylus of the right palp is large and highly curved.
It is considerably inflated proximally but tapers to an elongated slender
distal portion. The penis (fig. 81) is peculiar, being not exactly as shown
by Furtos (1933:pl. 15, fig. 14) for C. elegantula of Ohio. In the present
writer’s material, the penis has two lobes each of which has a slender tip.
The inner lobe is proximally widened and flap-like but, unlike the other
indigenous Cyclocyprinae, it is suddenly constricted to a narrow, re-
curved distal point. The middle lobe reaches nearly to the distal end of
the inner lobe. It is slender and gently curved throughout the distal one-
half. Usually only a small percentage of the individuals in any collection
consists of male animals, the females exceeding the males in abundance.
Remarks: Individuals of C. turneri sp. nov. have long been assigned
to the European species C. exsculpta (S. Fischer 1855) Brady and
Norman 1889. Furtos (1933) assigned individuals which apparently are
C. turneri sp. nov. to C. elegantula Lilljeborg 1853 although the latter
is a synonym of C. exsculpta (S. Fischer 1855). Although “elegantula”
is an older specific name than “exsculpta,” it is invalid because the name
“elegantula” was used by S. Fischer in 1851 for individuals now known
to belong to the species C. ophthalmica (Jurine 1820). Although C.
elegantula (Fischer 1851) has become a synonym of C. ophthalmica
(Jurine 1820), C. elegantula cannot be used in place of C. exsculpta
(S. Fischer 1855). C. exsculpia (S. Fischer 1855) 1s thea@thewyaun
designation of the European species into which many writers have placed
individuals belonging to a closely related American species which is
described herein as C. turneri sp. nov.
The correctness of assigning this American Cypria species, which is
characterized by parallel longitudinal lines on the shell, to the European
species C. exsculpta has been questioned by several writers. G. W.
Miller (1912) questioned Turner’s identification of the American form
and did not even mention the form listed by Sharpe under the European
name. Furtos (1933) states “There is a possibility that the Ohio species
should not be referred to elegantula of Europe.”’ She supported her con-
tention by noting the difference in size of the shell, the difference in the
penis, and the “smooth furcal claws” of the European species. Regard-
ing the last item, Furtos was incorrect as the claws of the individuals of
C. exsculpta of central Europe are toothed according to Kaufmann
(1900a) who says that the furca “tragt am Ende zwei schmale, gezah-
nelte Klauen.”
After a study of many complete descriptions of the Cypria exsculpta
indigenous to Europe and after examining a large series of C. turneri
from Illinois, the writer has found the following substantial differences
OSTRACODS OF ILLINOIS—HOFF 109
between the true C. exsculpta of S. Fischer and the American species
now designated as C. turneri sp. nov.
C. exsculpta (S. Fischer) C. turneri sp. nov.
Shelllength, female..........20'...¢0% Over 0.70 mm. Under 0.65 mm.
Shell height/length ratio.............. Over 70% Under 65%
Wentral margin of shell... .....5....6:. Convex Straight or concave
See CRE NOLACIG IER. aso a. cieie ae se aie oe ene Seta of penultimate Same near basal one-
podomere near third of podomere;
center; ultimate ultimate podomere
podomere elongated relatively short
BIDE. o's SBS A OE Oi ee ee eee Oval; inner lobe not Elongate; inner lobe
distally recurved hook-like distally
hook-like
PLE REN SUES PAIDGic- | efevc.c 5 bce ote valet Propodus of right and Propodus of left palp
left palps equal longer than that of
right
DNGtHSTeyaCUlAtONUS. 6s... .0.660,000+ Oval Elliptical; elongate
Because there are fixed differences and there appears to be no tran-
sition between the European C. exsculpta and the American C. turneri,
they are certainly separate and distinct morphological species. The use
of the characteristic longitudinal lines as the main taxonomic criterion
for the recognition of the species C. exsculpta without checking any of
the other structures probably led to the early, easily perpetuated error in
designation. The specific name, “turneri,” suggested for this new species
is in memory of C. H. Turner, one of the outstanding early workers on
American Entomostraca.
Ecology: C. turneri sp. nov. is found only in ponds and lakes, never
in running waters except in backwaters of rivers or quiet pools of
small, usually vernal streams. It is very abundant in temporary ponds.
Under the name C. exsculpta, Shelford (1913) reports this species as
common in ponds of the Chicago region. Sharpe (1897) writes that this
species is common in most “running streams’”’ but the present writer with
few exceptions has not found this species in streams. It is often found
associated with algae, water plants, and grass but may be found in open
water as an occasional constituent of plankton. This species is very
abundant from March to late June but is sometimes found in the sero-
tinal and autumnal seasons.
Distribution: This species has been reported under the name C.
exculpta or C. exsculpta from Alabama (Herrick, 1887), from Ohio,
Georgia, and Delaware by Turner (1894), from Maine by Procter
(1933), and from Illinois by Sharpe (1897), Kofoid (1908), and Shel-
ford (1913). The Cypria exsculpta mentioned by Creaser (1931) as oc-
curring in crayfish burrows in Missouri is probably also this species.
Under C. elegantula, this species has been reported from Ohio by Furtos
110 ILLINOIS BIOLOGICAL MONOGRAPHS
(1933) and from Washington and Alaska by Dobbin (1941). Since it
has been long confused with the European species C. exsculpta (S.
Fischer 1855), it is impossible to determine its range. C. turneri sp. nov.
is probably confined, however, to the Nearctic region. The present writer
has taken it in collections from counties in many parts of the state of
Illinois.
The holotype (female), allotype (male), and a paratype (female)
are deposited in the U. S. National Museum (Cat. Nos. 81078, 81079, and
81080). Paratypes (male and female) are in the collections of Dr. H. J.
Van Cleave, Dr. Arthur G. Humes, and the writer.
Cypria mediana sp. nov.
(Pl. VI, figs. 82-87)
Type Locality: Ilinois.
Description of the Female: A species of the genus Cypria. Shell
(fig. 82) elongate; height equal to little more than one-half the length,
greatest near the center or somewhat anterior to the center. The left
valve is slightly larger than the right. The dorsal margin forms a low
arch, blending without interruption into the anterior and posterior
margins except for a very weak sinuation which, especially in the right
valve, may occur near the anterior end. The anterior and posterior ends
are evenly rounded; the posterior is more narrow than the anterior. The
ventral margin is concave, the concavity being deepest in the center of
the posterior two-thirds of the shell. Pore-canals are present only along
the ventral margin of the left valve. A hyaline border is found along
the ventral, posterior, and anterior margins of each of the valves. The
muscle scars are nearly centrally placed; six scars, five of which are
large and one of which is inconspicuous, are found arranged in a loose
group; a small isolated scar is located dorsal-anteriorly of the group
while a pair of long scars are found anterior and slightly ventral of the
group. A few hairs are evident along the anterior margin of the shell.
Flakes of pigment may occur on the anterior and posterior slopes of the
valves. The valves of three mature females from Illinois (mounted in
diaphane) measure as follows:
RIGHT LEFT
Length Height Length Height
0.94 mm. 0.50 mm. 0— mm. 0.52 mm. (holotype)
0.90 0.54 0.91 0.58
0.88 0.48 0.90 0.49
Shell from below (fig. 83): compressed, pointed posteriorly and an-
teriorly; greatest width in the anterior one-half of the shell and approxi-
mately equal to two-fifths of the length.
OSTRACODS OF ILLINOIS—HOFF 111
Each antenna consists of five podomeres; the sensory organ has a
length slightly less than the distal width of the third podomere. The
swimming setae of the antennae extend beyond the tips of the terminal
claws for a distance little longer than the length of the claws. The
terminal claws and the claws of the penultimate podomere are very long
and slender; the claws of the penultimate podomere reach distally beyond
those of the ultimate podomere. The ultimate podomere of the man-
dibular palp is nearly twice as long as the width at the base; the distal
claws are of greatly varying lengths, the longest at least twice the length
of the ultimate podomere. The processes of each maxilla are short; the
palp is of two podomeres and has the short terminal podomere distally
widened, with three nearly equal spine-like setae and several smaller ones.
The second thoracic leg with the antepenultimate and penultimate
podomeres equal; the ultimate podomere small, about as long as the
basal width. The distal claw of the second leg is approximately equal
to one and one-half times the combined lengths of the distal three
podomeres. Of the two terminal setae approximate to the distal claw,
one is approximately as long as the penultimate podomere, the other two-
thirds as long. The third thoracic leg (fig. 84) has the antepenultimate
and penultimate podomeres nearly equal in length. The ultimate podo-
mere is but little longer than wide. Of the two unreflexed distal setae,
the shorter is one and one-half to two times the length of the ultimate
podomere, and the longer is twice the shorter. The distal seta of the
penultimate podomere is reduced to a short spine and is surrounded
by a crown of fine bristles; the lateral seta of the penultimate podomere
is attached near the anterior end of the basal half of the podomere and
reaches beyond the distal end of the podomere. The distal seta of the
antepenultimate podomere measures between one-half and two-thirds the
length of the podomere and reaches at least to the base of the lateral seta
of the penultimate podomere. Lateral hairs are present along the sides
of the antepenultimate and penultimate podomeres.
The ventral margin of the furca (fig. 85) is slightly curved and
measures less than seven times the least width. Dorsal seta but little
longer than the least width of the ramus and removed from the sub-
terminal claw by a distance equal to a little more than twice the least
width of the ramus, or about one-third of the length of the ventral
margin of the ramus. The terminal claw is almost as long as the ventral
margin of the ramus; the subterminal claw is four-fifths as long as the
terminal. The terminal seta is equal in length to one-third of the terminal
claw. Both claws are so finely toothed that superficially they appear
smooth.
Description of the Male: Shell in general appearance like the female
but smaller. The right valve (fig. 86) of the allotype (mounted in dia-
12 ILLINOIS BIOLOGICAL MONOGRAPHS
phane) measures 0.82 mm. in length and 0.44 mm. in height; the left
valve measures slightly more. The testes are much larger than in most
species of the genus Cypria. In the right valve, there is a slight sinuation
at both ends of the dorsal margin. The appendages are similar to those
of the female except the claw of the second leg is relatively longer. The
prehensile claws and ductus ejaculatorius are Cypria-like and offer no
special details. The penis (fig. 87) has a rather wide, flap-like, and blunt
inner lobe and a narrow, chitinized middle lobe with a curved tip.
Remarks: C. mediana sp. nov. with the exception of two or three
details of structure fits into the genus Cypria as usually diagnosed. The
shell is more elongate than is usual in individuals of the genus and the two
distal setae belonging to the pair on the ultimate podomere of the third
leg are more unequal in length, resembling a Candona species in this
respect. However, the nature of the setae of the penultimate podomere
of the third leg is typically that of a Cypria species. The male sexual
‘organs are those of the subfamily Cyclocyprinae. The placing of this
species in the genus Cypria has made necessary certain relatively unim-
portant emendations to the genus. These have been discussed under the
diagnosis of the genus.
Ecology: Of the three collections made by the writer containing
C. mediana sp. nov., one came from a grass covered area in an ox-bow,
one from water plants in a pool of a dried up stream, and the third from
water plants and old leaves along the edge of a sluggish vernal stream.
Individuals of this species seem to tolerate an acid environment. All of
the individuals taken were mature and were taken in the first ten days
of June, 1940.
Distribution: This species is known only from southern Illinois, having
been taken by the writer in a single collection from Johnson County, one
from Marion County, and a third from Massac County, Illinois. The
writer has not found this species in the northern one-half of the state.
The holotype (female) and allotype (male) of this species are de-
posited in the U.S. National Museum (Cat. Nos. 81081 and 81082). One
paratype (female) is in the collection of Dr. H. J. Van Cleave and para-
types of both sexes are retained in the writer’s collection.
Cypria obesa Sharpe 1897
(Pl. VII, figs. 88-89)
Cypria obesa Sharpe 1897. Sharpe, 1897:462-463, pl. 48, figs. 1-5; 1918:821, figs.
1285a, b, c, d; Furtos, 1933:466-467, pl. 15, figs. 1-7.
Type Locality: Havana, Mason County, Ilinois.
Description of the Female: A Cypria species. Shell (fig. 88) brown-
ish in color, plump; suboval with nearly straight ventral margin. Height
OSTRACODS OF ILLINOIS—HOFF 113
about three-fifths of the length. Length varies from 0.74 to 0.86 mm.,
height from 0.44 mm. to 0.52 mm. The sensory organ on the inner edge
of the third podomere of the antenna short; natatory setae extend beyond
the tips of the terminal claws by twice the length of the claws. Last
podomere of the third thoracic leg (fig. 89) slightly longer than wide;
shortest distal seta equal to the length of the ultimate podomere; the
longer of the pair twice the shorter. The distal seta of the penultimate
podomere of the third leg much reduced and surrounded by a crown
of fine bristles. Furca with terminal claw three-fifths as long as the
ramus. Terminal seta about one and one-half times the least width of
the ramus and the dorsal seta about as long as the width of the ramus.
The dorsal seta is located a distance of three times the least width of the
ramus from the subterminal claw.
Description of the Male: Slightly smaller than the female, otherwise
similar. Prehensile palps dissimilar and unequal. Penis triangular with
two subequal terminal lobes.
Remarks: The writer’s specimens are identical with those described
by Sharpe with the exception that the furcal ramus has a smooth dorsal
margin instead of the toothed margin as described by Sharpe (1897).
Furtos (1933) also noticed this incompatibility between her specimens
and the description of Sharpe.
Ecology: Sharpe (1897) took this species fromthe sandy shore of
a lake in central Illinois and Furtos (1933) reports it from a stone-
quarry pool and a cold spring in Ohio. The present writer has found
it as a rule associated with submerged grasses and water plants in shallow
water, more often than not over a mud bottom. In fact, in seven out of
eight places where this species was collected, there was an abundance
of vegetation, as is common along the edges of river backwaters, swamps,
and temporary vernal pools. In one instance, this species was taken from
a muddy pool where there was no vegetation but as this pool was a
remnant of a much larger one, it is entirely possible that this form was
merely a survivant. All of the collections containing this species were
made in quiet waters except that one collection was made from weeds
and old leaves in a small stream not over five feet wide and having a very
slow current and another was from the edge of Rock River where there
was little current. This species seems to be characteristic of the aestival
season rather than the vernal as is common with many Cypria species.
Distribution: This species has been previously reported from Havana,
Mason County, Illinois, by Sharpe (1897) ; from Jackson Park, Chicago,
Illinois, by Sharpe (1910); and from Newark and Granville, Ohio, by
Furtos (1933). The present writer has collected C. obesa from six
counties in Illinois. With the exception of Massac County which is at
114 ILLINOIS BIOLOGICAL MONOGRAPHS
the southern tip of the state, all of the Illinois reports for this species
are from the northern one-half of the state.
Cypria maculata sp. nov.
(Pl. VII, figs. 90-95)
Cypria opthalmica (at least in part) Turner 1895 (non C. ophthalmica (Jurine
1820)). Turner, 1895:306, pl. 75, figs. 1-3, 7; pl. 76, figs. 1-3, 5.
Cypria ophthalmica Sharpe 1897 (non Jurine 1820). Sharpe, 1897:466-468, pl. 47,
fig. 5; Kofoid, 1908:258.
Cypria ophthalmica (at least in part) Sharpe 1918 (non Jurine 1820). Sharpe,
1918:821, figs. 1284a, b, c, d.
Type Locahty: Illinois.
Description of the Female: A species belonging to the genus Cypria.
Shell (fig. 90) from the side reniform; the dorsal margin forming a
high arch slightly flattened anteriorly where it passes into the anterior
margin near the eye. The anterior and posterior margins rounded, the
posterior more broadly so. The ventral margin is nearly straight. The
pore-canals are very short as a result of the proximity of the submargin
and margin; the hyaline border of the valves common to many species
of Cypria is absent. The muscle scars are nearly centrally located. From
above, the shell appears compressed, greatest width less than the greatest
height but more than one-half of the length of the shell; “widest at the
posterior third, narrow, somewhat acutely pointed anteriorly and rounded
posteriorly” (Sharpe, 1897). There are a few hairs scattered over the
surface of the valves and each valve is marked with three irregular
brown to reddish-brown blotches. One of these is on the anterior slope
of each valve, another along the dorsal margin behind the eye, and the
third is on the posterior slope of each valve. The length and height of
several valves of mature females are as follows:
RIGHT LEFT
Length Height Length Height
0.54 mm. 0.37 mm. 0.54mm. 0.38 mm. (holotype)
0.54 0.38 0.54 0.39
0.55 0.38 0.56 0.39
0.50 0.34 0.50 0.35
0.48 0.33 0.48 0.34
The swimming setae of the antennae extend beyond the tips of the
distal claws for a distance equal to three times the length of the distal
claws. The sensory organ of the antenna has a length less than one-half
of the length of the podomere which bears it. The terminal podomere
of the mandibular palp is very long, being three times as long as the
greatest width; distally it is only about one-half as wide as proximally.
OSTRACODS OF ILLINOIS—HOFF 115
The ultimate podomere bears, among others, two long setae which are
at least one and one-half times as long as the ultimate podomere. On the
outer margin of the penultimate podomere of the mandibular palp near
the distal end is a group of four long setae which reach considerably
beyond the distal margin of the ultimate podomere. The second thoracic
leg with the proximal width of the ultimate podomere equal to or greater
than the length of the podomere; terminal claw slightly less or equal
in length to the sum of the lengths of the distal three podomeres. Ante-
penultimate podomere with a length equal to that of the penultimate
podomere.
The penultimate podomere of the third thoracic leg (fig. 91) has a
length little more than three times the greatest width and is longer than
the antepenultimate podomere; the seta of the penultimate podomere
arises proximal to the center of the podomere and reaches nearly to the
level of the distal end of the podomere. The seta of the antepenultimate
podomere reaches over a third of its length beyond the base of the seta
of the penultimate podomere. A crown of bristles is present at the distal
outer margin of the penultimate podomere but does not surround a distal
seta as happens in many Cypria species. One of the seta of the crown
is enlarged and spine-like. The ultimate podomere is a little longer than
wide; the ventral margin is sinuated. Sharpe (1897) writes that the
inner margin of the ultimate podomere of the third leg is sinuated; evi-
dently he made an error in orientation of the appendage. The terminal
setae of the similarly directed pair are nearly equal and but little longer
than the length of the ultimate podomere which bears them. The furca
(fig. 92) is somewhat curved; the length of the ventral margin is between
seven and eight times the least width of the ramus. The margin of the
ramus is smooth. The dorsal seta has a length less than the least width
of the ramus and is removed from the subterminal claw by a distance
equal to three times the least width of the ramus, being, therefore, nearer
the midpoint of the dorsal margin than the distal one-third. The terminal
seta is longer than the dorsal seta, having a length nearly twice the least
width of the ramus. The terminal claw is gently curved and smooth.
It has a length equal to five-eighths of the ventral margin of the ramus
or about one-half of the dorsal margin. The subterminal claw measures a
little more than three-fifths of the terminal claw and is very heavily
toothed.
Description of the Male: Shell of the male the same size and shape
as that of the female. The appendages are similar. Ductus ejaculatorius
(fig. 93) elongate and with the general characteristics of the subfamily.
Prehensile palps dissimilar and unequal. The right palp (fig. 94b) is
stout, distally enlarged, with the propodus terminating in a distal process
116 ILLINOIS BIOLOGICAL MONOGRAPHS
extending beyond the dorsal margin of the heavy, hook-like dactylus.
The left palp (fig. 94a) is more slender than the right, the propodus is
not distally enlarged and the dactylus is narrow and distally reflexed. The
penis is wide (fig. 95), with the middle lobe tapering, flap-like; the inner
lobe much more slender, somewhat curved distally, having the outer
margin chitinized, and shorter than the lappet-like middle lobe.
Remarks: It is unfortunate that Turner (1895) and Sharpe (1897)
confused this species with the true C. ophthalmica described by Jurine in
1820. While certain similarities do exist, there are many conspicuous
differences. G. W. Miller (1912) questioned the identification of C.
ophthalmica as made by Turner in 1895. At the same time, Miller
omitted entirely Sharpe’s reference of 1897 to C. ophthalmica from Ml-
nois. Whether this omission was intentional because he doubted Sharpe’s
identification or whether it was an oversight on Miller’s part cannot
now be ascertained. Though C. ophthalmica and C. maculata are closely
related species, they may be separated definitely upon the following
characters:
C. ophthalmica
(Jurine 1820)
Shell length, female................ Seldom under 0.55 mm.
Golonioftshellll cute eee sen ee Most of shell covered
with isolated colored
patches
Antenna, sensory organ............. 34 length of its
podomere; almost
reaches distal
Third leg, distal seta of penultimate end of podomere
podomere.h.sccic eee eer ne Reduced to a spine
surrounded by a
C. maculata sp. nov.
Seldom over 0.55 mm.
Three definite colored
patches or areas
¥ length of podomere
and does not almost
reach distal end of
podomere
Small, a part of the
crown of bristles
crown of bristles
Furca, length of dorsal seta......... Almost twice the least
width of the ramus
About the same as the
least width of the
ramus
PuLca, dorsal matoim. * = .a5%.seas <6 1 Toothed Smooth
Furca, subterminal claw............ Weakly toothed Heavily toothed
Right prehensile claw of male........ Propodus not much Propodus much en-
enlarged distally larged distally
There is a remote possibility that Cypria maculata sp. nov. should be
referred to Physocypria dentifera (Sharpe 1897) G. W. Miller 1912. The
absence, however, of the definite “tuberculiform teeth” (Sharpe, 1897)
on the anterior margin of the left valve, the absence of the hyaline border
along the anterior of the right shell margin, and the greater size of the
shell would certainly be sufficient reason for recognizing Physocypria den-
tifera and Cypria maculata as apparently separate species. Occasionally
a right valve of C. maculata may be found bearing on the anterior
margin rudimentary tubercles but the writer has never found such
tubercles on the margin of the left valve. As the writer has no individuals
OSTRACODS OF ILLINOIS—HOFF 117
of Physocypria dentifera for comparison with Cypria maculata, it is
impossible to determine the exact relationship between the two species.
Whether or not Physocypria dentifera represents a variable series which
includes Cypria maculata will depend upon a detailed study made from
an abundance of material of both species. Until such a study is made,
Sharpe’s Physocypria dentifera and the writer’s Cypria maculata must
stand as valid species.
Ecology: Unlike the closely related species C. ophthalmica, C. macu-
lata sp. nov. is usually found in clean, alkaline waters. It may be found
in vernal ponds, the shores of lakes, and along the edges of streams where
the current is slowed up by the presence of aquatic plants. It seems to
prefer habitats where there are algal masses, grasses, and water plants
and is only in rare instances found associated with decaying vegetation.
Distribution: Through the uncertainty of the exact designation of
C. ophthalmica as used by Sharpe (1918), it is impossible to give the
corrected distribution for this species. Sharpe (1918) gives the distri-
bution as Georgia, Illinois, Minnesota, and Oregon for C. ophthalmica,
but since Sharpe’s conception of C. ophthalmica was probably a mixture
of the true C. ophthalmica of Jurine and what is herein designated as
C. maculata sp. nov., the distribution records are almost valueless. The
present writer has taken this species from counties in nearly all parts of
Illinois.
The holotype (female) and allotype (male) of this species are de-
posited in the U. S. National Museum (Cat. Nos. 81083 and 81084).
Paratypes (male and female) are in the collections of Dr. H. J. Van
Cleave, Dr. Arthur G. Humes, and the writer.
Cypria ophthalmica (Jurine 1820) Brady and Norman 1889
(Pl. VII, figs. 96-97)
Monoculus ophthalmicus Jurine 1820. Jurine, 1820:178, pl. 19, figs. 16, 17.
Cypria ophthalmica (Jurine 1820) Brady and Norman 1889. Brady and Norman,’
1889:69, pl. 11, figs. 5-9.
non Cypria opthalmica (sic!) (in part?) Turner 1895. Turner, 1895:306, pl. 75,
figs. 1-3, 7; pl. 76, figs. 1-3, 5.
non Cypria ophthalmica Sharpe 1897. Sharpe, 1897:466-468, pl. 47, fig. 5.
non Cypria opthalmica (sic!) Sharpe 1918. Sharpe, 1918:821, fig. 1284.
Cypria ophthalmica (Jurine 1820) Brady and Norman 1889. Kaufmann, 1900a:336-
341, pl. 20, figs. 1-3; pl. 23, figs. 15, 16; pl. 29, fig. 20.
Cypria opthalmica (sic!) (Jurine 1820) Brady and Norman 1889. Sars, 1928:97-98,
pl. 45, fig. 1.
Type Locality: Central Europe.
Description of the Female: An ostracod of the genus Cypria. Shell
(fig. 96) short and high; seen from the side, the dorsal margin is strongly
118 ILLINOIS BIOLOGICAL MONOGRAPHS
arched, both anterior and posterior ends broadly rounded, the posterior
more so than the anterior. The ventral margin is either straight or
weakly sinuated in the center. There is a hyaline border along the
anterior and posterior margins of the shell. The left valve is very slightly
larger than the right. Measurements of several mature females from
Illinois are as follows:
Length Height
0.61 mm. 0.41 mm.
0.60 0.42
0.63 0.44
0.56 0.36
0.60 0.40
Surface of the valves without sculpturing but covered with pigment
spots (fig. 97), each spot being made up of little flecks of pigment;
these spots are usually more conspicuous along the anterior, posterior,
and dorsal margins of the shell than they are in the central part of
each valve.
The swimming setae of the antennae extend beyond the tips of the
terminal claws a distance equal to more than three times the length of
the terminal claws. The distal end of the sensory organ on the side of
the antepenultimate podomere is almost at a level with the distal end
of the podomere. The distal podomere of the mandibular palp is very
much elongated, being three times as long as the greatest width of the
podomere. The masticatory processes of the maxilla are short. The
palp of the maxilla has a wide, proximal podomere and a distal podomere
which is small and is attached to the ventral distal angle of the first
podomere. On the distal margin, the ultimate podomere bears some
bristle-like setae fully twice as long as the length of the podomere. The
claw of the second thoracic leg is equal or slightly subequal to the sum
of the lengths of the last three podomeres. The last podomere of the
third thoracic leg is nearly as wide as long; the two shorter setae are
slightly unequal, one being a little less, the other a little more than the
length of the podomere to which they are attached. The penultimate
podomere bears a distal seta reduced to a spine and a long seta near the
basal one-third of the podomere. This latter seta reaches to the distal
margin of the podomere. The margins of the penultimate and antepenulti-
mate podomeres bear many fine hairs. The furcal ramus is stout and
slightly curved. The ventral margin of the furca is approximately seven
times the least width. The dorsal margin of the furcal ramus is finely
toothed throughout most of its length. The apical claws are well developed,
the terminal one being two-thirds the length of the ventral margin of the
OSTRACODS OF ILLINOIS—HOFF 119
ramus. The terminal seta is approximate in length to the least width of the
ramus; the dorsal seta approaches twice the width of the ramus.
Description of the Male: The male is slightly smaller than the female.
The coloration and general appearance is the same. In the male, the
swimming setae of the antennae are shorter, extending beyond the tips
of the terminal claws for a distance little more than twice the length of
the claws. The prehensile palps are much unequal and dissimilar; the
right one being much more highly developed as a prehensile structure
than the left. The terminal lobes of the penis are well produced, the
inner one being somewhat shorter and more acute at the distal end than
the middle one. The males are not very numerous in any collection. This
also has been noticed by Klie (1938a): “Die 22 sind stets Zahlreicher
als die $6.”
Remarks: It is very unfortunate that Sharpe (1897) mistook indi-
viduals of another species (C. maculata mihi) for this easily identified
European species. A comparison of the species Sharpe called C. ophthal-
mica with the true C. ophthalmica of Jurine is made under the remarks
in the description of C. maculata sp. nov.
Individuals assigned herein to C. ophthalmica agree in all important
details with European descriptions of this species. The only noticeable
differences are a slightly greater inequality in the two shorter distal
setae of the third thoracic leg and a somewhat greater length of the
dorsal and terminal setae of the furca in the American form. These
differences are so slight, however, that they may be assigned to species
variation. That great variation in size, shape, as well as general propor-
tions of various structures occur in this species is well known as Kauf-
mann (1900a) writes: “Die Dimensionen scheinen auch bei dieser Form
in den einzelnen Landern erheblich zu differieren.”
It is very improbable that Cypria neglecta Herrick 1879 is a synonym
of C. ophthalmica Jurine, although both Turner (1895) and G. W. Miller
(1912) consider it possible but questionable. From the size of the shell
as given by Herrick (1879), “little exceeding 0.01 in.,” one might reason-
ably suppose that Herrick examined immature individuals. His drawings
(Herrick, 1879:pl. 17, figs. 2c, 2d) of the furca and the antennae (“‘in-
ferior antennae’) point to either immature individuals or abnormal ones
although his drawing of the ductus ejaculatorius seems to be from a
mature male. From the description given by Herrick, “color dull white,
without markings of any kind,” it is necessary to conclude that he did not
have either the C. ophthalmica of Jurine or of Sharpe (C. maculata) as
the color markings are without exception prominent in these two species.
From Herrick’s inadequate description and apparently erroneous figures,
120 ILLINOIS BIOLOGICAL MONOGRAPHS
it is not safe to reassign his Cypria neglecta to any known species of
Cypria.
Ecology: There is a wealth of ecological data regarding this species
in European waters (Kaufmann, 1900a; Alm, 1916; Klie, 1938a). In
general, the species has been reported as living in “Kleineren, austrock-
nenden Gewassern aller Art, als auch in Grosseren Teichen und beson-
ders am Grunde der Seen gefunden” (Alm, 1916). The present writer
has collected C. ophthalmica only from waters which contain an abun-
dance of decaying material and where, in some instances, the pH indicates
a highly acid condition. In one collection made by the present writer from
a ditch in Franklin County, Illinois, the water had a pH of 6.4. In
another instance, individuals belonging to this species were collected
by Robert Yapp from a cypress swamp at Reelfoot Lake, Tennessee,
where the pH was 6.8. No individuals of this species have been taken
from the distinctly alkaline waters of the northern part of the state of
Illinois. It is evident that this species tolerates an acid condition of the
water and perhaps prefers it to an alkaline condition. That this species
tolerates distinctly “spoiled” waters was also noticed by Kaufmann
(1900a) who writes: “Sie... . ist sehr widerstandsfahrig gegen das
Verderben des Wassers, sowie gegen Temperaturunterschiede.” There
appears to be no seasonal restriction upon the distribution of this species.
Distribution: In general, this species is distributed over most of the
Holarctic region and South America as well (Daday, 1905). Because
of the uncertainty of Turner’s identification (Turner, 1895), it is im-
possible to state definitely the distribution previously reported for North
America. However, Turner’s report of its occurrence in Georgia is
probably correct. The report by Dobbin (1941) of this species in the
Pacific region constitutes without doubt a valid record since her de-
scription checks closely with the present writer’s. This species has been
collected in several counties of central and southern Illinois. The writer
has also found C. ophthalmica in collections made by Mr. Robert Yapp
in the vicinity of Reelfoot Lake, Tennessee.
Genus PHYSOCYPRIA VAvra 1897
The margin of either the right or the left valve has a row of tu-
bercles or pustules which may be confined to the anterior margin alone
or may be found on portions of the anterior, posterior, and ventral
margins. Otherwise as in the genus Cypria.
Two species of this genus, P. pustulosa (Sharpe 1897) G. W. Miiller
1912 and P. dentifera (Sharpe 1897) G. W. Miller 1912, are known
from Illinois.
OSTRACODS OF ILLINOIS—H OFF 121
ee TO; SPECIES OF THE GENUS PHYSOCYPRIA IN ILLINOIS
a. Many tubercles along the anterior margin and a few to many along the
posterior margin of the right valve (fig. 98); terminal claw of the furca
equal approximately to one-half of the length of the ramus..............
coc ct ced 3 EE POR RS eeeR eeeea P. pustulosa (Sharpe 1897) G. W. Muller 1912
b. Many fine tubercles along the anterior margin only of the left valve; ter-
minal claw of the furca approximately equal to three-fifths of the length of
REREMITIT CAMS Peters ce owe ccalsie as P. dentifera (Sharpe 1897) G. W. Miller 1912
Physocypria pustulosa (Sharpe 1897) G. W. Miller 1912
(Pl. VII, fig. 98)
Cypria pustulosa Sharpe 1897. Sharpe, 1897:461-462, pl. 48, figs. 6-10; Kofoid,
1908: 258.
Cypria (Physocypria) pustulosa Sharpe 1897. Sharpe, 1918:821, figs. 1284a, b, c, d, e.
Physocypria pustulosa (Sharpe 1897) G. W. Miller 1912. G. W. Miller, 1912:134;
Furtos, 1933:470, pl. 16, figs. 10-11.
Physocypria globula Furtos 1933. Furtos, 1933:468-469, pl. 16, figs. 1-9.
Type Locahty: Mason County, Illinois.
Description of the Female: An ostracod of the genus Physocypria.
The subovoid shell (fig. 98) shows considerable variation in both size
and shape. The dorsal margin forms a high arch. Both the anterior
and posterior margins are rounded, the posterior more broadly. The
ventral margin is usually nearly straight but may have a slight centrally
located sinuation. The left valve is slightly larger than the right. The
greatest height of the shell is about two-thirds of the length and is at
the center of the dorsal margin or slightly anterior or posterior to the
center. Seen from above the shell is compressed with the greatest width
considerably less than the greatest height. Several shells of mature
females from Illinois measure as follows:
Length Height
0.52 mm. 0.40 mm.
0.56 0.42
0.59 0.43
0.49 0.31
0.48 0.36
0.62 0.46
0.48 0.30
The shell is moderately hairy; the eyespot is very large; the shell is
marked with brown or reddish-brown blotches or patches. One of these
is located anteriorly, another above and posterior to the eyespot, and the
third is on the posterior part of the shell.
The most important single criterion of this species is the presence
of tubercles upon the margin of the right valve. These tubercles are
122 ILLINOIS BIOLOGICAL MONOGRAPHS
highly variable in position, number, and size. The tubercles on the
anterior margin of the shell are rather small and range from as few
as ten to as many as twenty-five in number. A few of them may pass
around the margin of the valve to the anterior end of the ventral margin.
The tubercles are usually largest in the center of the row and become
weaker toward the two ends, the weakest of the tubercles being barely
distinguishable. The tubercles of the posterior and posterior-ventral
margin present still greater variability. Occasionally they are almost
unrecognizable, only rudiments appearing to mark the position of the
larger tubercles. In the form described by Sharpe as C. pustulosa
(Sharpe, 1897) there are three or four tubercles just posterior to the
ventral sinuation. These are commonly not conical but are flattened and
pointed posteriorly. On the right valve of other individuals (designated
as C. globula by Furtos (1933)) these few large tubercles are followed
posteriorly by a row of small, distinct tubercles along the posterior
margin. The number and size of these tubercles vary; there may be only
one or two or there may be nearly as many as there are tubercles on the
anterior margin of the valve. With respect to the tubercles there appears
to be no dividing line between the pustulosa form of Sharpe and the
globula form of Furtos. This is considered further under the heading
“remarks.”
The swimming setae of the antennae are long, reaching a distance
equal at least to three times the length of the terminal claws beyond the
tips of the claws. The sensory organ of the third podomere is rather
short, reaching only to the distal one-fourth of the podomere. The
terminal podomere of the maxillary palp is nearly square in outline and
bears distally three well developed but unequal setae and several smaller
ones. The terminal podomere of the third thoracic leg is but little longer
than wide. The two short distal setae are subequal, the longer one being
slightly longer than the ultimate podomere of the leg. The penulti-
mate podomere of the third leg has a long seta with the base just below
the middle of the podomere and the tip reaching to the distal margin
of the podomere. The podomere bears at the distal end a very small,
vestigial seta and a crown of fine bristles. The inner margin of the
antepenultimate and ultimate podomeres of the third leg bear numerous
long hairs. The furca is long and narrow, the ventral margin usually
eight to nine times as long as the least width of the slightly curved ramus.
The dorsal seta varies from about one to one and one-half times the least
width of the ramus and is located a little distal of the center of the
dorsal margin of the ramus. The terminal seta is usually a little longer
than the dorsal one. The terminal claw has a length equal to approxi-
mately one-half the length of the dorsal margin of the ramus. The sub-
OSTRACODS OF ILLINOIS—HOFF 123
terminal claw is about two-thirds the length of the terminal one. The
terminal and subterminal claws are gently curved; the terminal is smooth,
the subterminal has a row of fine teeth near the tip.
Description of the Male: The male is somewhat smaller than the
female; otherwise similar. The prehensile palps are Cypria-like and are
of little distinctive taxonomic importance. The penis has the outer lobe
wanting; the inner lobe is relatively long, pointed, and curved; and the
middle lobe is rather flap-like, not very wide, blunt at the distal end, and
reaches about the same level distally as the inner lobe.
Remarks: Physocypria pustulosa is an extremely variable species of
ostracod. The variation is evident in the shell shape; length to height
ratio of the shell; the number, position, and size of the tubercles on the
shell; the lengths of the setae on the third thoracic leg; and the lengths
of the dorsal and terminal setae of the furca. In working with several
hundred individuals selected from one hundred and thirty collections,
the writer has found it impossible to divide the variable series represent-
ing this species into either morphological species or subspecies. It is
possible, as Furtos (1933) may have done, to select individuals from the
ends of the series and set them aside as different species based entirely
upon the number and arrangement of the tubercles of the shell margin.
However, when a large series is at hand, it is evident that P. globula
Furtos 1933 and P. pustulosa (Sharpe 1897) are really a single species.
In most population samples, it is possible to find individuals which have
the typical pustulosa type of posterior-ventral tubercles and have in ad-
dition a few extremely small, rudimentary tubercles which might easily
be overlooked. Very often, the number of pustules or tubercles on the
anterior margin of the shell is distinctly too many for Sharpe’s species,
and corresponds accurately with the number given by Furtos for the
globula type. Posteriorly, however, the same shell may have only three
large flattened pustules which are distinctly of the pustulosa type. In
contrast, there may be several tubercles posteriorly as in Furtos’s species
with only a very few anterior ones as in Sharpe’s species. The size of
the tubercles also varies from heavy to practically indistinguishable. In
many of the collections it is possible to find individuals which would be
readily identified as P. pustulosa and some of which must be assigned
to P. globula. In collections where two or more slides are available, it
was found that upon initial examination of the material, the writer was
confused and often placed one slide in the pustulosa group and the other
slide in the globula group. This sorting was done upon the basis of the
nature of the tubercles.
It was thought by the writer that there might be some structure other
than the tubercles which would offer a definite and decisive criterion for
124 ILLINOIS BIOLOGICAL MONOGRAPHS
the separation of the species of Sharpe and that of Furtos. The writer
was unable to find any such criterion and was indeed unable to find any
correlation between the tubercles and the other variable characteristics
of the species. In comparing the description of P. globula and P. pustulosa
as given by Furtos (1933) the writer found the following differences,
each of which, upon proper examination, is found to have no specific
value in differentiating between the two described species:
(1) P. globula is said to measure 0.63 mm. in length and 0.41 mm.
in height; P. pustulosa measures 0.62 mm. in length and 0.45 mm. in
height. The writer has found that intermediates occur between these two
sizes and the differences in height as well as the length to height ratio
is not as large as the differences which occur in many of the more
definitely limited species of Cypria. The difference in height and length
to height ratio may then be dismissed as having no specific significance.
(2) For P. globula, Furtos gives 20 to 25 tubercles on the anterior
end and three large tubercles followed posteriorly by many small ones
at the posterior end; in P. pustulosa 12 to 17 tubercles at the anterior
end and two or three large pustules at the posterior end of the ventral
margin. As explained above, intergradations between the two described
forms occur.
(3) According to Furtos, the longer of the pair of terminal setae of
the third leg of P. globula is one and one-half times the length of the
ultimate podomere; the longer in P. pustulosa is but slightly longer than
the podomere. This difference is not at all significant as variation beyond
these limits is not uncommon in many ostracod species. Moreover, there
seems to be no correlation between the number of tubercles and the
relative length of the distal setae of the third thoracic leg.
(4) The furcae, according to Furtos’s descriptions, differ in some few
details in the two forms. In P. globula the furca is said to have a length
eleven times the least width of the ramus, while in P. pustulosa the length
is nine and one-half times the least width. If one assumes that camera
lucida drawings are more accurate than text descriptions, then it is ap-
parent by measuring the drawing (Furtos, 1933:pl. 16, fig. 6) that the
text description of the furca of P. globula is incorrect and the correct
length-width ratio is more nearly nine and one-half than eleven. One may
say then that there is no significant difference between the length-width
ratios of the furcal rami of the two forms under discussion.
(5) Another apparent difference between the descriptions of the two
species given by Furtos is that the dorsal seta of the furca in P. globula
is removed from the distal end of the ramus by one-third of the dorsal
margin of the ramus, while the dorsal seta of P. pustulosa is removed
from the distal end of the ramus by about two-fifths of the dorsal margin
of the ramus. Referring to Furtos’s drawing (her pl. 16, fig. 6) of the
OSTRACODS OF ILLINOIS—HOFF 125
furca of P. globula, it is apparent that the dorsal seta is removed from
the distal end of the ramus by at least two-fifths of the dorsal margin
of the ramus. This, then, is not a significant difference between the two
species.
(6) While Furtos states that the male structures are similar in P.
globula and P. pustulosa, she gives the size of the former as being 0.62
mm. long and 0.39 mm. high while the latter is 0.55 mm. long and
0.39 mm. high. Such size variation has no specific significance especially
since it is not correlated with any other characteristic.
The above discussion conclusively shows that the species P. globula
can be nothing else than the end of the series which represents P.
pustulosa. P. globula Furtos 1933 then becomes a synonym of P. pustulosa
(Sharpe 1897).
Whether or not there may be local races of individuals clustered about
one end of the series representing P. pustulosa is possible but not defi-
nitely known. The discovery and study of such races will not, the writer
believes, destroy our conception of P. pustulosa as it now stands, but
may add something to the knowledge of variation and species develop-
ment in the Ostracoda.
Ecology: In general, Physocypria pustulosa prefers the quiet waters
of lakes especially in areas where there is an abundance of plant life.
It is occasionally found in roadside ditches over apparently bare bottom
and is sometimes a constituent of plankton. The abundance of individuals
of this species seems to reach a peak in June with the individuals becom-
ing less abundant in July and August.
Distribution: P. pustulosa has been reported under the names P.
globula and P. pustulosa by Furtos (1933) from various places in Ohio.
Dobbin records it as Cypria (Physocypria) globula from Washington and
Alaska. It was reported from Illinois by Sharpe (1897) and Kofoid
(1908). It has been taken by the present writer in all parts of the state.
When sufficient collections have been made, records of the distribution
will probably be extended to all counties of the state.
Physocypria dentifera (Sharpe 1897) G. W. Miller 1912
Cypria dentifera Sharpe 1897. Sharpe, 1897:463-465, pl. 47, figs. 6-11; 1908:400, 410,
pl. 50, figs. 3, 4.
Cypria (Cypria) dentifera Sharpe 1897. Sharpe, 1918:820, figs. 1282a, b, c, d.
Physocypria dentifera (Sharpe 1897) G. W. Muller 1912. G. W. Miller, 1912:133;
Furtos, 1933:468.
Type Locality: Cincinnati, Ohio.
Description of the Male and Female (after Sharpe, 1897): Shell
highest just posterior to the center; anterior and posterior ends rounded,
126 ILLINOIS BIOLOGICAL MONOGRAPHS
the posterior more broadly. The ventral margin has a slight sinuation
near the center. The shell has dark brown markings distributed as fol-
lows: one anterior, one ventral, one ‘“dorsal-ventral,” and one vertical
just posterior to the eye. Few hairs except at the anterior and posterior
margins. “The anterior margin of the right valve projects as a hyaline
flange, receiving as in a pocket the anterior margin of the left valve,
which is armed with a row of eighteen to twenty tuberculiform teeth.”
Swimming setae of the second antennae reaching beyond the terminal
claws a distance equal to the entire length of the antennae. Second
thoracic legs stout; terminal claw much bent and as long as the last
three podomeres together; the distal seta of the antepenultimate podo-
mere two-thirds as long as the podomere. The two short setae of the third
thoracic legs are approximately equal to each other and to the last podo-
mere; the distal podomere has a sinuation on its inner edge and is two-
thirds as wide as long; penultimate podomere three and three-fourths
times the length of the terminal one, a plumose seta is found at its “middle
point” and a comb of bristles is located distally. The antepenultimate
podomere of the third thoracic leg as long as the penultimate; the rather
stout seta at the distal inner angle is as long as the seta on the penultimate
podomere. Caudal rami stout, about ten times as long as wide. Terminal
claw three-fifths as long as the ramus; subterminal one two-thirds as long
as the terminal one with a comb of long teeth near the tip. Terminal seta
equals one-half of the subterminal claw in length; dorsal seta not longer
than the least width of the ramus and located slightly above the center of
the ramus.
Remarks: The exact identity of Physocypria dentifera is somewhat
obscure as Sharpe seems to have been the only individual to see repre-
sentatives of this species. This species, as far as appendages are con-
cerned, bears a very close resemblance to Cypria maculata mihi. The
principal differences between Physocypria dentifera and Cypria maculata
are that the shell of the latter is smaller, the anterior margin of the left
valve is not tuberculate or crenulate, and the right valve has no hyaline
border. Occasionally individuals assignable to C. maculata may have a
roughened area along the margin of the left shell but never teeth in the
position, number, or shape shown by Sharpe (1897:pl. 47, fig. 6). It is
possible that Sharpe worked with material which showed a development of
this roughened margin into tubercles or Sharpe may have made an inaccu-
rate observation of the true condition. Like Furtos (1933), the present
writer has found no individuals assignable to Physocypria dentifera. Asa
result of a lack of material, it is impossible to compare in detail Physo-
cypria dentifera and Cypria maculata. When such material is available, it
OSTRACODS OF ILLINOIS—HOFF 127
may be possible to show that Physocypria dentifera and Cypria maculata
both belong to a series which represents a single species under the valid
name of Physocypria or Cypria dentifera Sharpe 1897.
Ecology: Nothing is known of the ecology of Physocypria dentifera
except that it was found in ponds by Sharpe (1908).
Distribution: Sharpe (1897) originally described this species from
Ohio. Later he (Sharpe, 1908) gave as new records New York and
New Jersey. In the same report (1908) but in the introduction, Sharpe
lists Illinois, Ohio, New York, and New Jersey as the localities from
which he had examined material in the U. S. National Museum. Nowhere
does he give any information concerning the locality from which the
Illinois material was taken. The present writer has found no individuals
of this species in his collections from Illinois.
SUBFAMILY ILYOCYPRINAE
Shell oblong to subrectangular, dorsal margin usually straight and hori-
zontal (figs. 99, 101) ; shell always possessing small pits, with one or more
transverse median depressions, often with larger rounded hump-like
projections and marginal spines. Antennules with some of the swimming
setae shortened and claw-like. Swimming setae of the antenna always
present, but may be greatly shortened. Antennae in male without special
setae. The endopodite of the first thoracic leg not strongly developed in
the female but consisting of two or three podomeres and clearly leg-like;
in the male larger and transformed into a prehensile palp of two podo-
meres; respiratory plate well developed with six setae. Ultimate podo- ~
mere of the third leg cylindrical with three setae, the longest of which
may or may not be reflexed. Furca always well developed. Ductus ejacu-
latorius with numerous, crowded chitinous rods and with spherical in-
flated opening at each end. Penis with a clearly twisted vas deferens.
A single genus Ilyocypris belongs to this subfamily. Daday in 1900
introduced a second genus Iliocyprella to include J. bradyi and related
species in which the swimming setae of the antennae are reduced and the
penultimate podomere of the second leg is divided. Species like J. gibba
with long swimming setae on the antenna and the third leg with the
penultimate podomere undivided were left in the genus Ilyocypris s. str.
Few writers have followed Daday’s division of the group. Among those
advocating this division is Sars (1928) who believes that Iliocyprella
should be retained as the differences between Iliocyprella and Ilyocypris
involve characters to which “generally a generic value has been assigned’”’
(Sars, 1928). However, the characters used for generic diagnosis vary
in different individual instances. The divided or undivided condition of
128 ILLINOIS BIOLOGICAL MONOGRAPHS
a podomere of a leg may occur in different species of the genus Candona
and yet assignment to that genus is not questioned. The relative length
of the swimming setae has little significance since considerable variation of
length of setae is shown within many genera. The general appearance
of the shell and appendages is so similar in Iliocyprella and Ilyocypris
and most of the useful taxonomically important structures are so alike
that there is little justification in accepting the genus Iliocyprella.
Genus ILYOCYPRIS Brapy anp Norman 1889
With the characters of the subfamily.
KEY TO SPECIES OF THE GENUS ILYOCYPRIS IN IEEING@IS
a. Shell with three pairs of distinct lateral projections (fig. 99-P) ; swimming
setae of antennae reach considerably beyond the end-claws; penultimate
podomere of the second leg undivided (leg of four podomeres) (fig. 100)
PS Pee HONORS DRE TI I. gibba (Ramdohr 1808) Brady and Norman 1889
b. Shell without well developed lateral projections, but with two shallow lateral
furrows on each valve (fig. 101); swimming setae of the antennae short,
almost claw-like; penultimate podomere of the second leg distinctly divided
(leg with five apparent podomeres) (fig. 102-P)............. I. bradyi Sars 1890
Ilyocypris gibba (Ramdohr 1808) Brady and Norman 1889
(Pl. VII, figs. 99, 100)
Cypris gibba Ramdohr 1808. Ramdohr, 1808:91, pl. 3, figs. 13, 14, 17.
Ilyocypris gibba (Ramdohr 1808) Brady and Norman 1889. Brady and Norman,
1889:107, pl. 22, figs. 1-5; Sharpe, 1908:410-411, pl. 56, figs. 1, 2; 1918:809, figs.
1257a, b; Furtos, 1933:427, pl. 1, figs. 4-7.
Type Locality: Europe.
Description of the Female: A species of the genus Ilyocypris. Shell
in side view (fig. 99) with the greatest height in the region of the eye and
almost equal to one-half the length. The dorsal margin nearly straight ;
ventral margin distinctly sinuated in the center. The anterior end ap-
pears larger and the margin more broadly rounded than the posterior. At
the anterior and posterior ends of the shell there are usually conspicuous
spines often set back from the margin. Three large lateral projections
are found on each valve (fig. 99-P): one slightly anterior to the center
of the shell and often coinciding with the muscle scars, the second dorsal
and posterior to the first, and the third and smallest ventral and posterior
to the center of the valve. These projections may be somewhat reduced
in a small percentage of individuals. Two furrows (fig. 99-F) lie dorsal
and anterior to the dorsal-anterior projection. These furrows are pos-
terior to the eye and extend to the dorsal margin of the shell. The
OSTRACODS OF ILLINOIS—H OFF 129
surface of the shell and the margins bear numerous hairs. From above,
the two most dorsal projections are easily observed on the sides of the
shell. The greatest width is less than the greatest height and is posterior
to the center of the shell. The length of the females vary greatly, the
average being a little less that 0.95 mm.
Swimming setae of the antennae well developed but variable; usually
the distal one-third of the setae extends beyond the end claws of the
antennae. Penultimate podomere of the second thoracic leg (fig. 100)
undivided, the leg being composed of four podomeres. Furcal ramus
stout; the ventral margin a little less than twelve times the least width
of the ramus; ramus gently curved with the dorsal margin spined. The
dorsal seta has a length approximately equal to four times the least
width of the ramus and is removed from the subterminal claw by a
distance nearly equal to the length of the seta. The terminal claw is
almost as long as two-thirds of the ventral margin of the ramus; the
subterminal claw is little shorter than the terminal. The terminal seta has
a length subequal to twice the least width of the ramus.
Description of the Male (mainly after Klie, 193Sa): The shell of the
male is said to be much like that of the female in shape and size. The
furca of the male is more strongly curved than in the female. The two
prehensile palps are similar; the propodus is long and cylindrical and the
long dactylus tapers to an acute point. The middle lobe of the penis is
much larger than the other lobes; it is lappet-like and the distal-inner
corner is in the form of a right angle. Males have been found in northern
Africa and in southeastern Russia. Males have not been reported from
North America and none were found in the present writer’s collections.
Remarks: The earliest reference to this widely distributed species in
North America is that of Sharpe (1908) who reported J. gibba from
Colorado. It seems rather strange that Sharpe (1897) did not find J. gibba
in Illinois when it is now known to be very abundant. That Sharpe did
not find this species in Illinois may be the result of examining little else
than material collected from ponds and lakes rather than rivers and
streams where it commonly occurs.
Ecology: I. gibba is a very common species found chiefly in running
waters. That it is seldom found in lakes and ponds is shown by its oc-
currence in such habitats in only three of the forty-four collections made
by the writer; the other forty-one collections were taken from streams,
rivers, and pools in stream beds. J. gibba is found for the most part
associated with vegetation and algae in current which, in some instances,
is very swift. This is in contrast to the habitat reported as “sandy
bottoms of large and small lakes” by Furtos (1933). It is possible that
few of her collections were made from streams since this type of habitat
130 ILLINOIS BIOLOGICAL MONOGRAPHS
is usually not considered profitable for collecting ostracods. Sars (1928)
reports J. gibba as being common in shallow ponds and “ditches with
clayey bottom.” Like most writers, Sars makes no mention of the occur-
rence in streams. G. W. Miller (1900), however, states that this species
is present in every little stream as well as the backwaters of rivers and
widened, shallow places in streams. It is found where the bottom mud is
not too slimy and soft. The waters in which /. gibba is found are usually
permanent but this species may at times be found in habitats, especially
small vernal streams, which completely dry up in July and August. In
consideration of the types of vegetation in the habitats from which this
species was collected, /. gibba is found most abundantly in grass growing
either in the water along the edge of the stream or growing on the bank
and falling over into the water. In about fifteen per cent of the col-
lections, J. gibba was found on the bare bottom and in about twenty-eight
per cent of the collections, this species was taken from algal masses.
In regard to seasonal distribution, /. gibba appears most abundant in the
late vernal and in the aestival seasons. It was not taken by the writer
earlier than May.
Distribution: I. gibba has been reported throughout the Holarctic
region. In the United States, it was first reported from Colorado by
Sharpe (1908). It has recently been recorded from Ohio by Furtos
(1933). The species is more abundant and widespread than generally
understood, having been taken by the present writer from counties in all
parts of Illinois but with greater frequency in the northern than in the
southern one-half of the state.
Ilyocypris bradyi Sars 1890
(PI. VII, figs. 101, 102)
Ilyocypris bradyi Sars 1890. Sars, 1890:59-60; Sharpe, 1908:411-412, pl. 56, figs. 3-6;
1918:810, figs. 1258a, b, c, d.
Ilyocypris bradit (sic!) Sars 1890. Furtos, 1933:428, pl. 1, figs. 8-10.
Type Locality: Norway.
Description of the Female: A species belonging to the genus Ilyo-
cypris. Subrectangular shell (fig. 101) with straight, almost horizontal,
dorsal margin. Greatest height in the region of the eye and scarcely more
than one-half of the length. Two distinct dorsal-lateral furrows are
present between the center of the shell and the eye. The dorsal margin
forms a corner with the posterior margin, giving the shell a rectangular
appearance. The anterior and posterior ends are rounded, the former
more broadly. The ventral margin has a conspicuous sinuation. From
above, the somewhat compressed shell is narrowly oblong in shape with
the anterior end pointed and the posterior end rounded, the left shell
OSTRACODS OF ILLINOIS—HOFF 131
slightly larger than the right, the sides of the valves flattened, and the
greatest width hardly two-fifths of the length. A few spines, tubercles,
and hairs decorate the margins. The shells of mature females usually
average about 0.95 mm. in length.
The length of the swimming setae of the antennae seldom reach
much beyond the middle, never beyond the distal margin, of the penulti-
mate podomere of the antenna. The second thoracic leg (fig. 102) has
five apparent podomeres through the division of the penultimate podo-
mere. The third thoracic leg of J. bradyi is similar to that of J. gibba but
the furca differs by the ramus of J. bradyi being much more curved, the
dorsal seta relatively smooth and straight, and the terminal seta little
exceeding the least width of the ramus. Otherwise similar to J. gibba.
Males: Concerning the males, Furtos (1933) says: “Male not re-
corded for Ohio. Rare elsewhere.” The present writer has found no
males in Illinois collections and knows of no instance in the literature
where males have been definitely recorded.
Remarks: As in the related species, J. gibba, Sharpe (1897) probably
overlooked the present species in Illinois because he did little collecting
from small streams.
Ecology: Like the closely related species, J. gibba, I. bradyi inhabits
running waters, seldom being found in ponds or lakes. Individuals are
also common in pools left in stream beds after the stream has ceased to
flow in late summer. The habitat of this species is similar in nearly all
respects to that of J. gibba, and in fact J. bradyi and J. gibba are often
found associated together.
Distribution: I. bradyi is known to be widely distributed in the Hol-
arctic region. It was first reported in the United States from Colorado by
Sharpe (1908). Furtos (1933) reports it from Ohio. The present
writer has taken J. bradyi from many counties in Illinois. The majority
of these counties are from the northern part of the state, none from the
extreme southern part.
SUBFAMILY ‘CYPRINAE s. ‘sir.
A subfamily of the family Cypridae. Shell usually reniform (figs. 105,
110); height variable but in most species about one-half of the length.
Swimming setae of the antennae (fig. 1-V) either well developed or
reduced, generally not reaching much beyond the end points of the termi-
nal claws. The outer masticatory process of the maxilla with two or
three spine-like setae; end podomere of the maxillary palp ordinarily
cylindrical, often narrowed or widened distally. First thoracic leg with
endopodite of one podomere in the female; modified in the male to form
a prehensile palp of two podomeres. Third thoracic leg distally beak-like,
132 ILLINOIS BIOLOGICAL MONOGRAPHS
modified for grasping; ultimate podomere with only two well developed
setae, the third being small and hook-like or wanting (fig. 1-T). Furca
usually well developed and having two claws and two setae with a
relatively slender ramus (figs. 107, 111).
The subfamily Cyprinae sensu lato as ordinarily used by many
authors may be broken into three subfamilies: the Cyprinae s. str., the
‘Notodrominae, and the Cypridopsinae. Following Kaufmann (1900b)
and Wagler (1937), the present writer has thought it convenient as well
as advisable to use the subfamily Cyprinae in the restricted sense. The
subfamily Cyprinae s. str. includes a number of genera. As the genera
are not properly limited or defined, each writer has used whatever ones
he thought convenient and applicable. Members of this subfamily are
found in nearly all parts of the world. The Cyprinae s. str. is repre-
sented in Illinois by a few species belonging to two genera: Cypricercus
Sars 1895 and Cyprinotus Brady 1885.
KEY TO GENERA OF THE SUBFAMILY CYPRINAE IN ILLINOIS
a. Margin of both valves of shell smooth (figs. 103, 105) ; the furcal ramus with
a length more than twenty times the least width (fig. 107)................
ROSS ste a ues ed bean Yet Mea a PRION Pani ach aust aye ek eae hes Saf Genus Cypricercus Sars 1895
b. Margin of right or left valve of shell tuberculated (fig. 110); the furcal
ramus with a length less than twenty times the least width (fig. 111)........
FOIE TPG Baie MER a tne keener ERE FEA IMIR SE I a Genus Cyprinotus Brady 1885
Genus CYPRICERCUS Sars 1895
Shell elongate, greatest height anterior to the center and in Illinois
species exceeding slightly one-half of the length. The outer masticatory
process with two long, toothed spine-like setae. Furca slender (fig. 107) ;
terminal claw with a length not more than one-half of the anterior margin
of the ramus but longer than three times the length of the terminal seta.
An important criterion of the genus is the coils of the testis in the anterior
portion of each valve (fig. 108-A). This important criterion, however,
cannot always be used since the males are in some species unknown,
in other species rare. The genus is found throughout the Holarctic region.
Since males are seldom seen in many species and are unknown in
others, the placing of any species into this genus depends largely upon
the character of the furca which has a ventral margin measuring more
than twenty times the least width of the ramus. According to Sars
(1928), who originally described the genus Cypricercus in 1895 to include
a South African species reproducing by syngamy and characterized by
a well developed furca and the peculiar coiled arrangement of the testes,
the genus should be expanded to include all the Cyprinae with the ex-
tremely long furcal rami even though the males may be unknown. Some
OSTRACODS OF ILLINOIS—HOFF 133
writers (as Furtos, 1933) choose to reserve the genus Cypricercus for
those species in which the males are well known and to place all forms
in which the males are either little known or unknown into the genus
Eucypris even though they are, because of the slender furcal rami,
closely related to Cypricercus. Such a system based on the method of
propagation is very artificial and is certainly not the method indicated
by Sars, the original designator of the genus Cypricercus.
Pee TO SPECIES OF THE GENUS CYPRICERCUS IN: ILLINOIS
la. Shell tuberculate over entire surface (fig. 103); usually under 1.00 mm. in
[STC E D0 6.4 BCS ae Oe eRe ore eS C. tuberculatus (Sharpe 1908) comb. nov.
2a. Size of shell of female usually more than 1.35 mm. in length; penultimate
podomere of the antenna narrow, six times as long as wide, the seta which
arises from the distal, posterior corner of the antepenultimate podomere
widened at the base but not forming a spherical-shaped swelling; dorsal
seta of the furca reaching only to base of the subterminal claw............
ne nec OAS OO BIND OTS eve a eer aen ae aera C. fuscatus (Jurine 1820) Sars 1928
b. Size of shell usually less than 1.35 mm. in length; penultimate podomere
of antenna only four and one-half times as long as the width (fig. 1-AN),
base of seta at the distal posterior corner of the antepenultimate podomere
usually swollen spherical-shaped (fig. 106-B); dorsal seta of the furca
reaches beyond the base of the subterminal claw (fig. 107)..............
32990 25 SOD OO IER NOI CIOS Ra SE IE econ arcane C. reticulatus (Zaddach 1844) Sars 1928
Cypricercus tuberculatus (Sharpe 1908) comb. nov.
(Pl. VII, figs. 103, 104)
Spirocypris tuberculata Sharpe 1908. Sharpe, 1908:406-408, pl. 50, figs. 1, 2; pl. 54,
fig. 4; pl. 55, figs. 1-6; 1918:814, figs. 1267a, b, c.
Type Locality: Jackson Park, Chicago, Ilinois.
Description of the Female: A species of the genus Cypricercus. Seen
from the side (fig. 103), the shell is almost elliptical; the dorsal margin
is a flattened arch which, along with the almost straight ventral margin,
makes both ends appear broadly and evenly rounded, the anterior more
so than the posterior. The greatest height lies near the center of the
shell and is approximately four-sevenths of the length. From above, the
shell is oval and very tumid; the valves are nearly the same size but the
right, according to Sharpe (1908), may overlap slightly the left. In some
individuals, however, the present writer has found that the left valve
is the larger and overlaps the right valve at least anteriorly. The surface
of the shell is covered with characteristic droplet-like papillae which are
strikingly conspicuous. Most of the papillae bear fine hairs. The color
is usually purplish brown with a light transverse band in the region of
the eye and another light band near the posterior one-third of the shell.
Usually there is a much darkened area between the two light colored
134 ILLINOIS BIOLOGICAL MONOGRAPHS
bands. Sharpe (1908) gives the shell dimensions as follows: length,
0.93 mm. ; height, 0.53 mm.; breadth, 0.7 mm. Most of the writer’s speci-
mens measure 0.86 to 0.90 mm. in length and 0.49 to 0.51 mm. in height.
The swimming setae of the antennae extend but little beyond the ends
of the terminal claws. The outer masticatory process of the maxilla has
two claw-like toothed spines, one of which may be much more heavily
toothed than the other. The pectinate claw of the second thoracic leg has
a length equal to one and one-third times the sum of the lengths of the
last three apparent podomeres of the leg. Furca nearly straight, slender
as in other members of the genus Cypricercus. According to Sharpe
(1908) the ratio of the length to the least width of the furca in C.
tuberculatus is 32 to 1. This statement is not supported by his figure
(1908:pl. 55, fig. 3) and it cannot be verified by the present writer who
has found the ratio of the length of the ventral margin of the furca to the
least width to be about 22 or 23 to 1. The dorsal margin of the furca
is smooth. The dorsal seta is relatively short, reaching only to the base
of the subterminal claw and being removed from the tip of the ramus
by a distance equal to about twice the least width of the ramus. The
terminal claw is nearly straight, obscurely pectinate near the distal end,
and measuring approximately one-half the length of the dorsal margin of
the furca; the subterminal claw is nearly four-fifths as long as the
terminal one. The terminal seta is longer than the dorsal one, measuring
about one-third as long as the terminal claw or over four times the least
width of the ramus.
Description of the Male: The shell of the male is similar in size,
shape, and sculpturing to that of the female. The appendages of the
male are like those of the female. The prehensile palps have a stout
propodus with a falciform dactylus. The dactylus of the right palp is
larger than that of the left but somewhat similar in shape. The testes
have their origin in the anterior one-half of the valves, where they
occur as concentric circular figures. The ductus ejaculatorius is long and
slender and has about twenty wreaths of supporting spines. The penis
(fig. 104) has the middle and inner lobes well developed. The inner lobe
is distally rounded while the middle lobe is truncate and extends beyond
the end of the inner lobe.
Remarks: Cypricercus tuberculatus when described in 1908 was as-
signed by Sharpe (1908) to the genus Spirocypris which the same writer
(1903) had previously created. Since the arrangement of the testes in
Cypricercus is similar to that found in Spirocypris and the nature of the
testes was the chief diagnostic character of Sharpe’s genus Spirocypris,
there is no valid reason for not absorbing his genus into the previously
designated genus Cypricercus. The advisability of assigning the species
OSTRACODS OF ILLINOIS—HOFF 135
under discussion to the genus Cypricercus is substantiated by the placing
of a very closely related species in the genus Cypricercus by Sars (1926).
Sars at this time seems to have been unaware of the Spirocypris
tuberculata of Sharpe as he says (Sars, 1926) regarding his new species,
Cypricercus horridus Sars 1926, from Canada: “It is, however, well dis-
tinguished from any of the other known species by the very pronouncedly
scabrous surface of the shell.” Both C. tuberculatus and C. horridus
seem to fit naturally into the genus Cypricercus because of the character
of the furca and the arrangement of the testes. C. horridus differs from
C. tuberculatus in having a shell of greater length, more overlapping of
the right valve by the left, a more slender penultimate podomere of the
antenna, and a furca in which the dorsal seta is much longer than the
terminal one and which extends well beyond the tip of the ramus.
Ecology: Sharpe (1918) reports this species under the name Sp1-
rocypris tuberculata in “Shallow, weedy, and swampy ponds; spring.”
The present writer has taken this species in June from grass and algae
along lake shores and from a swampy area in a small lake where there
were both decaying and living plants over a mud bottom. Collections
made from the same locality in August by Mr. Bertrand A. Wright and
by the writer did not reveal the presence of this species.
Distribution: This species was reported as common by Sharpe (1908)
from northeastern Illinois and northern Indiana. The present writer has
taken the species only from McHenry and Lake Counties, Illinois. As
far as known at the present time, C. tuberculatus appears to be restricted
in habitat to the region of lakes of glacial origin in the Chicago area.
Cypricercus fuscatus (Jurine 1820) Sars 1928
Monoculus fuscatus Jurine 1820. Jurine, 1820:174, pl. 19, figs. 1, 2.
Cypris burlingtonensis Turner 1894. Turner, 1894:17-19, pl. 7, figs. 14-23.
Cyprinotus burlingtonensis (Turner 1894) Turner 1895. Turner, 1895:333-334, pl.
70, figs. 14-23; Sharpe, 1897:435-437, pl. 42, fig. 7; Furtos, 1933:446-447.
non Cypris fuscata Turner 1895 (non Jurine 1820). Turner, 1895:320-321, pl. 71,
figs. 41-46; pl. 72, figs. 7-7p; pl. 76, fig. 9.
Cypris (Cypris) fuscata (in part) (Jurine 1820) Desmarest 1825. Sharpe, 1908:
403-405, pl. 53, fig. 3, non 1, non 2, non 4.
Cypris (Cyprinotus) burlingtonensis Turner 1894. Sharpe, 1918:816, figs. 1272a, b, c.
Cypris (Cypris) fuscata (in part as var. major G. W. Miller 1900) (Jurine 1820)
Desmarest 1825. Sharpe, 1918:818, fig. 1278a, non b, non c, non d.
non Eucypris fuscata (Jurine 1820) var. gigantica Furtos 1933. Furtos, 1933:451-
452, pl. 4, figs. 1-4.
Type Locality: Europe.
Description of the Female (chiefly after Khe (1938a)): An ostracod
of the genus Cypricercus. Shell in side view elongated; greatest height
136 ILLINOIS BIOLOGICAL MONOGRAPHS
just posterior to the eye and more than one-half the length. The dorsal
margin forms a flat arch which passes into the broadly rounded anterior
margin and the narrowly rounded posterior margin without interruption.
Ventral margin usually showing a very slight sinuation. From above, the
shell is oval; the greatest width in the middle and more than one-half
of the length of the shell; the posterior end is rounded and the anterior
is weakly pointed. Length of the shell usually between 1.4 mm. and
1.5 mm.
The swimming setae of the antennae reach beyond the distal ends of
the terminal claws. The penultimate podomere of the antenna has a
length equal to six times the width; posterior distal seta of the ante-
penultimate podomere has a tapering base. The claw-like setae of the
outer process of the maxilla are toothed. The ramus of the furca is very
narrow, the ventral margin having a length equal to twenty-five times the
least width of the ramus. The terminal claw has a length less than one-
half of the ventral margin of the ramus and the dorsal seta reaches only
to the base of the subterminal claw.
Male: Unknown.
Remarks: Sharpe seems not to have recognized C. fuscatus as such
in 1897 but he (1897) described some individuals which no doubt be-
longed to this species under the designation Cyprinotus burlingtonensis
(Turner 1894) Turner 1895. At the same time, Sharpe apparently ap-
plied the name Cypris fuscata to what herein is designated as Cypricercus
reticulatus. The exact identity of the Cypris burlingtonensis of Turner
(1894) appears to have been for some time in doubt, so much in fact that
G. W. Miller (1912) in the volume on ostracods in “Das Tierreich”
series listed it under the heading “Genera dubia et species dubiae Cy-
prinarum.” At the time of the original description of Cypria burlington-
ensis by Turner, the descriptions of the now designated Cypricercus
fuscatus from Europe (type locality) were so confused with other related
species that he may readily have been unable to establish identity with
the European fuscata. Thus he was forced to describe his material
as a new species. The mere creation of a synonym would not have created
much disturbance but Turner later (1895) changed his species burling-
tonensis from the genus Cypris to the genus Cyprinotus. This may or
may not have been correct at that time as the original diagnosis of the
genus Cyprinotus as given by Brady (1885) was very inadequate. This
incomplete generic diagnosis may have led Turner to assign his burling-
tonensis to the genus Cyprinotus. The genus Cyprinotus has since then,
however, been emended and accepted by most authors to include species
which like the type species, Cyprinotus cingalensis Brady 1885, has a
OSTRACODS OF ILLINOIS—HOFF 137
row of denticles along the margin of the right valve, or in some species
along the margin of the left valve. Evidently both Turner (1895) and
Sharpe (1897) accepted the genus Cyprinotus without reference to the
denticles of the valve margin. Sharpe (1897), however, seems to have
noticed something peculiar about burlingtonensis since he is led to state
that it “greatly resembles Cypris fuscata Jurine in many respects.”
Furtos (1933) continued to carry burlingtonensis without question in the
genus Cyprinotus although she saw no ostracods in Ohio assignable to
this species and even states (1933) that no mention was made by Turner
of marginal tubercles. At the same time she gives as a characteristic of
the genus Cyprinotus (Furtos, 1933) that the margin of the right valve
is more or less tuberculated. Certainly there are no tubercles on the
margin of the valves in Turner’s Cypris burlingtonensis. According to
recent generic diagnosis, this cannot belong to the genus Cyprinotus.
Both the nature of the shell and the form of the furca indicate a close
relationship with species of the genus Cypricercus. Thus burlingtonensis
must be placed in the genus Cypricercus. Once this is done, it is obvious
that burlingtonensis agrees in practically every respect with Cypricercus
fuscatus, especially when a close study is made of Turner’s illustrations
(Turner, 1894:pl. 7, figs. 14-23). Not only is the identity shown by the
morphological structure but some substantiation of this synonymy is of-
fered by ecological data since both C. fuscatus Jurine and Turner’s Cypris
burlingtonensis are vernal species found usually in temporary pools where
the animals live in the decaying vegetation of the previous summer. On
the basis of the above arguments, there can be no doubt that Cyprinotus
burlingtonensis (Turner 1894) Turner 1895 must become a synonym of
Cypricercus fuscatus (Jurine 1820) Sars 1928.
In regard to Eucypris fuscata var. gigantica described by Furtos in
1933, it is definitely not equivalent to C. fuscata from which it differs in
many important respects. On the basis of these differences, the present
writer holds the opinion that gigantica should be raised from subspecific
to specific rank.
Sharpe (1908, 1918) did not differentiate very clearly between the
now designated Cypricercus fuscatus (his Cypris fuscata var. major
G. W. Miller 1900) and the herein designated Cypricercus reticulatus
(his Cypris fuscata var. minor G. W. Miller 1900), although he did
recognize that the two different forms occurred. His drawings are often
of the minor variety (C. reticulatus) but labeled as being of the major
variety (C. fuscatus). This is unfortunate and shows perhaps that he was
unable to distinguish clearly between the now designated species C. reticu-
138 ILLINOIS BIOLOGICAL MONOGRAPHS
latus and C. fuscatus. The following table is designated to facilitate
separation of these two closely related species:
C. fuscatus (Jurine
Shell: 1820) Sars 1928
SIZE; MEMAIE. 40.5.0 os aut ach weleipute 1.4-1.5 mm. long
Dorsalemancin= so eee te Flat, even arch
ROMA WOVE ce cs wee eee seme ve ee Anterior end more
acute than pos-
Antenna: Benes
Penultimate podomere.............. Length six times
the width
Posterior distal seta of antepenulti-
mate podomere................ Tapering basal
Buea: portion
Ratio of length to least width of ramus 25:1
Wrorsal Seta) sud g ee ete ne Scarcely reaches
beyond base of
subterminal claw
Merminaliclawaeee ene eon eee Shorter than one-
half of ventral
margin of ramus
M@erminal Setasy usec. ote oes Length less than
one-third of sub-
terminal claw
C. reticulatus (Zaddach
1844) Sars 1928
1.0-1.3 mm. long
Rounded, obtuse angle
at highest point
Both ends equal in
shape
Length four and one-
half times the width
Spherical basal
portion
Dea
Extends beyond the
base of the subter-
minal claw
Nearly equals one-
half of ventral
margin of ramus
Length more than one-
third of subterminal
claw
Ecology: Cypricercus fuscatus is found in grassy ponds and swamps
both in North America (Turner, 1894; Sharpe, 1908) and in Europe
(Klie, 1938a). This species has but a single generation each year. Indi-
viduals may be found in the prevernal, vernal, and early part of the
aestival season in Illinois,
Distribution: C. fuscatus is found throughout the Holarctic region.
It was reported as Cypris burlingtonensis by Turner (1894) from Burl-
ington, Ohio; Atlanta, Georgia; and Kent County, Delaware. Under the
same designation, Sharpe (1897) reported this species from Normal,
Illinois. Later Sharpe (1908) reported this species as Cypris fuscata
var. major from the region of Chicago, Illinois, and the northwestern
corner of Indiana. Shelford (1913) lists Cypris fuscata Jurine as
occurring in a temporary pond south of Jackson Park, Chicago, Illinois.
Sharpe, according to a personal conversation with Dr. V. E. Shelford,
identified this material and the present writer believes that it may have
included both Cypricercus fuscatus and C. reticulatus. The writer has
not discovered individuals of this species in his collections but this may
be expected as no early spring collections were made from the region
immediately southeast of Chicago, Illinois, where this species appears to’
be more or less localized as far as the state of Illinois is concerned.
OSTRACODS OF ILLINOIS—HOFF 139
Cypricercus reticulatus (Zaddach 1844) Sars 1928
(Plots fied». pl: Vil, fis 105:
pl. VIII, figs. 106-109)
Cypris reticulata Zaddach 1844. Zaddach, 1844:34; Sharpe, 1897:441-442, pl. 43,
figs. 3, 4.
Cypris affinis S, Fischer 1851. S. Fischer, 1851:160, pl. 10, figs. 9-11.
Cypris fuscata Sharpe 1897 (non Jurine 1820). Sharpe, 1897:442-443, pl. 43, fig. 5.
Cypris testudinaria Sharpe 1897. Sharpe, 1897:444-445, pl. 44, figs. 1-4.
Cypris (Cypris) fuscata (in part) Sharpe 1897 (non Jurine 1820). Sharpe, 1908:
403-405, pl. 53, figs. 1, 2, 4, non 3.
Cypris (Cypris) fuscata (in part as var. minor G. W. Miller 1900) Sharpe 1897
(non Jurine 1820). Sharpe, 1918:818, fig. 1278b, c, d, non a.
Eucypris affinis hirsuta Furtos 1933 (non Fischer 1851). Furtos, 1933:450-451, pl. 2,
figs. 9-11, 16.
Type Locality: Germany.
Description of the Female: An ostracod’of the genus Cypricercus.
In side view (fig. 105), the shell appears subtriangular with the height
considerably greater than one-half of the length. The greatest height
lies anterior to the middle where the dorsal margin forms a rounding,
obtuse angle. Both the anterior and posterior slopes of the dorsal margin
are equally slanted and pass without interruption into the margins of the
two ends. The anterior end is more widely rounded than the posterior.
The ventral margin shows a slight sinuation. Viewed from above, the
shell appears broadly elliptical with the greatest width in the center of the
shell and more than one-half the length. The ends are somewhat obtusely
rounded, neither being acutely pointed. The length of the shell varies,
individuals occasionally being as small as 1.00 mm. or as large as 1.30
mm. The young of this species bears characteristic shell sculpturing
regarding which Zaddach (1844) in his original description of Cypris
reticulata says: “Superficies lineis reticulatis et quasi insculptis ornata est,
colore olivaceo, maculis nigricantibus.” The shell of the adult is not
sculptured.
The swimming setae of the antennae extend beyond the ends of the
terminal claws. The penultimate podomere of the antenna has a length
only four and one-half times the width; the posterior distal seta (fig.
106-B) of the antepenultimate podomere has a spherical basal portion.
The claw-like setae of the outer masticatory process of the maxilla are
toothed. The ventral margin of the furcal ramus (fig. 107) has a length
twenty-two times the least width of the ramus. The terminal claw is
equal to one-half of the length of the ventral margin of the ramus. The
distal end of the dorsal seta reaches beyond the base of the subterminal
claw and the terminal seta is considerably longer than the dorsal one.
140 ILLINOIS BIOLOGICAL MONOGRAPHS
Description of the Male: A single male specimen assignable to this
species was available for study. This specimen was in poor condition,
having been preserved for over forty years as a part of the collection of
material in the “Field Zoology” Laboratory at the University of Illinois.
The shell (fig. 108) is very flexible and thin, being little calcified. The
surface of the valves are covered with fine hairs. The general shape is
similar to that of the female. The testes (fig. 108-A, P) may be seen
readily through the surface of each valve. In addition to the part of the
testis always found in the posterior part of each valve, there is in this
species an extension in the form of whorls in the anterior one-half of
each valve. The appendages of the male are similar to those of the
female. The prehensile palps offer no specific distinction. The ductus
ejaculatorius is elongated and cylindrical with more than thirty whorls
of spines. The penis (fig. 109) has a substantial inner lobe with a
broadly rounded distal end; the middle lobe is thin and falciform in
shape with the distal point directed toward the inner edge of the penis.
In the writer’s single specimen, a thin very much reduced flap may be
distinguished on the outer edge of the penis. Whether or not this is
actually the rudiments of an outer lobe cannot be determined with cer-
tainty because of lack of material. Alm (1914:pl. 1, fig. 3) shows no such
outer appendage. The size of the male as given by Alm (1914) is 1.1
mm. to 1.2 mm. in length and the dimensions given for Cypris testudinaria
by Sharpe (1897) is 1.15 mm. in length, 0.74 mm. in height, and 0.65 mm.
in width. The length of the individual in the present writer’s collection
exceeds slightly 1.3 mm. in length but since the shell is very flexible and
has been much flattened and distorted in mounting, this size certainly far
exceeds the actual length in the undamaged animal.
Males are seldom seen in most collections and seem, indeed, to be
more common in the colder parts of the range of this species. Sharpe
(1908) reported, under the designation Cypris fuscata var. minor, the
males as common in the Chicago region. Alm (1914) mentions under the
name Eucypris affinis hirsuta Fischer (E. fuscata minor G. W. Miller)
the presence of males in Newfoundland, Greenland, and Siberia.
Remarks: Cypricercus reticulatus (Zaddach 1844) is a variable species
which has caused considerable confusion in the literature as a result of
the morphological variation between young and adult and male and
female. Much confusion has also been occasioned by the inability of
investigators to separate this species from closely related species because
the minute details of structure used in the differentiation were until
recently unknown or misunderstood.
It is unfortunate that the name delegated to the young of this species,
reticulatus, by Zaddach (1844) has not been retained by recent writers
OSTRACODS OF ILLINOIS—HOFF 141
on this group. For a number of years it was thought to be a species
separate from the adult described by Fischer in 1851 under the name
Cypris affinis. Sharpe (1897) did not realize that he had the young and
mature of the same species and so continued to designate them separately.
The sparsity of collections which contain both young and mature indi-
viduals contributed to the inability of recognition of the young which are
characterized by a shell sculpturing lacking in the adult. Since there is a
single generation each year and the transition from the “reticulatus’’ to
the “‘affinis” type appears to take place more or less simultaneously in
individuals of a given population, young and mature individuals are
seldom found in the same collection.
The present writer is certain that he has the Cypris reticulata de-
scribed by Zaddach and he is also certain that it is the young of the
Cypris affinis of Fischer. European writers as Sars (1928), Wagler
(1937), and Klie (1938a) give reticulatus as an unquestioned synonym
of affinis. These same writers, however, continue to use the name affinis
in spite of the fact that reticulatus has priority and should be the valid
designation for this species. Sars (1928) states his reason for not using
the earlier name, reticulata, as follows: “The specific name reticulata
proposed by Zaddach and assigned by some recent authors to this species
must, I think, be wholly discarded, as only applying to immature speci-
mens.” Such neglect of the name reticulata is in direct contradiction to
that part of the International Rules of Zoological Nomenclature which
reads as follows: “ArticLe 26. The Law of Priority obtains and con-
sequently the oldest available name is retained: .... (b) When any
stage in the life history is named before the adult.” Unfortunately then,
Cypricercus reticulatus must replace C. affinis as the valid name for the
species under consideration.
Besides separately naming the young and adult of C. reticulatus,
Sharpe (1897) apparently also named the males, designating them as a
new species, Cypris testudinaria. Even though there is much similarity
between males and females, Sharpe seems not to have recognized the
identity of his male specimens. The reason for establishing a new species
for the males was probably that the males of the now designated C. retic-
ulatus were unknown in the literature at the time of Sharpe. In fact,
Sars recently (1928) reported the males as unknown in spite of the fact
that Alm described males as early as 1914. The description given by
Sharpe (1897) for Cypris testudinaria agrees favorably with the descrip-
tion of males given by Alm (1914) under the designation Eucypris
affinis hirsuta. As far as the Cypris testudinaria of Sharpe is concerned,
his description is evidently based entirely upon male specimens for he
particularly stresses the nature of the ductus ejaculatorius (Sharpe, 1897)
but nowhere refers to the females.
142 ILLINOIS BIOLOGICAL MONOGRAPHS
The designation Cypris fuscata which Sharpe (1897) used for the
species under discussion was certainly an error on his part resulting
apparently from the inavailability of good descriptions of the closely
related European species belonging to the genus Cypris. At the time of
Sharpe, the exact identification of many of the European species of the
genus Cypris was in doubt and no two authors agreed on the valid name
or the identity in many of the species.
While Cypricercus fuscatus and C. reticulatus are closely related,
there are several differences in structure upon which differentiation be-
tween species can be based. These structures were undescribed in early
literature but are now well known and may be applied toward straight-
ening out the synonymy of C. fuscatus and C. reticulatus. A comparison
of the morphological differences separating C. fuscatus and C. reticulatus
is given in the “remarks” under the description of the former. In spite
of the fact that Sharpe in 1897 did not mention most of the structures
now used as a basis for separation of C. fuscatus and C. reticulatus,
there are certain minor differences such as shell shape, the general shape
of the furca, and the relative lengths of the setae and claws of the furca,
which clearly indicate that many of Sharpe’s figures (1897:pl. 43, fig. 5;
1908:pl. 53, figs. 1, 4; 1918:figs. 1278c, d) illustrating his C. fuscatus
are drawn from species assignable to C. reticulatus rather than to
C. fuscatus.
Other writers besides Sharpe have been confused over the proper
designation of this species. Furtos (1933) was aware that Sharpe’s
fuscata of 1897 was not the true fuscata of Jurine, and yet she un-
fortunately adopted Alm’s designation of this species, Eycypris affinis
hirsuta (Fischer), rather than the more nearly correct Cypricercus affinis
as used by Sars and other European writers. It is now generally known
that Alm (1916) made an error in assigning hirsuta as a subspecies of
affinis for the two forms differ specifically in many ways. Chief among
these differences (Klie, 1938a; Sars, 1928) is the smooth nature of the
claws of the outer masticatory process in C. hirsuta and the toothed
condition in C. affinis. The individuals described by Furtos (1933) were
characterized by having toothed claws on the outer masticatory process
and so cannot belong to the species C. hirsutus (Fischer 1851) Sars 1928.
Ecology: C. reticulatus is typically a species of vernal ponds. Very
rarely it may be found along the edge of pools in vernal streams where
there remains decaying grass from the previous growing season. It is
associated with live and dead grass and algae. There appears to be a
single generation each year.. The young appear in the prevernal season
before the ice has completely disappeared. The juveniles are characterized
OSTRACODS OF ILLINOIS—HOFF 143
by a reticulated sculpturing on the shell and may be found not later than
the last of April at the latitude of Urbana, Illinois. Beginning with the
first of May, only individuals lacking the sculpturing and therefore con-
sidered to be approaching maturity may be found. The eggs survive the
drying up of the pond during the serotinal season and hatch at the end of
the haemal season. Such a life cycle is also shown by Alm (1916) for
this species under the designation Eucypris affinis hirsuta in Europe.
Distribution: Cypricercus reticulatus is common throughout the
Holarctic region. Under the designation Eucypris affinis hirsuta, Alm
(1914) described it from the Arctic region of North America. Sharpe
(1897) reported it under a variety of names from Illinois, chiefly from
the east central part of the state. Later (1908) he reported it from the
Chicago region. In the writer’s collections are specimens taken in March,
1940, from a pond near Reelfoot Lake, Tennessee, by Mr. Robert Yapp.
The writer has this species in a collection made by Mr. F. R. Cagle in
Jackson County, Illinois. This material was given the present writer by
Dr. Victor Sprague who received it from Mr. Cagle. The writer has
collected individuals of C. reticulatus from the following counties in
Illinois: Champaign, Piatt, Vermilion, and Woodford.
5 GeNus CYPRINOTUS Brapy 1885
Form of shell variable, greatest height equal to or greater than one-
half the length. The dorsal margin may be evenly arched or may have an
obtuse apex (fig. 110). Valves commonly unequal; either the right or
left valve may be the longer. Margin of one valve ornamented with small
tubercles along part or all of the free margin; the margin of the other
valve smooth. Swimming setae of the antennae well developed. The
outer masticatory process of the maxilla with two claw-like setae which
may or may not be toothed. Furca (fig. 111) moderately developed, the
dorsal seta commonly longer than the terminal seta and located close to
the subterminal claw. The terminal claw of the furca is longer than one-
half the length of the ventral margin of the furcal ramus. The genus
Cyprinotus is practically cosmopolitan. Two species are known from
Illinois.
KEY TO SPECIES OF THE GENUS CYPRINOTUS IN ILLINOIS
a. Left valve of shell larger than the right valve; dorsal seta of furca with a
length about equal to one and one-half times the length of the terminal seta
Circe UP) Vs fee ee ic) toc Sersiomie hee eee C. incongruens (Ramdohr 1808) Turner 1895
b. Left valve of shell smaller than the right valve; dorsal seta of the furca
has a length equal to about twice the length of the terminal seta...........
Tne A OOO OIE RROD ACE COOTER TST TREAT PEE ae C. pellucidus Sharpe 1897
144 ILLINOIS BIOLOGICAL MONOGRAPHS
Cyprinotus incongruens (Ramdohr 1808) Turner 1895
(PE Vil, hes: 110; ah)
Cypris incongruens Ramdohr 1808. Ramdohr, 1808:86, pl. 3, figs. 1-12, 15, 18-20;
Turner, 1893:8, pl. 2, figs. 17-21.
Cyprinotus incongruens (Ramdohr 1808) Turner 1895. Turner, 1895:330-331, pl. 68,
figs. 9-16.
? Cyprinotus pellucida Sharpe 1897. Sharpe 1897:434-435, pl. 42, figs. 1-6.
Cypris incongruens Ramdohr 1808. Sharpe, 1908:405-406, pl. 54, figs. 1-3.
Cypris (Cyprinotus) incongruens Ramdohr 1808. Sharpe, 1918:815, fig. 1270a, b,c, d.
Cyprinotus incongruens incongruens (Ramdohr 1808) Turner 1895. Furtos, 1933:
447-449, pl. 4, figs. 8-12.
Type Locality: Europe.
Description of the Female: An ostracod of the genus Cyprinotus. In
side view (fig. 110), the right shell is elongated, highest just posterior to
the center, the greatest height being about three-fifths of the length. The
dorsal margin is arched and often has a slight sinuation just anterior or
posterior or both anterior and posterior to the apex in at least one of the
valves. The ventral margin has a slight sinuation in the center. In a
view from above, the left valve overlaps the right. The shell is widest
at its posterior one-third; anterior more acutely pointed than the
posterior. The greatest width is about eighty-five per cent of the greatest
height. The anterior and the ventral-posterior margins of the right
valve are ornamented with a row of tubercles. The margins of the left
valve are smooth. The length of the shell of the adult varies from 1.4
to 1.75 mm. and the color varies from a yellow to a brownish-yellow.
The natatory setae of the antennae extend beyond the tips of the
terminal claws; the claw-like setae of the outer masticatory process of
the maxilla are toothed. The furca (fig. 111) is stout, slightly bowed,
with the terminal claw having a length about one-half the length of the
dorsal margin of the furcal ramus. The length of the ventral margin of
the furca is about eleven times the least width of the furca. The terminal
seta has a length about one-half to two-thirds the length of the sub-
terminal claw of the furcal ramus; the dorsal seta has a length about one
and one-half times the length of the terminal seta and is removed from
the subterminal claw by a distance equal to little more than the least
width of the ramus. The subterminal claw measures approximately two-
thirds the length of the terminal one.
Description of the Male (after Klie, 193Sa): The present writer has
found no males in his collections from Illinois. In the shell of the male,
the greatest height lies in the middle. The shell is smaller than that of
the female, measuring usually about 1.2 mm. in length. The prehensile
palps are dissimilar and unequal; the right palp has a heavy propodus
and the dactylus is swollen, being falciform and tapering gradually to a
OSTRACODS OF ILLINOIS—HOFF 145
blunt distal point; the left palp has a dactylus which is recurved and
slender, having an even width throughout about the distal two-thirds of
its length. The penis has only two lobes; the inner lobe is short and
has a wide subtruncate distal margin; the middle lobe which extends
distally beyond the inner is triangular in shape and the blunt point is
directed toward the inner margin of the penis. The males are not common
in many localities.
- Remarks: This species was first reported from North America by
Turner who included with his description drawings (1893:pl. 2, figs.
17-21) sufficiently accurate to allow verification of his determination.
G. W. Miiller (1912) questions Turner’s identification of this form as
expressed by the latter in 1895. Turner’s drawings in 1893 are much
better than those in 1895 and certainly Miller was justified in his
criticism of the 1895 determination.
There is a possibility that C. pellucidus Sharpe 1897 (Sharpe, 1897,
1903) may be a species based on immature individuals of C. incongruens.
Sharpe’s drawings of the shell of C. pellucidus never show the gonads
indicative of a mature animal. A discussion of this possible synonymy is
given under the “remarks” in the description of C. pellucidus.
Ecology: Sharpe (1918) gives the habitat of this common species as
“temporary ponds and watering troughs.” Furtos (1933) reports it from
a rock-pool along the shore of Lake Erie in Ohio. It is the general
consensus of opinion among European workers (Alm, 1916; Sars, 1928;
et al.) that this species is found in puddles, ponds, and ditches. The
present writer has taken it more times from running waters than he
has from temporary ponds and ditches. Not only is this species found
along the edge in grass and vegetation of shallow, quiet waters but it
may be taken from masses of algae which hang in swiftly running water.
The kind of bottom seems to have no significance as individuals may be
found equally abundant over sand as over mud bottom. The writer’s
collections were made in the aestival season but whether or not this gives
any information upon the seasonal occurrence may be doubted especially
since Alm (1916) found this species abundant throughout most of the
year in Sweden.
Distribution: Cyprinotus incongruens is cosmopolitan except that it
has not been reported from Australia (Klie, 1926a). In North America,
it was reported first from Ohio by Turner (1893) and then by Furtos
(1933). Sharpe (1897) reported it from Florida and later (1908) from
Pennsylvania. Alm (1914) found it in material from Greenland, and
Dobbin (1941) has reported it from Oregon. The present writer has
found it in collections from several counties in the northern one-half of
Illinois. It has not been found in the southern part of the state.
146 ILLINOIS BIOLOGICAL MONOGRAPHS
Cyprinotus pellucidus Sharpe 1897
Cyprinotus pellucida Sharpe 1897. Sharpe, 1897:434-435, pl. 42, figs. 1-6.
Cypris pellucida (Sharpe 1897) Sharpe 1903. Sharpe, 1903:988-989, pl. 68, figs. 1-5;
Weckel, 1914:178, figs. 7, 8.
Cypris (Cyprinotus) pellucida (Sharpe 1897) Sharpe 1903. Sharpe, 1918:815, figs.
1269a, b, c, d, e, f.
Type Locality: Illinois.
Description of the Female (after Sharpe, 1597, 1903): A species of
the genus Cyprinotus. Shell from the side, nearly elliptical, elongate ;
dorsal margin evenly arched with the greatest height near the center.
The ventral margin is nearly straight, but with a slight sinuation near
the center. The anterior and posterior ends rounded, the posterior more
broadly. In view from above, according to Sharpe’s figures (1897:pl.
42, fig. 2; 1903:pl. 68, fig. 2), the left valve is slightly smaller than the
right; the anterior end is rather acutely pointed, the posterior more blunt.
However the text of Sharpe’s description of 1903 reads as follows:
“The right valve of shell is slightly smaller than the left, its anterior
margins armed with a row of about twenty-five tuberculiform teeth.
The margin of the left valve has a rather wide hyaline flange and a row
of scattered tubercles along the inner margin.” The size of individuals
range from 1.1 mm. to 1.4 mm. long, 0.80 mm. high and 0.51 mm. wide.
The swimming setae of the antennae reach but little beyond the
distal ends of the terminal claws. The claw-like setae of the outer
masticatory process of the maxilla are toothed. The furca is stout,
slightly bent, and about twice as long as the terminal claw. The sub-
terminal claw is about three-fourths of the length of the terminal one.
The dorsal seta has a length about equal to the length of the subterminal
claw and is removed from the base of the subterminal claw by a distance
less than the least width of the furcal ramus. The terminal seta is about
one-half as long as the dorsal seta.
Males: Unknown.
Remarks: The present writer has found it impossible to determine
exactly what Sharpe had when he described Cyprinotus pellucida (sic!)
in 1897. The writer believes that Sharpe may have founded his species
upon immature individuals since he does not show the ovaries in the
drawings of the shell even though he states that the shell is very trans-
parent. In almost every morphological detail, the descriptions given by
Sharpe (1897, 1903, 1918) for this species checks accurately with im-
mature individuals of Cyprinotus incongruens. It is, however, impossible
to reconcile the shell differences in valve overlap in C. incongruens and
C. pellucidus. In adult C. incongruens the left valve overlaps the right
and the same condition is usually found in the young with the exception
that in some young individuals the valves appear equal in size. Regard-
OSTRACODS OF ILLINOIS—HOFF 147
ing C. pellucidus, Sharpe (1903) states that the right valve is smaller than
the left. In his drawings, however, in 1897, 1903, and 1918, the right
valve is always shown as the larger. If the text of his 1903 description
is correct and the left valve is larger than the right, then possibly
C. pellucidus is a synonym of C. incongruens. On the other hand, if the
left valve is consistently smaller than the right (as shown in the drawing
by Weckel (1914, fig. 7)), then C. pellucidus must be retained as a valid
species.
The unsatisfactory and uncertain manner in which the genus
Cyprinotus was diagnosed in the first decade of the present century is
shown by Sharpe transferring his species pellucida from the genus
Cyprinotus to the genus Cypris in 1903. Part, at least, of this uncertainty
was the result of several writers about 1900 attempting to characterize
certain genera by the manner of propagation in the included species.
Since the genus Cyprinotus was thought to contain only species whose
individuals reproduced by syngamy, it was necessary to exclude the
species C. pellucidus because males were and still are unknown. Later,
this criterion was practically neglected and the genus Cyprinotus recon-
structed along entirely morphological lines. Because the manner of
reproduction varies in morphologically united groups of ostracods, it is
not possible to use the manner of reproduction as a generic criterion.
Ecology: Sharpe (1897) reports this species from a roadside ditch
and from a creek, as well as from an aquarium started with material
fotaea creek, Later (1903) he reported it from a trough fed by a
spring (Idaho).
Distribution: Sharpe (1897) described this species from material
taken in Adams, Mason, and Champaign Counties, Illinois. Later, he
(1918) gave the range of this species as Washington, Idaho, Illinois, and
Mexico. The present writer has not rediscovered this species in Illinois.
SUBFAMILY NOTODROMINAE
Distal podomere of the antenna long and slender; swimming setae
extend far beyond the terminal claws. Outer masticatory process of the
maxilla with six nearly equal, spine-like, toothed setae (fig. 113). Third
thoracic leg with three unequally long setae. Ductus ejaculatorius with
chitinous supporting rays not arranged in regular rows.
KEY TO GENERA OF THE SUBFAMILY NOTODROMINAE IN ILLINOIS
a. Antenna of six apparent podomeres; first thoracic leg without respiratory
plate; distal three setae of third thoracic leg unmodified ; terminal seta of the
fa camy am tate Clie el) are yystels crs avai meter ee ore Genus Notopromas Lilljeborg 1853
b. Antenna of five podomeres; first thoracic leg with a respiratory plate; setae
on distal end of third thoracic leg modified for grasping; terminal seta of
furca PIESEMt. 0... e sees e eee eect ee eee ec eee ee eenens Genus Cyprois Zenker 1854
148 ILLINOIS BIOLOGICAL MONOGRAPHS
Genus NOTODROMAS LIttyesore 1853
Shell short with the height at least two-thirds of the length; dorsal
margin forming an elevated arch; ventral surface flattened (fig. 112).
Eyes well separated. The antenna with the penultimate podomere divided
and so appearing to consist of six podomeres; the apparent distal podo-
meres long and slender, the swimming setae extending beyond the tips
of the terminal claws. The respiratory plate of the first thoracic leg is
lacking. The palps of the maxillae in the male are not similar; each is
formed of two podomeres. Ultimate podomere of third thoracic leg small
and with three almost equal setae. Furca with the terminal seta wanting ;
the dorsal seta very heavy and not far removed from the subterminal
claw (fig. 114). A genus with few species: one from Sumatra, one from
Ceylon, and one from the Holarctic region (Sars, 1928).
Notodromas monacha (O. F. Miller 1776) Lilljeborg 1853
(Pl. VIII, figs. 112-114)
Cypris monacha O. F. Miller 1776. O. F. Miller, 1776:199.
Notodromas monachus (O. F. Miller 1776) Lilljeborg 1853. Lilljeborg, 1853:95-102,
pl. 8, figs. 1-15; pl. 12, figs. 1, 2; pl. 25, fig. 16; Herrick, 18822252.
Notodromas monacha (O. F. Miller 1776) Lilljeborg 1853. Sharpe, 1908:417-419,
pl. 59, figs. 1-8; Shelford, 1913:144, fig. 94; Sharpe, 1918:808, figs. 1255a, b,
c, d, e.
Type Locality: Europe.
Description of the Female: A species of the genus Notodromas.
Shell with the greatest height about seven-tenths of the length; greatest
height slightly posterior to the middle of the elevated dorsal margin.
Posterior end more broadly rounded than the anterior; ventral margin
nearly straight and produced posteriorly into a point beyond the posterior
shell margin. From above, ovate with greatest width behind the middle
and equal to two-thirds of the length. Length 1.1 mm.
The ultimate podomere of the antenna equal in length to the pen-
ultimate; the swimming setae of the antenna reach the tips of the single
terminal claw. Furca curved, with the terminal claw greatly exceeding
in length one-half of the ventral margin of the furca.
Description of the Male: Male with shell (fig. 112) larger than
female; ventral margin bowed without a posterior tooth-like projection.
Length of shell 1.2 mm. Appendages as in the female. Prehensile palps
well developed and dissimilar; furca (fig. 114) more curved than in the
female.
Remarks: A detailed description of N. monacha is not needed here
since Sharpe in 1908 adequately described and figured this species from
material taken in northwestern Indiana.
OSTRACODS OF ILLINOIS—HOFF 149
Ecology: N. monacha has been reported by Sharpe (1908) as living
in “permanent bodies of pure fresh water which 1s also rich in aquatic
vegetation.” The single male individual of this species taken by the
writer was collected from the shore of a lake where there was an abun-
dance of aquatic plants. This species is rare as this single individual was
found in one of more than seventy-five collections made by Mr. Bertrand
A. Wright and by the writer at different times from the lakes in McHenry
and Lake Counties, northwest of Chicago, Illinois.
Distribution: N. monacha has been reported from Minnesota by
Herrick (1882) and from northern Indiana (near Chicago, Illinois) by
Sharpe (1908) and Shelford (1913). Dobbin (1941) reports it from
Alaska. The present writer’s collection was made on June 29, 1940, from
south of Waucanda, Lake County, Illinois. In general, this species is
widely distributed throughout the Holarctic region.
GeNus CYPROIS ZeEnKER 1854
Shell from the side, short and high, greatest height about two-thirds
of the length; ventral side of the shell not flattened. Eyes not widely
separated. Antennae of five podomeres; the penultimate podomere not
divided ; the ultimate podomere small with several end claws. The swim-
ming setae almost reach the tips of the end claws. Right and left pre-
hensile palps of male differing little. First thoracic leg with a well
developed respiratory plate. Ultimate podomere of the third leg small,
being partially enclosed by the penultimate podomere. Distally, the third
leg forms a seizing apparatus similar to that found in the members of the
subfamily Cyprinae s. str.; with only two conspicuous distal setae, the
third being reduced to a tooth-like structure. Furca with two claws and
two setae. A single species is found in Illinois.
Cyprois marginata (Strauss 1821) Zenker 1854
Cypris marginata Strauss 1821. Strauss, 1821:59, pl. 1, figs. 20-22.
Cyprois marginata (Strauss 1821) Zenker 1854. Sharpe, 1908:415-416, pl. 58, figs.
1-5; Shelford, 1913:177, 179, 185, fig. 129; Sharpe, 1918:809, figs. 1256a, b, c, d.
Type Locality: Europe.
Description of the Female (chiefly after Klie, 193Sa): An ostracod
of the genus Cyprois. From the side, shell high in the middle, greatest
height about seven-tenths of the length. Anterior margin evenly rounded;
the posterior margin flatly rounded; and the ventral margin slightly sinu-
ate. Seen from above, the right shell overlaps the left; the anterior is
more pointed than the posterior; and the greatest width which is about
150 ILLINOIS BIOLOGICAL MONOGRAPHS
one-half of the length lies in the middle of the shell. Shell measures
1.7 mm. in length.
The penultimate podomere of the antenna narrow, terminal claws
slender ; swimming setae extending to the tip of the claws. Furcal ramus
little curved; dorsal seta modified claw-like and subequal to the terminal
claw.
Description of the Male (after Sars, 1928): Shell of male smaller
than that of female. Shell similar to that of female except the posterior
margin is more rounded. Prehensile palps nearly equal in shape and
size. Furcal ramus much more curved in the male than in the female.
Length of shell of male about 1.5 mm.
Remarks: Representatives of this species have not been collected
by the present writer in Illinois. As a result, it is thought advisable to
give only a brief synopsis of the specific description as complete descrip-
tions may be found in both European and American works on ostracods
(vid. Sharpe, 1908).
Ecology: Both Sharpe (1908) and Shelford (1913) report this species
from vernal ponds.
Distribution: Cyprois marginata is found throughout most of the
Holarctic region except Asia. Sharpe (1908) and Shelford (1913) found
this species in the region of Jackson Park, Chicago, Illinois. Furtos
(1933) found this species in Ohio.
SUBFAMILY CYPRIDOPSINAE
Shell from the side, usually high and short (figs. 115, 118); from
above, either tumid or compressed. Length of shell not over 1.0 mm.
Antenna of five podomeres with swimming setae well developed or
reduced. Outer masticatory process with two spine-like setae either
toothed or smooth. Distal end of third thoracic leg modified for grasping
(fig. 120). Furca reduced to a base ending distally in a long seta or
“flagellum” (fig. 117). Reproduction in many species entirely partheno-
genetic. The subfamily is cosmopolitan.
KEY TO GENERA OF THE SUBFAMILY CYPRIDOPSINAE IN ILLINOIS
a. Shell tumid, valves nearly equal; ultimate podomere of the maxillary palp
cylindrical longersthany widewraiee cece Genus Cypripopsis Brady 1867
b. Shell compressed, right valve higher than the left and extending dorsally
above the left; ultimate podomere of the maxillary palp distally wider than
Leste (ines LID) patie Gaeeete «sl caeee «ele rok oe tate ORR Genus Potamocypris Brady 1870
OSTRACODS OF ILLINOIS—HOFF 151
GeNus CYPRIDOPSIS Brapy 1867
Shell short, high, tumid (fig. 115). Valves differ little, neither
projects conspicuously above the other dorsally. Swimming setae of the
antenna well developed. Terminal podomere of the maxillary palp
cylindrical, not widened distally. The respiratory plate of the first
thoracic leg carries two or more setae. Furca greatly reduced, con-
sisting of a base tapering distally to form a long seta or “‘flagellum”’ with a
second shorter seta attached to the posterior margin close to the distal
end of the base (fig. 117). Members of this genus are found in nearly
all parts of the world. A single species, Cypridopsis vidua (O. F. Miller
1776), known from Illinois.
Cypridopsis vidua (O. F. Miller, 1776) Brady 1867
(Pl, VIII, figs. 115-117)
Cypris vidua O. F. Miller 1776. O. F. Miller, 1776:199.
Cypridopsis vidua (O. F. Miller 1776) Brady 1867. Sharpe, 1897:469-470; Kofoid,
1908:258; Shelford, 1913:152, figs. 8la, b; Sharpe, 1918:807, fig. 1253.
Cypridopsis vidua obesa Furtos 1933 (non Brady and Robertson 1869). Furtos,
1933:431.
Cypridopsis pustulosa Furtos 1933. Furtos, 1933:431-432, pl. 6, figs. 5-9.
Type Locality: Europe.
Description of the Female: A species of the genus Cypridopsis. Shell
(fig. 115) from the side: ovoid in shape; the greatest height just pos-
terior to the center and about two-thirds of the length. Dorsal margin
broadly arched, usually with a definite angulation at the highest point.
Ventral margin slightly sinuated in most shells; anterior and posterior
margins rounded, the anterior slightly more narrowly rounded than the
posterior. The ventral surface is flattened. Seen from above: shell
tumid; the greatest width is slightly posterior to the middle and little ex-
ceeds the greatest height. The anterior margin of the right valve
(fig. 116) with fifteen to twenty tubercles which are inconspicuous in
some individuals. The surface of the shell is marked by minute impres-
sions. The surface is hairy. The shell is yellowish white to light green
in color and usually is ornamented by four color bands which extend
from the dorsal margin down the side of each valve. These bands vary
in color from light green to dark green, to black in some individuals.
There are usually four bands which are placed as follows: one along
the posterior margin of the shell, one near the anterior margin, one im-
mediately behind the eye, and one between the last mentioned and the
posterior band. These blotches or bands vary considerably in intensity
152 ILLINOIS BIOLOGICAL MONOGRAPHS
and indeed may be too weak to be detected by reflected light. Such bands
may be demonstrated on isolated valves by the use of transmitted light.
The swimming setae of the antennae extend beyond the ends of the
terminal claws. The respiratory plate of the first thoracic leg bears
five setae. The terminal seta or “flagellum” of the furca (fig. 117) about
equals twice the length of the base. Average length of the shell is about
0.70 mm.
Male: Unknown. The report of males from middle Europe by Spandl
(1925) is doubted by European workers (Klie, 1938a).
Remarks: Cypridopsis vidua is variable in shape, size, and color. The
greatest variation is in the color bands, some individuals having dark con-
spicuous bands, others inconspicuous bands. The apparent absence of
color bands has led many investigators to assign individuals to the
species C. obesa Brady and Robertson 1869. Furtos (1933), for example,
assigns certain individuals to C. vidua obesa Brady and Robertson 1869 in
spite of the fact that she found no anatomical differences between the
two forms, vidua and obesa, as they occur in Ohio. Since there are
differences in shell shape and the number of setae on the respiratory
plate of the first leg in vidua and obesa and these differences have been
recognized by Sars (1928) and Klie (1938a), it is apparent that Furtos
has erred in assigning the Ohio specimens with the anatomical character-
istics of vidua to the group obesa. It is very doubtful if Cypridopsis obesa
occurs in North America, as all illustrations of American individuals as-
signed to obesa are without doubt indistinctly banded individuals of
vidua. The writer has found a great variation in color in single popula-
tion samples ; and, indeed, many shells, which appear to be without bands,
are seen to have bands when cleared valves are examined by transmitted
light.
The variability of the shell is demonstrated by the tubercles along
the anterior margin of the right valve. This variation in size and number
of tubercles has led to some confusion which has culminated in the
creation by Furtos (1933) of a new species, Cypridopsis pustulosa, to
include individuals which are unbanded and which have tubercles along
the anterior margin of the right valve. Although most authors do not
mention these tubercles, they are known to occur in Cypridopsis vidua,
as Klie (1938a) states: “Der V. R. [Vorderrand] der r. Sch. [rechte
Schale] weist an der Innenseite eine aus etwa 20 winzigen Hockerchen
bestehende Kornelung auf.” These tubercles are often inconspicuous but
may nearly always be detected even when very minute by an examination
under high magnification of isolated right valves which have been: deeply
stained in acid fuchsin and cleared. There appears to be no correlation
between the intensity of the color bands and the prominence of the tu-
OSTRACODS OF ILLINOIS—HOFF 153
bercles. In fact, many shells showing deeply colored blotches distinctive
of vidua also show pronounced tubercles (which Furtos gives as the chief
characteristic of her species pustulosa) along the anterior margin of the
right valve.
The cause of the variability in color is unknown. It is doubtful if it
is the result of the development of populations differing in color. The
present writer has noticed that individuals taken in late summer from
masses of algae and aquatic vegetation are usually more darkly colored
than are specimens taken earlier in the season before the green plants
replace the dead vegetation left from the previous year. It is entirely
possible that either through the action of additional sunlight or by the
ingestion of more green plant material, the pigment may become more
highly developed. Such an hypothesis would necessarily require verifica-
tion experimentally.
‘ Ecology: Cypridopsis vidua is the most common of all the ostracods
in Hlinois. It was taken by the present writer in 505 of the 713 collec-
tions made in IIlinois. Not only is it found everywhere, but there are
few ostracods which are found in such great numbers of individuals in
single collections. It is especially abundant in permanent still waters
although it will tolerate considerable current when aquatic vegetation
is present as a substratum. It is found only to a limited extent in April
and May, and for this reason is not often taken from early vernal ponds.
Cypridopsis vidua is present in most collections made in June and July
regardless of the habitat although they reach their greatest abundance
in the algae and aquatic vegetation of permanent lakes, river backwaters,
and vernal ponds which do not dry up until late in the serotinal season.
Distribution: This species is common throughout the Holarctic aoe
and has been reported from the Neotropical as well (Klie, 1926a).
every county in Illinois in which the writer made a reasonable ne
Cypridopsis vidua was present.
Genus POTAMOCYPRIS Brapy 1870
Shell compressed; the right valve projects much beyond the left
dorsally. Valves usually hairy (fig. 118). Swimming setae of the second
antenna usually well developed (fig. 118-S); extending to the tips of
the terminal claws or beyond. Terminal podomere of the maxillary palp
short, distally wider than long, and armed with short claw-like setae
(fig. 119). The respiratory plate of the first thoracic leg with not more
‘than two setae.
Only one species, P. smaragdina (Vavra 1891), known from Illinois.
154 ILLINOIS BIOLOGICAL MONOGRAPHS
Potamocypris smaragdina (Vavra 1891) Daday 1900
(Pl. VIII, figs. 118-124)
Cypridopsis smaragdina Vavra 1891. Vavra, 1891:80-81, fig. 26; Sharpe, 1897:470-
471, pl. 48, figs. 11-12.
Potamocypris smaragdina (Vavra 1891) Daday 1900. Sharpe, 1903:992, pl. 65, figs.
5-7; 1918:808, figs. 1254a, b, c.
Potamocypris smaragdina (Vavra 1891) var. compressa Furtos 1933, Furtos, 1933:
435-436, pl. 6, figs. 10-14; Dobbin, 1941:231-232, pl. 2, figs. 1-6.
Type Locality: Bohemia.
Description of the Female: A species belonging to the genus Potamo-
cypris. Shell (fig. 118) from the side with a high rounding dorsal margin,
giving the shell a three-sided appearance. The greatest height is little
more than one-half the length; greatest height behind the eye but anterior
to the middle of the dorsal margin. Posterior end pointed and narrower
than the anterior. The margins of the two ends merge into the dorsal
margin without any interruption. The ventral margin is slightly sinuated.
The right valve extends above the left dorsally; the left shell extends
beyond the right by its hyaline flange both. anteriorly and posteriorly.
This flange is confined posteriorly to the posterior-ventral corner and
intensifies the acutely pointed appearance; anteriorly it extends from a
little below the eye along the anterior margin of the shell and ends near
the anterior end of the ventral margin. Considerable variation is shown
in the extensiveness of the development of this flange. From above, the
shell appears elliptical, bluntly pointed posteriorly, more acutely pointed
anteriorly ; the greatest width is less than one-half the length and located
in front of or near the middle. Surface of shell hirsute; the hairs are
stout and almost spine-like, directed posteriorly parallel to each other.
They are appressed closely to the shell surface. The valve surfaces are
pitted. The color varies but is usually light green or yellowish-green
and commonly displays two dorsal lateral blotches of some shade of green.
Length and height of valves of several females from Illinois (mounted in
diaphane and measured to include the flanges) are as follows:
RIGHT LEFT
Length Height Length Height
0.64 mm. 0.39 mm. 0.66 mm. 0.38 mm.
0.62 0.36 0.64 0.35
0.63 0.37 0.66 0.38
0.56 0.36 0.58 0.36
The swimming setae of the antennae extend beyond the ends of the
terminal claws by one-third of their own length which is about equal
to the length of the claws. The base of the furca narrows rapidly to
form the “flagellum.”
Description of the Male: The shell of the male differs somewhat
OSTRACODS OF ILLINOIS—HOFF 155
from the female in size and shape. On the whole, the (fig. 121) shell is
much more elongate, the height little more than one-half of the length;
the peak of the dorsal margin more attenuated than in the female. The
anterior and posterior slopes of the dorsal margin are also more flattened.
The ventral margin is conspicuously sinuated; the hyaline margin of the
anterior end is well developed. The coloration, sculpturing, and hirsute-
ness of the shell similar to the female. The testes extend in the form of a
whorl to the anterior one-half of the shell (fig. 121-A). The soft parts
are like those of the female.
Measurements of the shell halves of several mature males (mounted
in diaphane; measurements include the hyaline border or flange
(fig. 121-F)) are as follows:
RIGHT LEFT
Length Height Length Height
O:52 mm... 0:28 mm: 0.58 mm. 0.32 mm.
0.52 0.28 0.55 0.29
0.56 0.32 0.61 0.33
The right prehensile palp (fig. 122b) has a long cylindrical propodus
with two stout setae near the distal end of the anterior margin; the
dactylus is narrow and gently curved. The left prehensile palp (fig. 122a)
is larger than the right, the propodus is stout and has two small lateral
setae near the distal end of the anterior margin. The dactylus is stout,
falciform, and is acutely pointed with a small protuberance near the point.
The ductus ejaculatorius (fig. 123) is elongated with thirteen to fifteen
rows of chitinous spines. The penis (fig. 124) has a wide base and a
single lateral lobe. The lateral lobe is distally bilobed, stout, and extends
beyond the blunt end of the base.
Males were present in six of fifty collections selected at random. They
appear to be equal in number ‘to the females in the collections in which
they occur. There seems to be no correlation between the presence of
males and the season or locality in which they occur.
Remarks: Potamocypris smaragdina is extremely variable in size,
shape, and color of shell. This variability, along with the mistakes in
the original description as given by Vavra (1891), has led to some mis-
conception regarding this species. In assigning Illinois material to P.
smaragdina, Sharpe (1897) remarks that the eye in Illinois material is
below and anterior to the highest point of the shell in contrast to the
condition in the type material of which Vavra (1891) wrote: “Die
Schale ist fast dreiseitig, im ersten Drittel, ber dem durch die Schale
durchschimmernden Auge am hochsten.” If a straightedge is laid along
the dorsal margin parallel to the ventral margin of the shell in Vavra’s
drawing (1891:81, fig. 26 (1)), it will be found that the highest point
156 ILLINOIS BIOLOGICAL MONOGRAPHS
of the shell is distinctly posterior to the eye much as it is in Illinois
specimens.
Furtos (1933) seems also to have been led astray by Vavra’s incomplete
and erroneous description of the type material. She bases the separation
of her variety compressa from the type of Vavra on two differences:
(1) the Ohio form is longer, lower, and narrower than the European,
and (2) the swimming setae of the antennae in the Ohio form extends
beyond the terminal claws by the length of the claws rather than “beyond
the terminal claws by only one-third the length of the claws” (Furtos,
1933) as in the European form. Both of these differences may be ob-
literated when Vavra’s description is properly understood. In the first
place, the height, 0.48 mm., given by Vavra (1891) is plainly an error. If
the shell figured (Vavra, 1891:fig. 26 (1)) is measured and the height
computed from the height-length ratio (assuming the length to be 0.68
mm.) the height will be about 0.38 mm. Thus the height is little more than
one-half the length. This is verified by Wagler (1937). The height of the
variety compressa as given by Furtos then coincides with this computed
height for P. smaragdina of Europe. The error in the height given in
Vavra’s work is apparently a typographical error. Such errors are very
common in Vavra’s work on the ostracods of Bohemia and several others
occur in Vayra’s description of P. smaragdina. Regarding the difference
in length of the swimming setae of the antennae as given by Furtos,
there has been a misunderstanding in the reading of Vavra’s description.
From the nature of his sentence structure, it is impossible to tell whether
he intended to say that the swimming setae extend beyond the end claws
of the antenna by one-third of the length of the setae or one-third of
the length of claws, for he (1891) writes: “Von den ubrigen Arten
[Cypridopsis villosa| unterscheidet sie sich hauptsachlich durch die Bil-
dung des zweiten Antennenpaares, dessen am Ende des dritten Gliedes
inserirte Schwimmborsten sehr lang sind, so dass sie das Ende der
Klauen um ein drittel ihrer Lange tiberragen.” Furtos (1933) took this
to mean that the setae extend beyond the claws by one-third of the length
of the claws. However, that Vavra meant that the setae extend beyond
the end claws by one-third of the length of the setae is supported by
Wagler (1937) who writes: “Schwimmbo. [Schwimmborsten] der Ant.
[Antenne] iiberragen die Endkl. |[Endklaue] um 1% ihrer eigenen Lg.
[Lange].” Thus there remains no difference between the var. compressa
of Furtos and the typical European form except a slightly smaller width
in the former. This difference can probably be assigned to individual
variation.
Ecology: Potamocypris smaragdina is a common species especially
of permanent waters. Only twenty of the one hundred and eighteen
collections made by the writer containing this species were from tempo-
OSTRACODS OF ILLINOIS—HOFF 157
rary still and running waters, the others from permanent waters, about
one-half from lakes and one-half from streams. The reason for not
finding this species in temporary waters may be its seasonal appearance
for it seldom becomes abundant before late May when many of the
temporary waters have become dry. This species usually reproduces par-
thenogenetically but a number of males do occur in many collections.
Distribution: This species is found in North America and in Bo-
hemia and Switzerland in Europe. The writer has taken it from all
parts of the state of Illinois although it is much more abundant in the
northern two-thirds than in the southern one-third of the state.
FAMILY DARWINULIDAE
Surface of shell smooth; hinge without teeth. Antennule composed
of six podomeres, with strong spine-like setae. Antenna with a base of
two podomeres and an endopodite of three podomeres, also a vestigial
exopodite armed with two setae. Swimming setae lacking. Mandible with
a short palp of three podomeres; of which the first is wide and has a
row of long feathered setae. The respiratory plate of the mandible is
small and is armed with short setae. The masticatory processes of the
maxilla are short and heavy; the palp has two podomeres, the basal one
wide, the distal one small and relatively narrow. The respiratory plate
of the maxilla well developed, very large, with numerous large feathered
setae. the first thoracic leg with a strong masticatory structure; a leg-like
palp of three podomeres, and a circular respiratory plate with numerous
setae. The second and third thoracic legs are similar, each composed of
five podomeres and adapted for crawling. The furca is completely lacking,
the body ending posteriorly in a short, unpaired cone-like projection
(fig. 126). The ovaries do not originate in the cavity between the shell
plates ; the female carries the eggs in the posterior dorsal part of the shell
cavity during their development. A single genus is known.
GENUS DARWINULA Brapy anp NorMAn 1889
With characteristics of the family Darwinulidae.
Of the few species known, only one, Darwinula stevensoni, has been
reported from North America.
Darwinula stevensoni (Brady and Robertson 1870)
Brady and Norman 1889
(Pl. IX, figs, 125, 126)
Argilloecia (?) aurea Brady and Robertson 1870. Brady and Robertson, 1870: 16,
pl. 8, figs. 4-5.
158 ILLINOIS BIOLOGICAL MONOGRAPHS
Polycheles stevensoni Brady and Robertson 1870. Brady and Robertson, 1870:25-26,
pl. 7, figs. 1-7; pl. 10, figs. 4-14.
Darwinula stevensoni (Brady and Robertson 1870) Brady and Norman 1889. Brady
and Norman, 1889:122-123, pl. 10, figs. 7-13; pl. 13, figs. 1-9; pl. 23, fig. 5.
Darwinula improvisa Turner 1895. Turner, 1895:336-337, pl. 81, figs. 1-3, 13.
Darwinula stevensoni (Brady and Robertson 1870) Brady and Norman 1889.
Sharpe, 1918:807, fig. 1252.
Type Locality: British Isles.
Description of Female: An ostracod of the genus Darwinula. From
the side, the shell (fig. 125) very narrowly wedge-shaped with the
broader end posterior. The greatest height equal to about two-fifths of
the length and highest near the middle of the posterior one-half of the
shell. The dorsal margin is very flatly arched; the ventral margin is
straight. Viewed from above, the shell appears elongate; the greatest
width lies at the posterior one-third and is greater than one-third of the
length; posterior end rounded, anterior end pointed. The right shell
extends beyond the margins of the left both anteriorly and posteriorly.
Each of the nine muscle scars are wedge-shaped and together form a
rosette in the posterior part of the anterior one-half of the shell. The
shell measures about 0.70 mm. in length. The distal podomere of the
mandibular palp is several times longer than wide.
Males: The present writer has seen no males of this species. There
are no available descriptions of males; the extent of reports in the
literature regarding the nature of the male is a single drawing of the penis
by Brady and Robertson (1870:pl. 10, fig. 13).
Remarks: G. W. Miller (1912) in “Das Tierreich”’ lists this species
under the designation D. aurea (Brady and Robertson 1870). Brady
and Robertson described this species twice in the same publication, first
under the specific designation aurea (1870) and then under stevensoni
(1870). Since there is no statement in the International Rules of Nomen-
clature which would require the recognition of the first (according to
the pagination) of two names given in a publication, the name stevensont
rather than aurea should be retained for this species because: (1) in
stevensoni the description is based on several individuals while the
description of aurea is based on a single individual; (2) the description
and figures of stevensoni are more complete than those for aurea; (3) the
designation stevensoni was preferred by Brady in the work by Brady and
Norman (1889) and aurea is given as a synonym; (4) stevensoni is a
long established name and is used by most writers.
Ecology: D. stevensoni appears to be an inhabitant chiefly of large
lakes. Turner (1895) reported it under the name D. improvisa from a
sandy bottom reservoir about three miles in circumference. The present
writer secured a single individual in material taken from the sandy bottom
OSTRACODS OF ILLINOIS—HOFF 159
of a large lake of glacial origin. That it is not always associated with
a sandy bottom is shown by Sars (1928) who found it on a muddy bot-
tom. This species usually reproduces parthenogenetically.
Distribution: D. stevensoni is nearly Holarctic in distribution, having
been reported from Europe and North America. In North America, it
was reported by Turner (1895) from Atlanta, Georgia. The present
writer found a single female in a collection made by Bertrand A. Wright
on August 8, 1940 from Hastings Lake near Antioch, Lake County,
Illinois.
FAMILY CYTHERIDAE
Shell variable in shape and sculpturing; seldom smooth, usually with
reticulations ; often with spines, furrows, or tubercles (fig. 127). Valves
nearly equal; often tooth-like projections along the hinge (fig. 137-AT,
PT). The antennules consist of a base of two podomeres and an
endopodite of three or four podomeres. The setae of the antennules are
short and stout, often claw-like. The exopodite or the flagellum” (fig.
131-F) of the antenna is represented by a long hollow seta forming a duct
carrying the secretion from a gland which is thought to furnish adhesive
material used by the animal in crawling over smooth surfaces. The
endopodite of the antenna is composed of three podomeres; the long
penultimate one may be divided. Swimming setae lacking. Three pairs
of thoracic legs similar and all adapted for crawling. Furca always
greatly reduced (fig. 138). In the male, the penis is always present and
well developed (figs. 134, 141); the ductus ejaculatorius is absent; and
a male accessory sense organ consisting of numerous setae on a short
base (fig. 135) is located between and somewhat medially to the bases of
the first and second pairs of thoracic legs. The gonads do not lie between
the plates of the valves but are in the body lateral to the intestine. In
some species, the eggs are retained in the shell cavity during development.
The family includes over thirty genera belonging to several sub-
families, most of which are marine. Two subfamilies, Limnocytherinae
and Entocytherinae, are known from the fresh-waters of North America.
KEY TO SUBFAMILIES OF THE CYTHERIDAE IN ILLINOIS
a. Free margins of valves flattened, with many long pore-canals (fig. 128-P) ;
shell usually subrectangular, often with protuberances or furrows (fig. 127);
the respiratory plate of the mandible well developed; the furca usually with
EWONSHOPESSELAG + (11o® 132) ici piston. a cate octowains ide ess Subfamily LimNnocyTHERINAE
b. Free margins of the valves without conspicuous pore-canals; shell usually
reniform or subelliptical and without furrows or protuberances; respiratory
plate of mandible usually reduced to two or three setae; the furca extremely
MC IHENLARV A ret Meer relteciclabe thd ciate: Srersreiete ecard piohe ere Subfamily ENntTocyTHERINAE
160 ILLINOIS BIOLOGICAL MONOGRAPHS
SUBFAMILY LIMNOCYTHERINAE
Shell weakly calcified. Margin of each valve with many pore-canals
(fig. 128-P). Eyes fused. Both antennules and antennae foot-like and
adapted for creeping. Exopodite (flagellum) (fig. 131-F) of the antenna
well developed in both sexes. Palp of the mandible of three podomeres
and with a well developed respiratory plate. Furca small, usually with
two short spine-like setae (fig. 138). The members of this subfamily are
entirely fresh-water in habitat. A single genus, Limnocythere, is known
from Illinois.
Genus LIMNOCYTHERE Brapy 1867°
Shell thin, usually with either protuberances or furrows (fig. 127-F,
P) or both; the free margin edge where the valves meet is extremely
wide with long, slender, often branching pore-canals (fig. 127-M).
Endopodite of the antennules consist of three podomeres, of which the
distal one is four times longer than wide and is armed with four setae of
which two are fused at their bases (fig. 130-F). Antenna with three
terminal claws; the exopodite (flagellum) is divided into basal and
distal portions by an articulation (fig. 131-A). Respiratory plate of the
mandible with five long apical and two short lateral setae. The palp of
the maxilla has a distinct distal podomere with one of the distal setae
claw-like. The thoracic legs are similar and each has two setae on the
anterior margin of the proximal podomere (fig. 139). Furca cone-shaped
with one terminal seta and one lateral seta (fig. 132). Three species
belonging to this genus are known from Illinois. .
In the literature there is some confusion regarding the proper spelling
of the name of this genus. Some writers as Sharpe (1897) and Sars
(1928) give the spelling as “Limnicythere.”” Most writers, on the
other hand, give the spelling as “Limnocythere.” The latter is correct.
It was used by Brady in a publication dated September, 1867. The
spelling wherein an “i” replaces the “o” results from certain writers
following a later publication by Brady (1868). The content of this later
publication was read before the Linnean Society of London in May, 1866.
Since reading a paper does not constitute publication, the more ortho-
graphically correct name, Limnocythere, stands as the valid designation
for this genus.
KEY TO SPECIES OF THE GENUS LIMNOCYTHERE IN ILLINOIS
la. Shell with conspicuous, well developed protuberances (fig. 127-P) ; anterior
margin of shell with tubercles (fig. 128-T); dorsal seta of furca arising
fronpra: papilla (dig LSZqD) 1/0 Se hie caer eded se Sree es oak L. verrucosa sp. nov.
b. Shell without well developed protuberances (fig. 140); anterior margin of
shell without tubercles; dorsal seta of furca arises directly from the base
without the intervention of a papilla (fig. 138-D))...::.0....2.2 o.s5 > se ee 2
OSTRACODS OF ILLINOIS—HOFF 161
2a. Shell with two dorsal-lateral furrows (fig. 140); surface sculpturing con-
spicuous; furca blunt, with one of the setae at the distal end (fig. 138)
«5 20 SOCIO i Oe eI Serer IO eas DICE ae ar L. reticulata Sharpe 1897
b. Shell with one dorsal-lateral furrow; surface sculpturing inconspicuous;
furca with base tapering to an acute point and both of the setae well re-
moved fron thevdistal ends. 3... 2 Shas oes bene ese L. illinoisensis Sharpe 1897
Limnocythere verrucosa sp. nov.
(Pl. IX, figs. 127-135)
Type Locality: West Loon Lake, Lake County, [linois.
Description of the Female: A species of the genus Limnocythere.
From the side: shell (fig. 127) subrectangular; height slightly more than
one-half the length; dorsal margin straight; ventral margin well sinuated
near the center; anterior margin evenly rounded with a very wide hyaline
border; posterior margin with an angulation near the center. Teeth of
the hinge weak. Four oval muscle scars with the longitudinal axis of each
scar parallel to the dorsal margin of the shell (fig. 127-S); the four
scars forming a row with the axis of the row at right angles to the axis
of each individual scar. The scars are subcentrally placed. The shell
bears laterally and dorsally in the anterior one-half two furrows (fig.
127-F). These are similar to the furrows in L. reticulata. Near the
furrows there are two large, rounded protuberances. One of these is
anterior and ventral to the anterior furrow; the other is posterior and
slightly vental to the posterior furrow. A third large protuberance is
located very near the ventral margin of each valve just posterior of the
deepest portion of the sinuation. The flattened, hyaline border (fig. 128)
of the shell contains numerous pore-canals near the outer ends of which
originate large setae. Between these setae the outer margin is plumose, the
hairs being closely placed and delicate. The anterior margin also has
eight to twelve small tubercles along its edge. The entire shell including
the hyaline borders is sculptured with small raised areas giving the shell
a reticulated appearance. From above, the shell (fig. 129) appears
moderately inflated as a result of the protuberances. The width is nearly
equal to the height, being but slightly more than one-half of the length.
The length and height of several right valves are as follows (mounted
in diaphane; measurement includes the hyaline border):
Length Height
0.55 mm. 0.30 mm. (holotype)
0.56 0.30
0.54 0.30
0.60 0.30
The antennules are stout; the length of the ultimate podomere is
five and one-half to six times the width. The two subdistal claws are
162 ILLINOIS BIOLOGICAL MONOGRAPHS
relatively short, subequal or equal to the ultimate podomere, and the tips
are on a level with the point of fusion of the two terminal setae. The
two terminal setae (fig. 130-F) are fused basally for a distance equal to
the length of the terminal podomere of the appendage. Of the unfused
ends of these two setae, the more slender one has a free portion which
is three times the length of the unfused portion of the stouter of the
pair. The “flagellum” (fig. 131-F) of the antenna reaches somewhat past
the center of the longest terminal claw. The terminal claws of the
thoracic legs are relatively short in comparison to those of most Limnocy-
there; the claw of the first leg is equal to the sum of the last two
podomeres of the appendage; the claw of the second leg is about one and
one-third times the sum of the lengths of the last two podomeres; and
the claw of the third thoracic leg has a length little more than the sum
of the distal three podomeres.
The furca (fig. 132) is peculiar in having a trilobed base; the middle
lobe is conical with a small needle-like seta on the blunt apex; the
posterior lobe (fig. 132-P) is small, papilla-like, and bears a long seta
which reaches to the distal end of the terminal lobe.
Description of the Male: The shell (fig. 133) of the male differs from
that of the female in being slightly longer and not relatively as high and
by having the protuberances greatly reduced. The shell is prominently
inflated directly above the ventral sinuation. The length and height of the
right valves of two male shells are as follows (mounted in diaphane;
the margins included in the measurements) :
Length Height
0.59 mm. 0.28 mm.
0.62 0.27
In the male, the sculpturing of the shell and the nature of the
margins are similar to those of the female. The appendages also differ
little from those of the female. The ultimate podomere of the antennule
is slightly more slender, and the “flagellum” of the antenna reaches nearly
to the tips of the end claws. The terminal claw of the third leg is equal
at least to seven-eighths of the length of the rest of the leg.
The base of the penis (fig. 134) has an irregularly curved anterior
margin. There are several appendages. One is L-shaped and is directed
posteriorly; a second large appendage passes along the base of the penis
and is directed anteriorly along the outside. It extends slightly beyond
the base anteriorly. Other smaller appendages and chitinous supporting
rods are present. The furca is very different from that of the female but
such differences are not unusual in species of this genus. The furca is
a tapering cone, very long and bearing two setae, one near the base and
another near the sharply pointed tip. The furca looks much like that of
L, illinoisensis Sharpe 1897 (Sharpe, 1897:pl. 39, fig. 12).
OSTRACODS OF ILLINOIS—HOFF 163
Remarks: Limnocythere verrucosa sp. nov. is markedly different
from other Illinois species of Limnocythere. The most readily available
criterion for recognition is the peculiar inflated condition of the shell
caused by the bulging protuberances. The furca of the female differs
from all other species of Limnocythere by having the posterior seta
elevated on a papilla.
Ecology: This species has been taken only from permanent lakes in
which there is an abundance of aquatic vegetation or alga.
Distribution: L. verrucosa was collected for the writer by Bertrand
A. Wright from West Loon Lake, Lake County, Illinois, on August 7,
1940. No other records are known.
The holotype (female) and allotype (male) of this species are
deposited in the U. S. National Museum (Cat. Nos. 81085 and 81086).
Paratypes of both sexes are in the collections of Dr. H. J. Van Cleave
and the writer.
Limnocythere reticulata Sharpe 1897
(Pl. IX, fig. 136-141)
Limnicythere reticulata Sharpe 1897. Sharpe, 1897:423-425, pl. 39, figs. 1-7; 1918:
806, figs. 1250a, b, c.
non Limnocythere reticulata Procter 1933. Procter, 1933:231, figs. 39a-d.
Type Locality: Urbana, Illinois.
Description of the Female: An ostracod of the genus Limnocythere.
From the side, shell (fig. 136) appears subrectangular; dorsal margin
straight; ventral margin with a sinuation; anterior and posterior margins
evenly rounded. The height is but little more than one-half of the length.
From above, the shell is elliptical with the sides slightly flattened and the
anterior end narrowly and acutely pointed. The greatest width is little
more than one-third of the length and lies posterior to the middle of the
shell. Each valve has two lateral furrows in the vicinity of the eye. The
surface is sculptured with a network of polygonal reticulations which
cover the surface except in the region of the eye. The four muscle scars
are arranged in a transverse row; each scar is elliptical in shape and lies
with its long axis parallel to the longitudinal axis of the other scars and
to the dorsal margin of the shell. The length of the shell is 0.65 to 0.70
mm. Length and height of right valves of several female shells from
Illinois are given as follows (mounted in diaphane and measured to
include the hyaline border) :
Length Hetghi
0.66 mm. 0.36 mm.
0.68 0.38
0.63 0.32
0.70 0.36
164 ILLINOIS BIOLOGICAL MONOGRAPHS
The antennules have a narrow ultimate podomere about seven times
as long as wide and are armed distally with four setae, two of which have
their bases fused. Of these two, one has the free portion about twice as
long as the free portion of the other. The antenna has three terminal
spines, the two longer ones are equal and have a length equivalent to
four times the length of the ultimate podomere. The third claw measures
about seven-eighths the length of the longer ones. The terminal claw of
the first thoracic leg is a little longer than the sum of the lengths of the
last two podomeres; terminal claw of the third leg very long, equal to the
sum of the last three and one-half podomeres. The furca (fig. 138) is
described by Sharpe (1897) as follows: “Rudimentary caudal rami
cylindrical, thick, blunt, about three times as long as wide, with a small
seta near base, not over two thirds as long as the width of the ramus,
and a stouter one near the tip of the ramus, twice as long as the preceding
one.”
Description of the Male: The shell (fig. 140) of the male differs con-
siderably from the female by being longer, relatively less high, and with
the posterior end more narrowly rounded and obtusely pointed. Measure-
ments of the right valves (borders included) of the shells of several
males from Illinois are as follows (mounted in diaphane) :
Length Height
0.74 mm. 0.34 mm.
0.76 0.38
0.78 0.40
0.72 0.36
The appendages are similar to those of the female except that the terminal
setae of the third leg (fig. 139) is much longer, the length being equal
at least to the length of the rest of the leg. The penis (fig. 141) is large;
the anterior margin is irregularly rounded; the base ends bluntly in a
point. Several appendages are present of which the largest is falciform
and extends posteriorly beyond the base.
Remarks: This species is readily distinguishable from other Illinois
species of Limnocythere by its reticulated shell surface and its lack of
protuberances. The blunt, short furca with the terminal seta near the
rounded distal end is an important diagnostic characteristic.
The record of this species by Procter (1933) from Lake Wood on
Mount Desert Island, Maine, appears to be based on an erroneous
specific determination. The shell pictured (Procter, 1933:figs. 39a, b)
is certainly not the reticulata of Sharpe since it is too elongate and the
dorsal margin is not straight. Likewise the illustration of the penis (his
fig. 39d) lacks the prominent appendage characteristic of the penis of
L. reticulata Sharpe.
OSTRACODS OF ILLINOIS—HOFF 165
Ecology: Limnocythere reticulata is a species from running waters
although it may be found on occasion in temporary pools. It is seldom
found in permanent lakes. It tolerates all conditions of current in streams
since it does not swim but creeps along the bottom or over the vegetation.
In the writer’s seventy collections of this species, all were taken in May
and June except one in July and one in August.
Distribution: Limnocythere reticulata is known only from Illinois.
Sharpe (1897) collected the type material from a pond near Urbana,
Champaign County, Illinois. The present writer has taken this species
from twenty-five counties scattered chiefly over the central and southern
parts of the state.
Limnocythere illinoisensis Sharpe 1897
Limnicythere illinoisensis Sharpe 1897. Sharpe, 1897:425-428, pl. 39, figs. 8-13; pl.
40, figs. 1-6; Kofoid, 1908:258; Sharpe, 1918:807, figs. 125la, b, c, d, e.
Type Locality: Havana, Illinois.
Description of the Female (after Sharpe, 1897): A species of the
genus Limnocythere. From the side, subelliptical with dorsal margin
straight, both ends evenly rounded, and the ventral margin with a deep
sinuation at the anterior one-third just below the muscle scars. The
greatest height of the shell is less than one-half of the length; the
posterior part of the shell has a greater height than the anterior part.
From above, the shell is pointed anteriorly; convex posteriorly; the
sides are nearly parallel and straight. There is a single lateral furrow ;
the shell reticulations are faint. The dimensions of the shell as given by
Sharpe are: length, 0.88 mm.; height, 0.40 mm.; width, 0.29 mm.
The terminal podomere of the antennule is four times as long as wide.
Terminal claw of second leg is nearly equal in length to the sum of the
lengths of the distal three podomeres of the appendage. “Rudimentary
caudal rami cylindrical, six to seven times as long as wide, gradually
tapering to a seta-like extremity which is five sevenths as long as the
main part of the ramus. Two dorsal setae: one situated about the width
of the ramus from base and as long as the width of the ramus; the other
just anterior to the seta-like termination, and about the same length as the
first” (Sharpe, 1897).
Description of the Male (after Sharpe, 1897): The male is much like
the female except for details of some of the appendages. The ultimate
podomere of the antennule is five times as long as wide, the terminal
claw of the antenna has three or four strong teeth near the tip. The claw
of the second leg has two or three accessory teeth near the tip; the claw
of the third leg is very long, as long as the lengths of the podomeres of
the leg united. This claw has cross-striations on the distal one-half.
166 ILLINOIS BIOLOGICAL MONOGRAPHS
Sharpe gives no verbal description of the male copulatory organs and it is
impossible to describe them adequately from his figure (Sharpe, 1897:pl.
40, fig. 2).
Remarks: The present writer has not observed individuals of this
species in any of his collections.
Ecology: Sharpe’s specimens were from lakes connected with the
Illinois River. Here the bottom was sandy. His collection of type
material was in May. Kofoid (1908) found this species during the
months of March, August, and November.
Distribution: The only known records of this species are those of
Sharpe (1897) and Kofoid (1908) regarding material taken mostly from
the Illinois River and connected lakes near Havana, Illinois.
SUBFAMILY ENTOCYTHERINAE
The subfamily Entocytherinae is represented in Illinois by two species
of the genus Entocythere, FE. idlinoisensis Hoff 1942 and E. copiosa Hoff
1942. For descriptions of these two species, the reader is referred to the
writer’s recent review of the subfamily Entocytherinae (Hoff, 1942).
SUMMARY
(1) The ostracods of Illinois, and the entire United States as well,
have received relatively little attention. Sharpe (1897, 1903, 1908, 1910)
investigated the ostracod fauna of Illinois but his work is relatively
incomplete since he confined his collecting of material chiefly to Cham-
paign, Mason, and Cook Counties. He gives little comprehensive infor-
mation on the ecology of the group in any of his publications.
(2) During the course of this investigation, the present writer traveled
nearly five thousand miles in the spring and summer of 1940. Over
seven hundred collections of ostracods were made from sixty-six
counties of the state. At the time of making each collection, the available
ecological data were recorded for future analysis.
(3) The writer found that the ostracod species of Illinois may be
separated into four groups according to habitat: (a) temporary running
waters as vernal streams; (b) temporary still waters as vernal ponds;
(c) permanent still waters as large lakes and the backwaters of rivers;
and (d) permanent running waters. While many species are typically
found in one of these four habitats, others fall into more than one group.
(4) An attempt was made to analyze the field data to find what factors
control the habitat range and distribution of ostracod species. It was
found that distribution is not correlated with the type of bottom but that
there is a distinct relationship between the amount of current in a habitat
and the presence of certain species of ostracods. The hydrogen ion con-
centration apparently has some effect upon distribution by inhibiting
certain species from extending their range to the southern part of the
state where the waters are Often acid. Two species of Cypria are able to
tolerate acid conditions.
(5) Ostracods do not enter into immutable association either with
other species of ostracods or species of plants found in the habitat. In
studying lakes, it is found that the same species of ostracods may be
found in all parts of a lake regardless of the kind of vegetation.
(6) Reproduction is both parthenogenetic and syngamic in some
species of ostracods, in other species one or the other of the types of
reproduction may predominate in varying degree. A list is given show-
ing the kind of reproduction in Illinois species as indicated by the relative
abundance of males.
(7) A short summary is given of the distribution of species of
ostracods living in Illinois both in relation to world-wide and state range.
Seventeen species are reported for the first time from Illinois. One
family, Darwinulidae, represented by a single species is reported for the
first time from the state.
(8) A complete discussion is given of the external morphology of the
167
168 ILLINOIS BIOLOGICAL MONOGRAPHS
fresh-water ostracods as an aid to future study and specific determination.
A summary is given of the morphology of various physiological systems.
(9) A discussion is given of the larger categories in the classification
of the order Ostracoda with a comparison of the systems devised by
various authors.
(10) In the systematic portion of the thesis, descriptions are given
of the thirty-nine free-living ostracod species reported from Illinois. Of
these, eleven are reported as being new to the literature. Of these new
species, ten belong to the family Cypridae and one belongs to the family
Cytheridae.
(11) Keys are given as an aid in the determination to species of the
free-living ostracods known to occur in Illinois.
BIBLIOGRAPHY
The following bibliographical list contains all the known references to the ostracods
of Illinois and in addition most publications relative to the fresh-water Ostracoda
of North America. Literature concerned with ostracods exotic to North America
is usually cited only when reference is made thereto in the text.
Publications indicated by the asterisk (*) have not been reviewed by the writer.
All of these are early writings which have little taxonomic significance except as
the descriptions have been expanded and completed by more recent workers.
ALLEN, S. A.
1933. Parasites and commensals of North Carolina crayfishes. J. Elisha
Mitch. Sci. Soc., 49:119-121.
ALM, GUNNAR
1914. Beitrage zur Kenntnis der nordlichen und arktischen Ostracodenfauna.
Ark. Zool., 9(5) :1-20.
1916. Monographie der Schwedischen Susswasser-Ostracoden nebst systema-
tischen Besprechungen der Tribus Podocopa. Zool. Bidr. Uppsala,
4:1-248.
BERGOLD, ALFRED
1910. Beitrage zur Kenntnis des innern Baues der Susswasserostracoden.
Zool. Jb. Anat., 30:1-42.
BERNECKER, A.
1909. Zur Histologie der Respirationsorgane bei Crustaceen. Zool. Jb. Anat.,
27 : 583-630.
BLAKE, CHARLES H.
1931. Two freshwater ostracods from North America. Bull. Mus. Comp. Zool.
Harvard, 72:279-292.
Brapy, G. S.
*1864. On species of Ostracoda new to Britain. Ann. Mag. Nat. Hist., Ser. III,
13:59-64.
1867. A synopsis of the recent British Ostracoda. Intell, Observ., 12:110-130.
1868. A monograph of the recent British Ostracoda. Trans. Linn. Soc. Lon-
don, 26:353-495.
*1870. Notes on Entomostraca taken chiefly in the Northumberland and Dur-
ham District. Nat. Hist. Trans. Northumb., 3:361-373.
1885. Notes on Entomostraca collected by Mr. A. Haly in Ceylon. J. Linn.
Soc. London, 19:293-317.
Brapy, G. S., and Norman, A. M.
1889. Monograph of the marine and freshwater Ostracoda of the North
Atlantic and of North-western Europe. 1. Podocopa. Trans. R.
Dublin Soc., Ser. II, 4:61-270.
Brapy, G. S., and Rosertson, D.
1870. The Ostracoda and Foraminifera of tidal rivers. Ann. Mag. Nat. Hist.,
Ser. IV, 6:1-33.
BreuM, V.
1932. Vorlaufige Mitteilungen iiber die Susswasserfauna Neuseelands. Zool.
Anz., 99:79-81.
1939. Zur Entomostrakenfauna der stidlichen Halbkugel. Zool. Anz., 126:33-40.
BRUuES, CHARLES T.
1932. Further studies on the fauna of North American hot springs. Proc.
Amer. Ac. Sci. Boston, 67:185-303.
CHAMBERS, V. T.
1877. New Entomostraca from Colorado. Bull. U. S. Geol. Geog. Sur. Terr.,
3:151-155.
Craus, C.
1872. Beitrage zur Kenntniss der Ostracoden, I. Entwicklungsgeschichte von
Cypris. Schr. Ges. Naturw. Marburg, 9:151-166. (Also published
separately in 1868).
169
170 ILLINOIS BIOLOGICAL MONOGRAPHS
1892. Beitrage zur Kenntniss der Sitisswasser-Ostracoden, I. Arb. zool. Inst.
Wien, 10:147-216.
1895. Beitrage zur Kenntniss der Siisswasser-Ostracoden, II. Arb. zool. Inst.
Wien, 11:17-48.
CocKERELL, T. D. A.
1912.. The fauna of Boulder County, Colorado, II. Univ. Colorado Stud.,
9:41-52.
CREASER, EDWIN P.
1931. Some cohabitants of burrowing crawfish. Ecology, 12:243-244.
CUSHMAN, JOSEPH A.
1905. A new ostracod from Nantucket. Amer. Natural., 39:791-793.
1907. Ostracoda from southeastern Massachusetts. Amer. Natural., 41:35-39.
1908. Fresh-water crustacea from Labrador and Newfoundland. Proc. U. S.
Mus., 33:705-714.
Dapay, E. von
*1900. Ostracoda Hungariae. Budapest.
1905. Untersuchungen tiber die Siisswasser-Mikrofauna Paraguays. Zoologica
(Stuttgart), 44:1-374.
Dana, JAMEs D.
1852. United States Exploring Expedition during the years 1837-1842 under
the command of Ch. Wilkes. Vol. 13. Crustacea. Part 2. Cypridae.
Philadelphia.
Doxssin, CATHERINE N.
1941. Fresh-water Ostracoda from Washington and other western localities.
Univ. Wash. Pub. Biology, 4:174-246.
Dopps, GIDEON S.
1908. A list of the Entomostraca of Colorado. Univ. Colorado Stud., 5:243-250.
Eppy, SAMUEL
1934. A study of fresh-water plankton communities. Illinois Biol. Mono.,
12 (4) :1-93.
FASSBINDER, K,
1912. Beitrage zur Kenntnis der Siisswasserostracoden. Zool. Jb. Anat., 32:
533-576.
FIscHEr, S.__
*1851. Uber das Genus Cypris und dessen bei Petersburg vorkommende Arten.
Mem. savants sci. St. Petersbourg, 7:127-167.
1855. Beitrag zur Kenntniss der Ostracoden. Abh. der Akad. Munchen
Mathem.-Physikal. Cl., 7:637-666.
Forses, S. A.
1888. Studies of the food of fresh-water fishes. Bull. Illinois Lab. Nat. Hist.,
2:433-538.
1893. A preliminary report on the aquatic invertebrate fauna of the Yellow-
stone National Park, Wyoming, and of the Flathead Region of
Montana. Bull. U. S. Fish Comm. 1891, 11:207-258.
FowLer, Henry W.
1912. The Crustacea of New Jersey. Ann. Rep. New Jersey Mus., 1911:29-651.
Furtos, Norma C,
1933. The Ostracoda of Ohio. Ohio Biol. Sur., 5:411-524.
1935. Fresh-water Ostracoda from Massachusetts. J. Washington Ac. Sci.,
25:530-544.
1936a. Fresh-water Ostracoda from Florida and North Carolina. Amer. Mid.
Natural., 17:491-522.
1936b. On the ostracods from the Cenotes of Yucatan and vicinity. Carnegie
Inst. Washington, pub. no. 457:89-115.
Ga.LtsorF, Paut S.
1937. General methods of collecting, maintaining, and rearing marine inverte-
brates in the laboratory. Culture methods for invertebrate animals.
Comstock Publishing Co., Ithaca, N. Y. Pages 5-40.
OSTRACODS OF ILLINOIS—HOFF 171
HA.LpEMAN, S. S.
1841. (Descriptions of new Cypris species). Proc. Ac. Nat. Sci. Philad., 1:53.
1842a. (Descriptions of new Cypris species). Proc. Ac. Nat. Sci. Philad., 1:166.
1842b. (Description of a new Cypris species). Proc. Ac. Nat. Sci. Philad., 1:184.
Hawnstroom, B.
1924. Beitrag zur Kenntnis des zentralen Nervensystems der Ostracoden und
Copepoden. Zool. Anz., 61:31-38.
Herrick, C. L.
1879. Microscopic Entomostraca. Ann. Rep. Geol. Nat. Hist. Sur. Minnesota,
7:81-123.
1882. On Notodromas and Cambarus. Ann. Rep. Geol. Nat. Hist. Sur. Min-
nesota, 10:252-254.
1887. Contribution to the fauna of the Gulf of Mexico and the South. Mem.
Denison Sci. Assoc., 1(1):1-56.
HirscHMANN, N.
1912. Beitrag zur Kenntnis der Ostrakodenfauna des Finnischen Meerbusens.
Acta Soc. Fauna Flora Fennica, 36(2) :1-66.
Horr, C. CLAYTON
1942. The subfamily Entocytherinae, a new subfamily of fresh-water Cytherid
Ostracoda, with descriptions of two new species of the genus Ento-
cythere. Amer. Mid. Nat., 27:63-73.
JOHANSEN, FRITZ
1921. The larger freshwater crustacea from Canada and Alaska. Canad. Field-
Natural., 35:88-94.
JurrineE, Louts
*1820. Historie des Monocles, qui se trouvent aux environs de Genéve. Genéve.
KAUFMANN, A.
1900a. Cypriden und Darwinuliden der Schweiz. Rey. Suisse Zool., 8:209-423.
1900b. Zur Systematik der Cypriden. Mitt. naturf. Ges. Bern, 103-109.
Kierer, F., and Kure, W.
1927. Zur Kenntnis der Entomostraken von Brunnengewassern. Zool. Anz.,
71:5-14.
Kutz, W.
1925. Muschelkrebse als Baumhohlenbewohner. Arch. Hydrobiol., 15:509-511.
1926a. Ostracoda. Biologie der Tiere Deutschlands, 22: 1-56.
1926b. Uber eine neue Art der Ostracodengattung Candona. Zool. Anz.,
66: 302-306.
1930. Ostracoden aus dem paraguayischen Teile des Gran-Chaco. Arch.
Hydrobiol., 22:221-258.
193la. Campagne spéologique de C. Bolivar et R. Jeannel dans l’Amérique du
Nord (1928). 3. Crustacés Ostracodes. Arch. Zool. exp. gén.,
71:333-344.
1931b. Zwei neue Arten der Ostracoden-Gattung Candona aus unterirdischen
Gewassern im stidostlichen Europa. Zool. Anz., 96:161-168.
1934. Zwei neue subterrane Ostracoden der Gattung Candona. Zool. Anz.,
106: 193-199,
1935. Drei neue Hohlenostracoden aus der Umgebung von Laibach. Zool.
Anz., 111:189-198.
1936. Neue Candoninae aus dem Grundwasser von Belgien. Bull. Mus. Hist.
nat. Belg., 12(13) :1-13.
1938a. Ostracoda, Muschelkrebse. Die Tierwelt Deutschlands und der Angren-
zenden Meeresteile, etc., 34:i-iv, 1-230.
1938b. Ostracoden aus unterirdischen Gewassern in Siiditalien. Zool. Anz.,
123: 148-155.
1938c. Candona bilobata, ein neuen Muschelkrebs aus dem Grundwasser der
unteren Mainteles. Zool. Anz., 124:216-220.
1938d. Ostracoden aus dem Grundwasser der oberrheinischen Tiefebene. Arch.
Naturg., new series, 7:1-28.
V3 ILLINOIS BIOLOGICAL MONOGRAPHS
Ktiucu, A. B.
1927. The ecology, food-relations and culture of fresh-water Entomostraca.
Trans. R. Canad. Inst., 16:15-99,
Kocu, C. L.
*1837-1841. Deutschlands Crustaceen, Myriopoden und Archniden. Heft 10,
11, 12 (1837) ; Heft 21 (1838); Heft 36 (1841).
Kororp, C. A.
1908. Plankton studies. V. The plankton of the Illinois River, 1894-1899.
Part II. Constituent organisms and their seasonal distribution. Bull.
Illinois Lab. Nat. Hist., 8:1-361.
LILLJEBoRG (LILJEBORG), WILH.
1853. De Crustaceis ex ordinibus tribus: Cladocera, Ostracoda et Copepoda,
in Scania occurrentibus. Lund. i-xv, 1-223.
MarsHALL, W. S.
1903. Entocythere cambaria nov. gen. et nov. spec., a parasitic ostracod. Trans.
Wisconsin Ac. Sci., 14:117-144.
MUtter, G. W.
1900. Deutschlands Stisswasser-Ostracoden. Zoologica (Stuttgart), 30:1-112.
1912. Ostracoda. Das Tierreich, 31:i-xxxiii, 1-434. (Complete consideration
of all literature prior to Dec. 31, 1908).
1927. Ostracoda. Kukenthal-Krumbach Handbuch der Zoologie, 3(1) :399-434.
MUtter, O. F.
*1776. Zool. Danicae Prodromus. Havniae.
*1785. Entomostraca seu Insecta testacea, quae in aquis Daniae et Norvegiae
reperit, descripsit et iconibus illustravit. Lipsiae et Hawniae.
MUtLEr-CaLk, K.
1913. Uber die Entwicklung von Cypris icongruens. Zool. Jb. Anat.,
36:113-170.
NEEDHAM, JAMES G., and Lioyp, J. T.
1930. The life of inland waters. Thomas, Springfield, Illinois. 1-438.
NEEDHAM, P. R.
1938. Trout streams. Comstock, Ithaca. i-x, 1-233.
Norvevist, O.
1885. Beitrag zur Kenntniss der inneren mannlichen Geschlechtsorgane der
Cypriden. Acta Soc. Sci. Fenn., 15:1-41.
Nowrkxorr, M.
1908. Uber den Bau des Medianauges der Ostracoden. Z. wiss. Zool., 91:81-92.
PEARSE, A. S.
1910. A preliminary list of the crustacea of Michigan. Rep. Michigan Ac. Sci.,
12:68-76.
1914. Report on the crustacea collected by the Walker-Newcomb Expedition
in Northeastern Nevada in 1912. Occ. Pap. Mus. Michigan, 3:1-4.
Procter, WILLIAM
1933. Biological survey of the Mount Desert Region. Pt. V. Marine fauna.
Wistar Institute of Anatomy and Biology, Philadelphia. 1-402.
Ramponr, K. A.
*1808. Uber die Gattung Cypris Mull. und drei zu derselben gehorige neue
Arten. Mag. Ges. Fr. Berlin, 2:83-93.
Rawson, Donatp S.
1928. Preliminary studies of the bottom fauna of Lake Simcoe, Ontario. Univ.
Toronto Stud. Biol., 31:75-102.
1930. The bottom fauna of Lake Simcoe and its role in the ecology of the
lake. Univ. Toronto Stud. Biol., 34:1-183.
OSTRACODS OF ILLINOIS—HOFF 173
Sars, G. O.
1890. Oversigt af Norges Crustaceer, med forelgbige Bamzrkninger over de
nye eller nimdre bekjendte Arter. Forh. Selsk. Christian., (1) :1-80.
1895. On some South-African Entomostraca raised from dried mud. Christian.
Selsk. Skr. I. Math.-nat. K1., (8) :1-56.
1896. On some West Australian Entomostraca raised from dried sand. Arch.
Math. Naturv., 19(1) :1-35.
1901. Contributions to the knowledge of the fresh-water. Entomostraca of
South America as shown by hatching from dried material. Arch.
Math. Naturv., 24(1) :1-52.
1926. Freshwater Ostracoda from Canada and Alaska. Report of the Canadian
Arctic Expedition, 1913-1918, 7(1) :1-22.
1928. An account of the Crustacea of Norway. Bergen, 9:i-xii, 1-277.
ScHLeErp, W. :
1909. Vergleichende Untersuchung der Eireifung bei parthenogenetisch und
bei geschlechtlich sich fortpflanzenden Ostracoden. Arch. Zellforsch.,
2:390-431.
ScHMALZ, J.
1912. Zur Kenntnis der Spermatogenese der Ostracoden. Arch. Zellforsch.,
8:407-441.
SCHREIBER, E.
1922. Beitrage zur Kenntnis der Morphologie, Entwicklung und Lebensweise
der Stisswasser-Ostracoden. Zool. Jb. Anat., 43:485-538.
SHANTZ, H. L.
1907. A biological study of the lakes of the Pike’s Peak region—preliminary
report. Trans. Amer. Micr. Soc., 27:75-97.
SHARPE, R. W.
1897. Contribution to a knowledge of the North American fresh-water Ostra-
coda included in the families Cytheridae and Cyprididae. Bull. Illi-
nois Lab. Nat. Hist., 4:414-482.
1903. Report on the fresh-water Ostracoda of the United States National
Museum, including a revision of the subfamilies and genera of the
family Cyprididae. Proc. U. S. Mus., 26:969-1001.
1908. Further report on the Ostracoda of the United States National Museum.
Proc. U. S. Mus., 35:399-430.
1910. On some Ostracoda, mostly new, in the collection of the United States
National Museum. Proc. U. S. Mus., 38:335-341.
1918. The Ostracoda. Ward and Whipple: Fresh-water Biology, 790-827.
SHELFORD, V. E.
1913. Animal communities in temperate America. University of Chicago
Press. i-xili, 1-368. (Second impression, 1937).
SKOGSBERG, TAGE
1920. Studies on marine Ostracods. Part I. Cypridinids, Halocyprids and
Polycopids. Zool. Bidr. Uppsala, suppl., 1:1-784.
SPANDL, HERMAN
1925. Die Tierwelt vortbergehenden Gewasser Mitteleuropas. Arch. Hydro-
biol., 16:74-132.
StorcH, O. |
1926. Uber den Fangapparat eines Ostrakoden. Verh. Dtsch. Zool. Ges., 2nd
suppl., 80-85.
1933. Morphologie und Physiologie des Fangapparates eines Ostrakoden (Noto-
dromas monacha). I, II, and III. Biol. Gen., 9(1) :151-198; 355-394;
(2) :299-330.
Strauss, HErcute E.
*1821. Mémoire sur les Cypris de la classe des Crustacés. Mem. Mus. Hist. nat.,
7:33-61.
174 ILLINOIS BIOLOGICAL MONOGRAPHS
Turner, C. H.
1892. Notes upon the Cladocera, Copepoda, Ostracoda and Rotifera of Cin-
cinnati, with descriptions of new species. Bull. Sci. Lab. Denison
Univ., 6:57-74.
1893. Additional notes on the Cladocera and Ostracoda of Cincinnati, Ohio.
Bull. Sci. Lab. Denison Univ., 8(1):1-18.
1894. Notes on American Ostracoda, with descriptions of new species. Bull.
Sci. Lab. Denison Univ., 8(2) :13-26.
1895. Fresh-water Ostracoda of the United States. Second Rep. State Zool.
Minnesota,’ 1895:277-337. (Contains a very extensive bibliography).
1896. Morphology of the nervous system of Cypris. J. Comp. Neurol., 6:20-44.
1899a. A male Erpetocypris barbatus Forbes. Zool. Bull., Boston, 2:199-202.
1899b. Synopsis of North-American invertebrates. V. Fresh-water Ostracoda.
Amer. Natural., 33:877-888.
UNvDERWooD, LucIEN M.
1886. List of the described species of fresh water crustacea from America,
north of Mexico. Bull. Illinois Lab. Nat. Hist., 2:323-386.
VAvRA, V.
1891. Monographie der Ostracoden Bohmens. Arch. naturw. Landesdf.
Bohmen, 8(3):i-iv, 1-116. (Contains a comprehensive bibliography).
1897. Die Sitisswasser-Ostracoden Deutsch-Ost-Africas. Tierwelt Deutsch-
Ostafrica. Wiss. Forsch. ttber Land und Leute uns. Ost-Afrik,
4:1-28.
WaAGLER, ERICH
1937. Crustacea. Die Tierwelt Mitteleuropas, 2(2a) : 1-224.
Warp, HELEN L.
1940. Studies on the life history of Neoechinorhynchus cylindratus (Van
Cleave, 1913) (Acanthocephala). Trans. Amer. Micr. Soc., 59:327-347.
WECKEL, Apa L.
1914. Free-swimming fresh-water Entomostraca of North America. Trans.
Amer. Micr. Soc., 33:164-203.
WEISMANN, AUGUST
1880. Parthenogenese bei den Ostracoden. Zool. Anz., 3:82-84.
WELCH, Paut S.
1935. Limnology. McGraw-Hill, New York. i-xiv, 1-471.
WIiLiIAMs, LEonarD W.
1907. A list of the Rhode Island Copepoda, Phyllopoda, and Ostracoda with
new species of Copepoda. 37th Ann. Rep. Comm. Fish. Rhode Island
(special paper no. 30), 69-79,
WOHLGEMUTH, R.
1914. Beobachtungen und Untersuchungen tiber die Biologie der Sisswasser-
ostracoden; ihr Vorkommen in Sachsen und Bohmen, ihre Lebens-
weise und ihre Fortpflanzung. Int. Rev. Hydrobiol., Biol. Supp.,
6:1-72.
Wotr, J. P.
1919. Die Ostracoden der Umgebung von Basel. Arch. Naturg., Abt. A,
85(3) :1-100.
WOLTERECK, R,
1898. Zur Bildung und Entwicklung des Ostrakoden-Eies. Z. wiss. Zool.,
64:596-623.
ZADDACH, E. G,
1844. Synopseos Crustaceorum Prussicorum Prodromus. Dissertatio zoologica.
Regiomonti (Konigsberg).
ZENKER, W.
1854. Monographie der Ostracoden. Arch. Naturg., 20(1) :1-87.
EXPLANATION OF PLATES
All drawings are from material collected in Illinois. A camera lucida was used
in every instance and, unless otherwise indicated, all drawings are made from
material mounted in diaphane and examined by transmitted light.
176 ILLINOIS BIOLOGICAL MONOGRAPHS
RiAgiih el
Cypricercus reticulatus (Zaddach 1844) Sars 1928; female.
Fic. 1—Animal with the left valve removed to show the appendages of the left
side in situ. Scale: 0.5 mm,
AN—Antenna P—Palp of mandible
AU—Antennule SH—Edge of right valve
E—Eye S—Sensory organ of antenna
F—Furca X—Maxilla
FB—Food balls R—First thoracic leg
G—Female genital lobe L—Second thoracic leg.
M—Mandible T—Third thoracic leg
N—Natatory or swimming setae V—Natatory or swimming setae_
of antennule of antenna a
Candona punctata Furtos 1933; female.
Fic. 2.—Outside view of the right valve. Scale: 0.5 mm.
Fic. 3.—Second thoracic leg. Scale: 0.1 mm. E—End claw. S—Second podomere.
Fic. 4.—Third thoracic leg. Scale: 0.1 mm. C—Shorter companion distal seta
of the similarly directed pair. P—Third or penultimate podomere.
Fic. 5—Furca and genital lobe. Scale: 0.1 mm. D—Dorsal seta. G—Genital lobe.
Candona fluviatilis sp. nov.; female.
Fic. 6.—View from inside of right valve. Scale: 0.25 mm.
Fic. 7—Shell sculpturing and muscle scars. M—Muscle scars (isolated ones not
indicated by letter). S—Sculpturing.
Fic. 8—View from outside of right antenna. Scale: 0.1 mm. S—Sensory organ.
Fic. 9.—First thoracic leg of right side. Scale: 0.1 mm. R—Setae representing
the respiratory plate.
OSTRACODS OF ILLINOIS—HOFF
177
PLATE I
178 ILLINOIS BIOLOGICAL MONOGRAPHS
PEATE AI
Candona fluviatilis sp. nov.; female.
Fic. 10.—Third thoracic leg. Scale: 0.05 mm. P—Penultimate podomere show-
ing undivided condition. S—Second podomere.
Fic. 11—Furca and female genital lobe. Scale: 0.1 mm.
G—Genital lobe T—Terminal claw
P—Dorsal seta’ V—Terminal seta
S—Subterminal claw
Candona simpsont Sharpe 1897; female.
Fic. 12—Outline drawings of the shells of several specimens. Scale: 0.5 mm.
Fic. 13—Third thoracic leg showing a combination of characters of the “simp-
soni’ form (as the spines on the margins of the antepenultimate and
penultimate podomeres) and the “exilis’ form (as the curved tip of the
shortest distal claw). Scale: 0.1 mm.
Fic. 14.—Furca showing an S-shaped subterminal claw. Scale: 0.1 mm. S—Sub-
terminal claw.
Fic. 15.—Furca showing a nearly straight subterminal claw, the dorsal thoracic
seta, and the genital lobe. Scale as in fig. 14. D—Dorsal thoracic seta.
G—Genital lobe.
Fic. 16—Furca showing straight and slender claws. Scale as in fig. 14.
Fic. 17.—Furca of an immature individual just before the molt in which the
third thoracic leg appears. The terminal seta of the furca is not de-
veloped. Scale: 0.05 mm. T—Terminal claw.
Candona albicans Brady 1864.
Fic. 18—View from outside of the right valve of female. Scale as in fig. 21.
O—Ovary.
Fic. 19.—End of the third thoracic leg of a female. Scale: 0.1 mm. P—Divided
penultimate podomere.
Fic. 20.—Furca of female. Scale: 0.1 mm.
Fic. 21.—Inside view of the right valve of male. Scale: 0.5 mm. T—Testis.
Fic. 22—Prehensile palps of male; (a) outside view of left palp; (b) inside
view of right palp. Scale: 0.025 mm.
Fic. 23—Penis. Scale: 0.1 mm.
Candona biangulata sp. nov.; female.
Fic. 24.—Inside view of the right valve (holotype). Scale: 0.25 mm.
Fic. 25.—Mandibular palp. Scale: 0.05 mm. B—Group of seta of antepenulti-
mate podomere. F—Basal podomere of palp or the second podomere of
the protopodite.
OSTRACODS OF ILLINOIS—HOFF
PLATE I
180 ILLINOIS BIOLOGICAL MONOGRAPHS
PVARE Lu
Candona biangulata sp. nov.; female.
Fic. 26.—Second thoracic leg (mounted in glycerine). Scale: 0.1 mm. A—Second
podomere. C—Distal claw. P—Penultimate podomere. U—vUltimate
or fifth podomere.
Fic. 27—Third thoracic leg (holotype). Scale: 0.5 mm.
Fic. 28.—Furca and genital lobe (holotype). Scale: 0.1 mm. G—Genital lobe.
Candona distincta Furtos 1933; female.
Fic. 29.—Outside view of left valve. Scale: 0.5 mm.
Fic. 30.—Furca and genital lobe. Scale: 0.1 mm. G—Genital lobe.
Candona crogmaniana Turner 1894; female.
Fic. 31—Inside view of right valve. Scale as in fig. 33.
Fic. 32.—Base of furcal ramus and genital lobe. Scale: 0.1 mm. G—Genital lobe.
Candona caudata Kaufmann 1900; female.
Fic. 33.—Inside view of left valve. Scale: 0.25 mm.
Fic. 34.—Distal portion of the third thoracic leg showing divided penultimate
podomere. Scale: 0.1 mm. P—Setae of similarly directed pair.
Fic. 35.—Furca and genital lobe. Scale: 0.2 mm.
Candona sigmoides Sharpe 1897.
Fic. 36.—Outside view of left valve of female. Scale: 0.5 mm.
Fic. 37—Furca and genital lobe of female. Scale: 0.2 mm.
B—Base or ramus of furca G—Genital lobe
C—Subterminal claw S—Terminal seta
D—Dorsal seta T—Terminal claw
Fic. 38.—Penis (mounted in glycerine). Scale: 0.2 mm.
Candona indigena sp. nov.
Fic. 39.—Lateral view of female from the left side (holotype; in alcohol). Scale
as in fig. 36. S—Swimming setae of antennules.
OSTRACODS OF ILLINOIS—HOFF
PLATE fil
181
182 ILLINOIS BIOLOGICAL MONOGRAPHS
PLATE AV
Candona indigena sp. nov.
Fic. 40.—View from ‘outside of right valve of female (paratype). Scale as in
fig. 41.
A—Anterior margin of shell O—Ovary
C—Pore-canals P—Posterior margin of shell
D—Dorsal margin of shell S—Ventral sinuation
M—Muscle scars V—Ventral margin
Fic. 41—View from outside of left valve of male (paratype). Scale: 0.5 mm.
T—Testis.
Fic. 42.—Dorsal view of female (holotype in alcohol). Scale as in fig. 41.
S—Swimming setae of antennules.
Fic. 43.—Mandible (holotype). Scale: 0.1 mm. C—Chewing edge. P—Penulti-
mate podomere. R—Branchial or respiratory plate. S—Setae bundle.
Fic. 44.—Distal podomeres of the second thoracic leg of male (allotype). Scale:
0.1 mm.
Fic. 45—Third thoracic leg of female (holotype). Scale: 0.1 mm.
Fic. 46.—Furca and female genital lobe (paratype) with furcal ramus extended
posteriorly. Scale as in fig. 45. G—Genital lobe.
Fic. 47—Prehensile palps (allotype); (a) right palp seen from the inside;
(b) left palp viewed from the outside. Scale as in fig. 45.
Fic. 48.—Penis (allotype). Scale: 0.1 mm. V—Vas deferens. O—Bifurcated
outer lobe.
Candona suburbana sp. nov.
Fic. 49.—Inside view of right valve of female (allotype). Scale: 0.5 mm.
Fic. 50.—Inside view of right valve of male (paratype). Scale as in fig. 49. .
Fic. 51.—Dorsal view of male (holotype; in alcohol). Arrow indicates the an-
terior end. Scale as in fig. 49.
Fic. 52.—Second thoracic leg of female (allotype). Scale: 0.1 mm.
Fic. 53—Third thoracic leg of male (holotype). Scale as in fig. 52. S—Setae of
the similarly directed pair. P—Divided penultimate podomere.
Fic. 54——Proximal portion of the furcal ramus and the genital lobe of the
female (allotype). Scale as in fig. 52. G—Genital lobe.
OSTRACODS OF ILLINOIS—HOFF
PLATE, IV
183
184 ILLINOIS BIOLOGICAL MONOGRAPHS
PLATE V
Candona suburbana sp. nov.
Fic. 55—Furca of male (paratype). Scale: 0.1 mm.
Fic. 56.—Prehensile palps of male (paratype); (a) inside view of the left palp;
(b) inside view of the right palp. Scale as in fig. 57.
Fic. 57.—Penis (paratype). Scale: 0.1 mm. I—Inner lobe of penis. M—Middle
lobe of penis. O—Outer lobe of penis. V—Vas deferens.
Candona fossulensis sp. nov.
Fic. 58.—Inside view of left valve of female (holotype). Scale: 0.5 mm.
Fic. 59.—Markings on posterior slope of shell of female (paratype). Scale as in
fie 55:
Fic. 60.—Mandibular palp of female (paratype). Scale: 0.1 mm. S—Bundle of
setae of antepenultimate podomere.
Fic. 61—Third leg of female (paratype). Scale as in fig. 57.
Fic. 62.—Furca and genital lobe of female (paratype). Scale as in fig. 55.
Fic. 63.—Prehensile palps of male (allotype) ; (a) outside view of right; (b) out-
side view of left. Scale as in fig. 57.
Fic. 64.—Penis of male (paratype). Scale: 0.2 mm.
Candona acuta sp. nov.
Fic. 65.—Inside view of right valve of female (holotype). Scale: 0.5 mm.
Fic. 66.—View from ventrad of the left valve of female (holotype in alcohol).
Arrow indicates anterior end. Scale as in fig. 65.
Fic. 67.—Second leg of female (paratype). Scale: 0.1 mm. F—First podomere.
P—Penultimate podomere. S—Second podomere.
Fic. 68.—Third leg of female (paratype). Scale: 0.1 mm. P—Parts of the
divided penultimate podomere.
Fic. 69.—Furca of the female (holotype). Scale: 0.1 mm.
B—Seta of dorsal-posterior R—Ramus of furca
part of the thorax S—Terminal seta
D—Dorsal seta of furca T—Terminal claw
G— Genital lobe U—Subterminal claw
OSTRACODS OF ILLINOIS—HOFF
PLATE V
185
186 ILLINOIS BIOLOGICAL MONOGRAPHS
- : PLATE VI
Candona acuta sp. nov.
Fic. 70.—Inside view of left valve of male (allotype). Scale: 0.5 mm.
Fic. 71.—Prehensile palps of the male (paratype) ; (a) inside view of left palp;
(b) inside view of right palp. Scale: 0.1 mm.
Fic. 72—Penis (allotype). Scale: 0.2 mm. I—Inner lobe. M—Middle lobe.
O—Outer lobe.
Cyclocypris forbesi Sharpe 1897; female.
Fic. 73.—Inside view of left valve of shell. Scale: 0.25 mm.
Fic. 74—Second thoracic leg. Scale: 0.1 mm.
Fic. 75—Third thoracic leg. Scale as in fig. 74.
Cypria turnert sp. nov.
Fic. 76.—View of the left side of the female (paratype in alcohol). Scale:
0.25 mm. A—Swimming setae of antennae. E—Eye. M—Muscle scars.
S—Swimming setae of antennules.
Fic. 77.—Ventral view of the left valve of female (in alcohol). The arrow
points toward the anterior end.
Fic. 78.—Characteristic markings on the shell. Scale: 0.025 mm.
Fic..79.—Furca of male (paratype). Scale: 0.1 mm.
Fic. 80.—Prehensile palps of the male (allotype) ; (a) left palp seen from inside;
(b) right palp viewed from outside. Scale as in fig. 79. D—Dactylus.
P—Propodus.
Fic. 81—Penis of male (paratype). Scale as in fig. 79. I—Inner lobe. M—Middle
lobe.
Cypria mediana sp. nov.
Fic. 82.—Outside view of right valve of female (paratype). Scale: 0.5 mm.
Fic. 83.—Ventral view of left. valve of female (holotype in alcohol). Arrow
indicates the anterior end. Scale as in fig. 82.
Fic. 84.—Third thoracic leg of female (holotype). Scale: 0.1 mm.
Fic. 85.—Furca of female (paratype). Scale as in fig. 84.
Fic. 86.—Inside view of right valve of male (allotype). Scale as in fig. 82.
Fic. 87—FPenis (allotype). Scale as in fig. 84.
OSTRACODS OF ILLINOIS—HOFF
PLATE VI
187
188 ILLINOIS BIOLOGICAL MONOGRAPHS
PEA Evil
Cypria obesa Sharpe 1897; female.
Fic. 88 —lInside view of right valve. Scale: 0.5 mm.
Fic. 89.—Distal portion of the third thoracic leg. Scale: 0.1 mm.
Cypria maculata sp. nov.
Fic. 90.—Inside view of left valve of female (holotype). Scale: 0.25 mm.
Fic. 91—Third thoracic leg of female (paratype). Scale as in fig. 89.
Fic. 92—Furca of female (holotype). Scale as in fig. 89.
Fic. 93.—Ductus ejaculatorius of the male. Scale as in fig. 89.
Fic. 94—Prehensile palps of male: (a) outside view of left palp; (b) inside
view of right palp. Scale: 0.05 mm.
Fic. 95—Penis. Scale as in fig. 94. I—Inner lobe. M—Middle lobe.
Cypria ophthalmica (Jurine 1820) Brady and Norman 1889; female.
Fic. 96—Animal viewed from left side. Scale: 0.25 mm.
Fic. 97.—Pattern of color markings on the shell. Scale: 0.05 mm.
Physocypria pustulosa Sharpe 1897; female.
Fic. 98.—Right valve viewed from the inside. Scale as in fig. 96.
Ilyocypris gibba (Ramdohr 1808) Brady and Norman 1889; female.
Fic. 99—Right valve seen from the outside. (Sculpturing shown only on the
posterior part of the shell.) Scale: 0.5 mm. F—Furrows. M—Flat-
tened margin. P—Protuberances.
Fic. 100.—Second thoracic leg. Scale: 0.1 mm.
Ilyocypris bradyi Sars 1890; female.
Fic. 101.—Left valve seen from outside. (Shell sculpturing shown only on pos-
terior part of shell.) Scale as in fig. 99.
Fic. 102—Distal portion of the second thoracic leg (mounted in glycerine).
Scale as in fig. 100. P—Two divisions of the penultimate podomere.
Cypricercus tuberculatus (Sharpe 1908) comb. nov.
Fic. 103—Outside view of right valve of female. Arrow indicates anterior end.
Scale: 0.5. mm.
Fic. 104—Penis. Scale: 0.1 mm.
Cypricercus reticulatus (Zaddach 1844) Sars 1928.
Fic. 105—Outside view of the right valve of female. Scale: 0.5 mm.
189
OSTRACODS OF ILLINOIS—HOFF
PLATE Vii
190 ILLINOIS BIOLOGICAL MONOGRAPHS
PLATE. VIII
Cypricercus reticulatus (Zaddach 1844) Sars 1928.
Fic. 106.—Portion of the antenna of the female. Scale: 0.1 mm. A—Antepenulti-
mate podomere. B—Seta with bulbous base. O—Sensory organ.
S—Swimming setae.
Fic. 107.—Furca of female. Scale: 1.5 mm.
Fic. 108.—Outline drawing of the shell of the male. Arrow indicates the anterior
end. A—Anterior portion of testis. P—Posterior portion of testis.
Fic. 109.—Penis. Scale as in fig. 106. L—Middle lobe. V—Vas deferens.
Cyprinotus incongruens (Ramdohr 1808) Turner 1895; female.
Fic. 110.—Inside view of right valve. Scale: 1.0 mm.
Fic. 111.—Furca. Scale: 0.5 mm.
Notodromas monacha (O. F. Miller 1776) Lilljeborg 1853; male.
Fic. 112.—Outside view of the left valve. Arrow indicates the anterior end.
Scale: 0.5 mm.
Fic. 113—Outer masticatory process of the maxilla. Scale: 0.05 mm.
Fic. 114—Furca. Scale: 0.25 mm..
Cypridopsis vidua (O. F. Miller 1776) Brady 1867; female.
Fic. 115—View of left side. Arrow indicates the anterior end. Scale: 0.5 mm.
Fic. 116—Anterior margin of the right valve to show the tubercles. Scale:
0.1 mm.
Fic. 117—Furca. Scale: 0.1 mm. F—“Flagellum.”
Potamocypria smaragdina (Vavra 1891) Daday 1900.
Fic. 118—Female viewed from the right side. Scale: 0.25 mm. C—Claws of
second thoracic legs. S—Swimming setae of antennae.
Fic. 119—End of maxillary palp to show distally widened ultimate podomere.
Scale: 0.025 mm.
Fic. 120.—Outside view of terminal end of the right third thoracic leg to show
the chela or “pincers apparatus.”
Fic. 121—Outside view of left valve of the male. Arrow points to the anterior
end. Scale: 0.25 mm. A—Anterior portion of the testis. F—Anterior
flange of shell.
Fic. 122.—Prehensile palps of the male; (a) outside view of the left palp;
(b) inside view of the right palp. Scale: 0.05 mm. D—Dactylus.
P—Propodus.
Fic. 123.—Ductus ejaculatorius of male. Scale as in fig. 122. V—Vas deferens.
Fic. 124—Penis. Scale: 0.1 mm.
191
OSTRACODS OF ILLINOIS—HOFF
PLATE VIII
192
ILLINOIS BIOLOGICAL MONOGRAPHS
PAE aX
Darwinula stevenson (Brady and Robertson 1870) Brady and Norman 1889; female.
Fic
Fic
. 125 —Inside of left valve. Scale: 0.25 mm.
. 126.—End of thorax. Arrow points ventrally. Scale: 0.05 mm.
Limnocythere verrucosa sp. nov.
Fic
Fic
Fic
. 127—Outside view of right valve of female. (Sculpturing omitted.) Scale
as in fig. 125. K—Furrows. M—Anterior margin with pore-canals.
P—Protuberances. S—Muscle scars.
. 128.—A portion of the anterior margin of the shell. Scale: 0.1 mm.
H—Setae. P—Pore-canals. S—Sculpturing. T—Tubercles.
. 129.—Shell of female from above. Arrow indicates the anterior end. Scale
as in fig. 125.
Fic. 130.—End of the antennule of the female to show the terminal and subter-
Fic
Fic
Fic
Fic
Fic
minal setae. Scale as in fig. 126. F—Fused portion of terminal setae.
. 131—View from the outside of the left antenna of the female. Scale: 0.1
mm. A—Articulation of parts of “flagellum.” F—Basal portion of
“flagellum” or exopodite. T—Antepenultimate podomere or first
podomere of the endopodite.
. 132—Furca of female. Scale: 0.025 mm. P—Papilla with dorsal seta.
. 133—Outside view of right valve of male. (Surface markings not shown.)
Scale as in fig. 125.
. 134—Outside view of right penis. Scale: 0.1 mm. F—Furca.
. 135 —“Brush-form” sensory organ of male. Scale: 0.05 mm. B—Pedicel to
to which organ is attached. S—Distal setae.
Limnocythere reticulata Sharpe 1897.
Fic. 136.—Inside view of the left valve of the female. Scale: 0.5 mm.
Fic
Fic
. 137.—Anterior and posterior ends of inside of the dorsal margin of the right
valve of female to show the teeth. (Center of dorsal margin omitted.)
AT—Anterior teeth. PT—Posterior teeth.
. 138—Furca of female. Scale: 0.05 mm. D—Dorsal seta.
Fic. 139—Third thoracic leg of the male. Scale: 0.1 mm.
Fic
Fic
. 140—Shell of male viewed from the right side. Scale as in fig. 136.
. 141.—Penis in outside view from the left. Scale: 0.25 mm.
OSTRACODS OF ILLINOIS—HOFF 193
PLATE IX
INDEX
The names of new species are printed in bold-face type. The names of
other species known from Illinois and the page numbers referring to
specific diagnoses are given in ttalics.
Abdomen, 42, 46
Acanthocephala, parasitic on ostracods,
10
acuminata, Candona, 70, 73
Acuminata, group of genus Candona, 55,
73-75
acuta, Candona, 16, 23, 25, 27, 28, 30, 34,
37, 40, 56, 57, 75, 82, 95, 96-100
aemonae, Candona, 73
affinis, Cypris, 139, 141
albicans, Candona, 16, 23, 25, 27, 30, 33,
34, 37, 40, 66, 67-69, 72
Antenna, 43
Antennules, 43
Appendages, 42-46
Associations between ostracod species,
32
aurea, Argilloecia, 157
aurea, Darwinula, 158
Bairdia, genus, 51
Bairdiidae, family, 51
biangulata, Candona, 16, 23, 25, 27, 30,
33, 34, 36, 40, 66, 67, 70-73
bilobata, Candona, 72
Biotic relationships, 29-33
Body segmentation, 42
bradii, Ilyocypris, 130
brady, Ilyocypris, 16, 23, 25, 27, 28, 30,
34, 37, 40, 127, 128, 130-131
“Brush-form” organ, 46
burlingtonensis, Cyprinotus, 135, 136, 137
burlingtonensis, Cypris, 135, 136, 137, 138
Candida, group of genus Candona, 55
Candocypria, genus, 101
Candocyprinae, subfamily, 52, 101
Candona, genus, 54-57
Candoninae, subfamily, 52-53
Candoninae s. str., subfamily, 52, 53-54,
101
caudata, Candona, 16, 23, 25, 27, 34, 36,
40, 56, 57, 74, 80-82, 92, 98
Cephalic appendages, 42-45
Chela of third leg, 46
cingalensis, Cyprinotus, 136
Circulatory system, 47
Cladocopa, suborder, 50
Cleaning foot, 46
Color of shell, 32-33
Compressa, group of genus Candona, 55,
56, 66-67
compressa, variety of
smaragdina, 154, 156
copiosa, Entocythere, 16, 166
Copulatory organs, 48-49
crogmani, Candona, 79-80
crogmaniana, Candona, 16, 23, 24, 27, 34,
37, 40, 56, 74, 79-80
Cryptocandona, group of genus Can-
dona, 55
Cyclocyprinae, subfamily, 52-53, 100-101
Cyclocypris, genus, 101-102
Cypria, genus, 101, 104-105
Cypricercus, genus, 132-133
Cypridae, family, 51-53
Cypridopsinae, subfamily, 52-53, 132, 150
Cypridopsis, genus, 150-151
Cyprinae sensu lato, subfamily, 52, 132
Cyprinae s. str., subfamily, 52-53, 131-132
Cyprinotus, genus, 132, 143
Cyprois, genus, 147, 149
Cytherella, genus, 51
Cytherellidae, family, 50
Cytheridae, family, 51, 159
Potamocypris
Darwinula, genus, 157
Darwinulidae, family, 51, 157
decora, Candona, 91, 95
dentifera, Cypria, 125, 127
dentifera, Physocypria, 16, 37, 40, 116-
117, 120-121, 125-127
Digestive system, 47
distincta, Candona, 16, 23, 24, 27, 33, 34,
37, 40, 56, 57, 74, 77-78, 91
Distribution, 25-29, 39-41
Ductus ejaculatorius, 48
Egg-laying, 37-38
elegantula, Cypria, 106, 107, 108-109
elongata, Candona, 80, 88, 91-92
Entocythere, genus, 166
Entocytherinae, subfamily, 159, 166
eriensis, Candona, 91
Eucypris, genus, 133
Excretory system, 47
exculpta, Cypria, 38, 106, 109
exilis, Candona, 62, 65, 66
Exopodite of antenna, 43, 51
exsculpta, Cypria, 22, 29, 106, 108-110
Eyes, 43
194
OSTRACODS OF ILLINOIS—HOFF . 195
fabaeformis, Candona, 76-77, 100
Fabaeformis, group of genus Candona,
55, 100
fasciata, Cypris, 35
fasciata, Dolerocypris, 35
Feeding, appendages, 44-45
fluviatilis, Candona, 16, 23, 24, 27, 28,
33, 34, 36, 40, 56, 57, 58, 60-62
Food of ostracods, 38-39
forbest, Cyclocypris, 16, 23, 24, 27, 31,
32, 34, 37, 40, 102-103
fossulensis, Candona, 16, 23, 24, 27, 33,
34, 37, 40, 56, 57, 75, 92-95, 98
Furca, 46
Furcal ramus, 43, 46
fuscata, Cypris, 135, 136, 137, 138, 139,
142
fuscatus, Cypricercus, 17, 36, 40, 133,
135-138
fuscatus, Monoculus, 135
gibba, Cypris, 128
gibba, Ilyocypris, 16, 23, 25, 27, 28, 30,
34, 37, 40, 127, 128-130, 131
gigantica, variety of Eucypris fuscata,
15," 137
globula, Physocypria, 10, 121-125
Habitats, 21-29
Heart, 47
Herpetocypridinae, subfamily, 52
herricki, Cypris, 35, 36
hertzogi, Candona, 72
hirsuta, Eucypris affinis, 139, 140, 141,
142, 143
hirsutus, Cypricercus affinis, 142
horridus, Cypricercus, 135
Hydrogen ion concentration, 28-29
Iliocyprella, genus, 127-128
illinotsensis, Entocythere, 16, 166
illinoisensis, Limnicythere, 165
illinoisensis, Limnocythere, 17, 37, 40,
161, 162, 165-166
Ilyocyprinae, subfamily, 52-53, 127-128
Ilyocypris, genus, 127-128
improvisa, Darwinula, 158
incisa, Chlamydotheca, 36
incongruens, Cyprinotus, 17, 23, 25, 26,
27, 28, 30, 34, 35, 37, 38, 40, 46, 143,
144-145, 146-147
incongruens, Cypris, 144
indigena, Candona, 16, 23, 24, 27, 33, 34,
37, 40, 56, 57, 75, 85-88, 98
labiata, Chlamydotheca, 36
labiata, Cypris, 36
laevis, Cyclocypris, 103-104
lapponica, Candona, 87-88
Larval development, 35-38
levanderi, Candona, 87-88
Limnicythere, genus, 160
Limnocythere, genus, 160-161
Limnocytherinae, subfamily, 159-160
Macrocyprinae, subfamily, 52
maculata, Cypria, 16, 23, 25, 27, 29, 30,
33, 34, 37, 40, 105, 114-117, 119, 126-
127
major, variety of Cypris fuscata, 135,
137
Mandibles, 44
marginata, Cypris, 149
marginata, Cyprots, 15, 17, 37, 40, 41,
149-150
Masticatory processes, 44, 45
Maxilla, 44
Maxillary foot, 45
Maxilliped, 45
mediana, Cypria, 16, 23, 25, 27, 28, 34,
37, 40, 41, 105, 110-112
Methods of collection and study, 17-21
minor, variety of Cypris fuscata, 137,
139-140
Mixta, group of genus Candona, 55
monacha, Cypris, 148
monacha, Notodromas, 15, 17, 23, 24, 27,
34, 37, 38, 40, 41, 148-149
monachus, Notodromas, 148
Myodocopa sensu lato, order, 50
Myodocopa s. str., order, 50
Nauplius, 35
neglecta, Cypria, 119
Nervous system, 47-48
Nesidea, genus, 51
Nesideidae, family, 51
Notodromas, genus, 147, 148
Notodrominae, subfamily, 52-53, 132, 147
obesa, Cypria, 16, 23, 25, 27, 30, 33, 34,
37, 40, 105, 112-114
obesa, Cypridopsis vidua, 151, 152
Ontogeny, 35-36
ophthalmica, Cypria, 16, 23, 24, 27, 28,
29, 30, 31, 33, 34, 37, 40, 105, 108,
114, 116-117, 117-120
ophthalmicus, Monoculus, 117
opthalmica, Cypria, 114, 117
Ostracoda, order, 49
Ostracoda, suborders of, 49-50
Ovary, 48
ovum, Cyclocypris, 35
ovum, Cypris, 35
Palps, 44, 45
Paracandona, genus, 54
parallela, Candona, 66, 67-69
196 ILLINOIS BIOLOGICAL MONOGRAPHS
Parasites of ostracods, 10
pellucida, Cypris, 146
pellucida, Cyprinotus, 144, 146-147
pellucidus, Cyprinotus, 17, 36, 40, 143,
145, 146-147
Penis, 48-49
Physocypria, genus, 101, 120-121
Plankton, 29-30
Plants, relation of ostracods to, 30-32
Platycopa, suborder, 50
Podocopa sensu lato, suborder, 50-51
Podocopa s. str., suborder, 49-51
Pontocyprinae, subfamily, 52
Potamocypris, genus, 150, 153
punctata, Candona, 16, 23, 24, 27, 33, 34,
37, 40, 41, 56, 57, 58-60
pustulosa, Cypria, 29, 121
pustulosa, Cypridopsis, 151-153
pustulosa, Physocypria, 10, 11, 16, 23, 24,
Zi28 29. 30) 32.33, 34,37, 40120;
121-125
recticauda, Candona, 16, 37, 40, 56, 57,
74, 75-76
reflexa, Candona, 62, 65
Reproduction, 36-38
Reproductive system, 48-49
Respiration, 46
reticulata, Cypris, 139
reticulata, Limnicythere, 163
reticulata, Limnocythere, 17, 23, 25, 27,
28, 29, 30, 32, 34, 37, 40, 161, 163-165
reticulatus, Cypricercus, 17, 23, 24, 26,
27-30, .33: 34,36, 37, 38, 40, 1335 137;
138, 139-143
Rostrata, group of genus Candona, 55,
57-58
scopulosa, Candona, 91
Seasonal distribution, 33-34
Sensory organs, 43, 48
sharpei, Candona, 16, 37, 40, 56, 74,
76-77, 100
sharpet, Cyclocypris, 16, 37, 40, 103-104
Shell, morphology, 41-42
sigmoides, Candona, 16, 23, 24, 27, 28,
34, 37, 40, 56, 74, 82-84, 98
simpson, Candona, 16, 23, 25, 27, 29, 30,
33, 34, 36, 40, 56, 57, 58, 62-66
smaragdina, Cypridopsis, 154
smaragdina, Potamocypris, 17, 23, 25, 26,
27, 28, 29, 30, 31, -32ase eee,
39, 40, 153, 154-157
speciosa, Chlamydotheca, 35
Spirocypris, genus, 134-135
stagnalis, Candona, 68
stevensom, Darwinula, 15, 17, 23, 24, 27,
34, 37, 40, 41, 157-159
stevensoni, Polycheles, 158
striolata, Cypria, 106
suburbana, Candona, 16, 23, 24, 27, 33,
34, 37, 40, 56, 57, 75, 88-92, 98
Tactile sense organs, 48
Testes, 48
testudinaria, Cypris, 139, 140-141
Thoracic appendages, 45-46
tuberculata, Spirocypris, 133-135
tuberculatus, Cypricercus, 16, 23, 24, 27,
33, 34, 37, 40, 41, 133-135
turneri, Cypria, 16, 22, 23, 25, 27, 29, 30,
33, 34, 37, 38, 40, 105, 106-110
verrucosa, Limnocythere, 17, 23, 24, 27,
31, 34, 37, 40, 41, 160, 161-163
vidua, Cypridopsis, 11, 17, 23, 25, 27, 28,
29, 30,31, 32, 33, 34, 36, desea:
151-153
vidua, Cypris, 151
Zenker’s organ, 48
il
|
i
—
——
—
———
———
=———S=
_
——
—
——T=
————
st
eS
_————
———___t
oO
<
TT
~
oO
©
w
o
oO
N
T
Ld
oO
oP]
Wi
|
————
Live Music Archive
Librivox Free Audio
Metropolitan Museum
Cleveland Museum of Art
Internet Arcade
Console Living Room
Books to Borrow
Open Library
TV News
Understanding 9/11