THE GEOLOGICAL AND NATURAL HISTORY SURVEY OF MINNESOTA.
N. H. WiNCHELL, State Geologist.

w"

0

A FINAL REPORT

ON THE

M

V^Ai

L

iV

Crustacea of Minnesota

INCLUDED IN THE ORDERS

CLADOCERA AND COPEPODA.

Together with a synopsis of the described species in North America, and keys
to the 1- ^ojvn. species of the more important genera.

By C. L. HERRICK, Assistant in Zoology.

MINNEAPOLIS :

JOHNSON, SMITH & HARRISON.
1884.

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1^3 4

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PREFACK

N presenting Avhat may be denominated a final report of the work
cnq) done in this state upon the group of Crustacea best repre-
sented, and, all things considered, most important, the author must
admit that the term '' final " refers only to his own opportunities
and the limitation of time imposed by circumstances.

While a comparatively large proportion of all the species exist-
ing within our limits have been examined during the progress of
these investigations, there undoubtedly remain many additional
and curious forms to reward the search of the student. A great
variation in the degree of completeness with which the diflferent
genera and species have been treated will be observed, due in part
to the circumstances under which they were studied, and frequently
to the poverty of material. The entomostracean fauna is quite
different at different seasons, and a complete knowledge of even
our local fauna requires a long period of observation. Even the
dead of winter is a favorable time to study some groups. The late
autumn is, perhaps, the most favorable opportunity; for then, in
one group, the sexual activities are just at their height, and both
sexes may be studied. A number of cladocera are restricted to this
season. There are a number (how large it is not yet possible to
tell) of species in both groups which are to be sought by night
though no phosphorescent species are yet known. Our larger,
and, especially, deeper lakes have a quite diff'erent fauna from the
shallow pools and rirers. In general, the flowing waters are poor
in entomostraca. The cladocera or shelled entomostraca, have here
received a large share of attention, and more particularly the Lyn-
ceidse, which are the most minute of arthropods. This study has
been rewarded with an unexpectedly large number of forms, and a
particularly large number of species identical with those of Europe
and elsewhere. Prof. Birge is the only American writer who
has attempted this group, and his valuable work has made us
familiar with the more striking new species. A few new species
are included in our list and several varieties hardly yet known in
Europe. The remarkable Monospilius is among these. This ani-
mal has but a single larval eye in the middle of its forehead, and

4: TWELFTH ANNUAL REPORT.

wears its old covering over the newly-formed shell till the latter
is a curious patchwork mass. The attempt has been made to in-
corporate a brief description of all American species with those
found in Minnesota, and also to frame keys for the larger genera,
so that the place of a species among its congeners may, at least
approximately be found. The difficulty of framing such keys is
very great ; for few authors have employed the same distinctions
in their descriptions, and it is necessary to select points sharply
distinctive and conspicuous from the often meagre remainder after
striking off scattering particulars. In some cases this difficulty
has been greatly enhanced by the possibility that some of the
species should be considered synonyms or varietal forms. The
tendency to combine questionable forms thus produced it was
necessary to offset by what may seem a too great conservatism.
Faulty, however, as these keys may be, it is hoped that they will
serve a good purpose in the extent which they cover. While the
limits of this work preclude much more than a systematic outline,
opportunity is taken here and there to admit a word on the
anatomy or development. Such allusions must be considered
simply accidental, for a complete treatment of these subjects would
require large volumes, and the material will be long in gathering.
A larger proportion of the rare males of the cladocera are here
referred to than in any previous work of equal extent. The genus
Cyclops, one of the bugbears to fresh-water carcinologists, is per-
haps somewhat summarily treated. The excuse must be the con-
dition of the synonomy. However, most of the combinations made
were the result of careful study of large series from different locali-
ties. The sketches illustrating this paper are photo-printed from
the writer's own drawings, and, without the elegance of litho-
graphs, serve the purpose of explaining points of structure which
cannot be communicated verbally. I am indebted to Prof. A. S.
Forbes for very timely aid in bibliography, without which the
paper could not have been completed. To Dr. Lindthal, through
my friend Mr. Oe&tlund, I am indebted for a like service. But my
obligation is (ftepest to Prof. Rudolph Leuckart of Leipzig, who
kindly afforded access to almost a complete set of works on Euro-
pean entomostraca. Prof. C. W. Hall has collected at much
expenditure of time and labor a set of specimens from different
parts of the state which he kindly placed in my hands, thus en-
abling me to observe the great similarity of widely-separated
faunae. Mr. Lieberg also sent specimens of Diaptomus stagnalis
from saline pools in Dakota.

STATE GEOLOGIST.

INTRODUCTORY,

" Evading e'en the microscopic ej'e,

Full nature swarms witli life ; one wondrous mass

Waitintc the vital breath, when Parent Heaven

Shall bid the spirit blow. The hoary fen,

In putrid streams, emits the living cloud

Of pestilence. Through subterranean cells,

Where searching sunbeams scarce can And a waj',

Earth animated heaves. The flowery leaf

Wants not its soft inhabitants. Secure

Within its winding citadel, the stone

Holds multitudes. * * where the pool

Stands mantled o'er with green, invisible

Amid the floating verdure, millions stray.

* * Nor is the stream

Of purest crystal, nor the lucid air.

Though one transparent vacancy it seems,

Void of their unseeu people."— Cou'per.

To the poet only, and the man of science, is it given to meet
these "unseen people" on those familiar terms which warrants the
use of the word intimacy; yet may not we who, like Sam Weller,
find our "vision limited," because we have only eyes, avail our-
selves of the kind introduction these people give us, and shake
hands, as it were, though perhaps a little stiffly, with our neigh-
bors, the unseen people.

Whether we like it or not — Cowper intimates we shall not —
these people, in one way or another, touch us constantly, and like
diminutive sprites are ever active in hatching mischief or doing
their little favors to humanity. Happily most of these are amiable
goblins, and are tireless in endeavors to secure us against our
insidious enemies of their own ilk. With your permission we will
draw the curtain which separates us from the naiades of our pools
and streams.

The numbers of living forms to be found in any pool is a con-
stant surprise even to the student of this subject, and the variety
and unique character of the animals, particularly, cause a constant
flow of wonder and admiration. Confining ourselves to the crus-

6 TWELFTH ANNUAL REPORT.

tacean forms which are, perhaps, most typical, abundant and
interesting of the smaller animals of fresh waters, it is to be re-
marked that they are of a practical value to an extent which can
hardly be correlated with their seeming insignificance.

To understand this fact it is first necessary to recollect that
water in some form is an indispensable vehicle for the nidus of
disease germs as well as of all life; desiccation means death. The
abundantly-watered portion of our country must become per-
meated with the pestilential hordes ingendered in its fens did not
this army of devouring animalcuIoB destroy the decaying matters
accumulating in the vv^aters.

Their importance depends largely on their minute size and un-
paralleled numbers. The majority of non-carnivorous crustaceans
are so constituted that their diet is nearly confined to such floating
particles of matter as are present in the water, in a state of more
or less fine comminution; for, nearly without prehensile organs,
these animals, by means of a valvular or, at most, ladle-like labrum,
dip from the current of water kept flowing by the constant
motion of the branchial feet, such fragments as the snail and
scavenger-fish have disdained. All is fish which enters the net.
Think of it, poor dyspeptic, a constant supply of food of every
variety and no question asked for stomach's sake!" Bits of decay-
ing algae or the broken fragments of a disintegrated mosquito, all
alike acceptable and unhesitatingly assimilated.

Nor is the sanitary aspect the only one in which the entomost-
raca, as our minute Crustacea are collectively called, command
attention; they are valuable also as a food supply.

Now, does some one jump at the conclusion that the water we
drink is filled with aliment in such pleasant form as that repre-
sented above — that Dr. Tanner after all lived on a watery solution
of entoniostraca? Too fast, my friend — food for fishes, but not
therefore an insignificant element in our cuisine economy; for it
has recently been shown by Prof. Forbes of Illinois, that some of
our best fresh-water food fishes are almost dependent on some one
or more species of entomostraca. Darwin shows that cats regulate
the clover crop of England via field-mice and humble-bees, but it
is not half as far from our ''bugs" to the price of trout and white-
fish.

Still we are not prepared to be surprised at this, for have we not
long understood that whales go fishing, with their whalebone nets,
for little moUusks not big enough to excite the cupidity of the
orial small boy?

STATE GEOLOGIST. 7

The fact is, that the principle laid down by the Deacon (of
venerable memory) that ''the weakest pint must stand the strain/^
maintains in nature aside from the nature of "shays." The minutest
forms are in some sense the most important, for they are the links
wliich stand nearest the rock, and it they be loosened the depen-
dent series falls.

The animals of the above group are, it is likely, the best criteria
by which to judge of the purity of natural waters if their distribu-
tion were correctly understood. The presence of some species in
great numbers is sufficient evidence of organic impurity. A criti-
cal study of the contents of samples of such waters will enable us
to determine their character almost as well as by analysis. The
following list of the animal life visible in a quart of filthy pond-
water, taken by simple dipping, will perhaps be suggestive on this
point:

Daphnia pulex 6

Cerioclaphnia 1400

Simoccplialus 56

Cypris.. 50

Cyclops 30

Sand-fleas 120

Total Crustacea 1662

Infusoria 35

Arachnida {Hydrachna) 1

Vermes . 5

Insecta—

Coleoptera (larvae) 8

Diptera (larvae) 11

Hemiptera 10

Mollusca 35

Total n 1767

The above are simply the animal forms visible to the (trained)
unassisted eye; the truly microscopic forms number vastly more.

But each gathering includes specimens of carnivorous entomost-
raca as well, and these are not less interesting and bizarre than the
cladocera.

The common cyclops, busy picking the bones of a luckless pol-
liwog (must we say pnrwiggy?), is not less benevolent than the
animate filters mentioned above. The amount of such material
that they will dispose of in a short period of time is truly astonish-
ing. It is the province of the following chapters to describe
briefly such of these animals as fall in the two groups Cladocera
and Copepoda and have been noticed in America.

g^MTi

S H,

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8 TWELFTH ANNUAL REPOKT.

CHAPTER I.

THE ENEMIES OF ENTOMOSTRACA.

First among these rank the young of various fishes which prey
upon, and find their entire support in, these minute animals. This
subject has been fully treated by Forbes, Ryder and others.

The enemy next most dreaded by entomostraca is, perhaps, the
"spectre animalcule" or the larva of the little frost-gnat, corethra.
It is no unusual thing to see a corethra carefully gorging itself
with a fat cyclops, suddenly seized by the protractile jaws of the
dragon-fly larva, shaken for a minute and then engulfed in the
tomb-like cavernous mouth below. Nor is the road to the
stomach of the dragon-fly always so circuitous. Water-tigers also,
with other larvte, prey upon these unfortunates. The hydra con-
siders them a dainty morsel, and at once paralyzes them by the
touch of his nematocystiferous arms; in other words, by the pois-
onous barbs coiled in concealment in the cells of the tentacles.

If the animal flys from these ubiquitous enemies he almost cer-
tainly is betrayed by carnivorous plants which abound in all our
waters. Forbes says: "In ten bladders of Utriculai^is vulgaris, taken.
at random, 1 found 93 animals, either entire or in recognizable
fragments, and representing at least 28 species. Seventy-six of
the animals found were entomostraca, and belonged to 20 species."
"Just one-third of all the animals found in these bladders belonged
to the single species Acroperus leucocephalus, Koch."

But among the ranks of enemies must be included certain para-
sites, both external and internal, of which a variety are known.
A few of the most remarkable of these will be mentioned. I may
be permitted to quote from an article in the American Naturalist,
April, 1883:

"We have discussed the relation of the minute fresh-water Crus-
tacea to sanitary science in a paragraph in a recent article in the
Naturalist, but it remains to touch upon another phase of the
subject. It may be thought unnecessary to trouble ourselves

STATE GEOLOGIST. 9

about the pathological conditions prevailing among such lowly-
animals, but it can be shown that these same causes of disease may
not be unimportant in connection with human diseases.

Tt is a fact constantly receiving new exemplification, that the
parasites infesting small animals, particularly water animals, are
frequently but the immature forms of parasites of animals higher
in the scale. These alternating generations are exceedingly diffi-
cult to study, so that while all stages may be separately known,
only a fortunate combination of circumstances or patient accumu-
lation of facts can connect the individual factors into the complete
cyclus.

Thus, for example, Prof. Leuckart has but recently worked out
the full life-history of Distomum hepaticum, although the adult
has been a stcek example in helminthological study in the labor-
atory for years.

The importance of such parasites, even in a commercial view,
needs but a reference to trichinosis to illustrate. I am not aware
that endo-parasites are known in entomostraca except in the case
of Cyclops. Embryos of Cucullanus elegans, a nematoid worm,
enter the body cavity of cyclops and undergo two moults and then
are transferred to the intestinal canal of food fishes. ^

A similar parasite of cyclops is Filaria medinensis?

The cladocera are generally quite free from parasites, but I have
found in several instances young nematoids in the blood sinus in
front of the heart in Daphnia schcejferi. These worms subsist
upon the nutriment m the blood which constantly bathes the
animal. True cysts could not be formed in the cobweb-like tis-
sues of the hosts. This is, so far as I can learn, the first publica-
tion of entozoa from cladocera, and the parasites are figured in
Plate T, Fig. 15. The animals were from 'Schimels Teich,' Leipzig.

While collecting copepods near Tuscaloosa, Ala., I gathered a
number of specimens of Cyclops teniiicornis, and nearly all were
unusually pale and feeble. On examination they proved to be in-
fested with a worm of the sub- order Distomeas. This sub-order
includes many distressing parasites and forms which are adapted
to be widely distributed by a long period of adolescence, and the
number of stages passed through before maturity is attained."

"The larvae live frequently in mollusca, and in maturity
inhabit the intestine of vertebrates.

Upon examination, the cyclops individuals collected were nearly

iClaus. Kleines Lehrbuch d. Zoologie, p. 368.

2Fedscheniio. Ueber d. liau. u. d. Entwicklung d. Filaria medinensis, Moscow.

10 TWELFTH ANNIJAL REPORT.

all found affected, some having as many as five parasites of various
sizes about the alimentary canal, in the common vascular cavity
which corresponds to the entire arterial and venous system of the
more highly organized Calanidse. The Cercerian or tailed stage
was not found. Were the life-history known it would probably
appear that the larval stage is passed within some young moUusks,
and that the adult infests some vertebrate, probably fish, and
would thus be perhaps transferred either in food or drink to
the human system.

It is worthy of notice that the host was soon destroyed by the
parasite, the post-imago or coronatus form being absent ; most
of the individuals thus infested possessed abnormally persistent
larval characters in antennae, etc." (See also below on Lagenella
mobilis).

The external parasites are more numerous but, in the main, less
dangerous. Among these are a variety of algge, and colonies of Vor-
ticellae and related animals. There is almost always a colony of
Acineta near the anus of Cyclops phaleratus. Rarely Stentor is
found upon the body of Cyclops.

The most remarkable ectoparasite among ihe protozoa is the
remarkable louse-like ciliate protozoan, to be described beyond,
found as a parasite of Diaptomus pallidus.

Finally, certain of the rotifera are very constant enemies of the
entomostraca, one species making its diet almost exclusively of
Chydorus sph^ericus and stowing them away Avith remarkable
facility with its forceps-like jaws.

A New Species of Corethra.
(Plate y. Figs. 1-4 )

The Corethra plumicornis as known in the larval form is one
of the most abundant of the inhabitants of our inland waters, and
its form and habits are sufficiently well known. (See Types of
Animal Life by the author for description and figures.)

A second, and presumably new, species was found in a night
gathering from Lake of the Isles near Minneapolis. In motion it
differed so entirely, though indescribably, that the eye recognized
it at once as new. The few specimens then obtained were all that
have been seen, but I will here give a brief description of the larva
and pupa in hope that the imago may finally be encountered.

STATE GEOLOGIST. 11

The form is more slender than in C. plumicornis. The tracheal
vessels are of a different form and color, and the viscera have ob-
vious differences. Most conspicuous variations, however, are seen
in the shape of the head, which is slender and attenuated toward
the insertion of the antennae. The antennae are shortish and have
a spine outwardly. The cuticular appendages have an unusual
form as has the labrum. The anterior part of the head is
spiny. The armature of the end of the abdomen is peculiar.

The posterior rudimentary appendages are of a different form,
and the claws are replaced by club-shaped bodies. A curious ap-
pendage below is indicated in the name. The pupa has an extra-
ordinarily elongate abdomen which terminates in two paddle-like
appendages loosely ciliated outwardly. This species may be called

Corethra appeucliculata, sp. n.

A New Ectoparasitic Protozoan.
(Plate V. Figs. 12-13.)

The very strange monocellular animal referred to was found scur-
rying over the body of Diaptomus pallidus in a manner like that
of a louse scrambling over a bare spot upon its host. The body is
disc-shaped and about .04 mm. in diameter. The lower or ciliated
side is flat and circular. The upper or aboral portion is convex
with an annular depression of greater or less regularity about half
way from the center to the margin. The lower side has a chitinous
barred ring, corresponding to the depression above, containing
about 25 radially arranged bars, each of which, apparently, forms
the support for a long ciliura which with the others forms a circlet
extending beyond the margin. These cilia are used as feet and by
them the animal is able to move in any direction, apparently with
none of the uncertainty of motion usual to ciliate infusoria. The
protoplasm is granular and contains one or more contractile vesicles,
one of which appeared very regularly in the center of the chitinous
ring before mentioned. These animals can also swim freely, but
after a short excursion usually came quickly back, and after
shuffling or sliding over the smooth surface of the crustacean as-
sumed a position of repose. The generic afl&nites of this protozoan

12 TWELFTH ANNUAL REPORT.

are uncertain (Chilodoutidse?); the specific name may, perhaps, be
safely applied as follows:

pedicularis, sp. n.

Cragin notices the occurrence in American species ot Cyclops of
Lagenella mobilis, Rehberg. This gregarine (?) was found by him
at Cambridge, inhabiting in large numbers the digestive tract of
species of Cyclops, and has since then been observed in Minnesota.

STATE GEOLOGIST. 13

CHAPTER II.

ORDER CLADOCEUA.

'This very extensive groap contains a variety of types, but there
are suflSciently evident connecting links uniting the extremes of
structure. The Gynmomera which, following the usual custom,
we include here, stand distinct from the other groups, yet have suf-
ficiently evident cladoceran affinities. It is very unfortunate for
setiological speculation thatsrthis the only truly marine group
should stand thus isolated from its fellows. Aecording to the no-
tions at present prevailing, the Phyllopods stand nearest the primi-
tive type of Crustacea. There are unmistakable hints at an early
origin for that group, and not less evident are certain analogies
with both Cladocera and Copepoda.

There has, however, recently been made an attempt to derive the
Phyllopods from an original cladoceran stem with, as we think,
somewhat unsatisfactory results. Do we not the rather see in both
groups two like phases which may be looked upon as incidental and
comparatively trivial. The shelled and the shell-less phasis appears
in both. The most closely shelled Phyllopod is unmistakably nearer
Branchipus even than any of the Cladocera. It would seem that
the brief and imperfect embryonic nauplius condition of the latter
sufficiently indicated their later origin. Again no fanciful analogy
can unite the Ostracoda with the Lynceidae. We know of no
recent discoveries casting discredit on the remark of Balfour: "the
independent origin of the Ostracoda from the main crustacean
stem seems probable."

Prof, Packard says:^

"We imagine that when a permanent body of fresh water became
established, as, for example, in perhaps early Silurian times, the
marine forms carried into it in the egg-condition, possibly by birds

i"A Monograph of the Phyllopod Crustacea," etc., Xllth Annual Rep. U. iS. Geol,
and Geog. ISurv. Terr.

14 TWELFTH ANNUAL REPORT.

[sic?] or by high winds, hatched young, which under favorable con-
ditions, changed into Sida, Moina, and Daphnia-like forms. The
Cladocera are, then, probably the more generalized forms, from
which the Phyllopods, at this time and probably ever since Devo-
nian times, i^cif excellence a fresh-water assemblage of forms, took
their origin," Whatever affinity there may be between the shelled
Phyllopods and the Cladocera, it would seem that the evidence is
conclusive that the latter group is not the direct continuation
of the line of development inaugurated by an ostracode ancestor.
As shown beyond, the present centre of the group seems near Moina
with indications of a divergence from this rather generalized type,
especially of degradation and heteronomy on the side of the
Lynceids.

It seems at the present time that more might be accomplished
for aetiology by a careful study of such groups as the present, in
which are a variety of closely allied forms than by the attempt to
join widely separated groups. When we shall have siezed upon
the latest eddies and mapped their dilfection, it may become possible
to combine the indications in such a way that lines of divergence
thus traced accurately through some small part of their course
may be produced backward to their intersection. This then is
our present duty — the accurate mapping of minute districts and the
careful noting of any moving straws, competent to indicate move-
ments in the vast complex of vitalized nature. We conceive the
cladocera to have had a comparatively recent origin, and to express
the culmination and retrograde development of a plan of structure
first differentiated after the appearance of clear bodies of fresh
water. All the species save a very few are confined to inland
waters. Accepting the above mentioned theory, the Sididas will
occupy the first place as departing least from the type from which
the whole group sprang, while it is connected by the genus
Daphnella with the Daphnidas. The Daphnidas, beginning with
Moina, find their ultimate development in some monstrous forms
of the genus Daphnia, but pass into the Lyncodaphnidae by way
of Macrothrix. The links uniting all these minor groups are very
obvious.

Our own ideas of the relationships among the Calytomerous
Cladocera are expressed in the accompanying table. This table is
to be considered a projection of a portion of a genealogical tree,
seen from below, in which the genus Moina forms the arbitrarily
chosen fixed point. The heavy dotted line is imagined as directed
downward vertically. That branch rising toward the top of the

STATE GEOLOGIST.

15

page is growing obliquely upward. The Daphnidge are represented
as expanding upon the same plane as Moiua, and the Lyncodaph-
nidce extend diagonally downward, producing the Lynceid branch
The Bosminidffi spring from the stem at a lower point. These
relations are made obvious by the figure giving a view of the ideal
tree as seen from the side.*

Umaosida

Sohpedidss

^-SJda.

PseudoSida

• ^ .— *"

,DaphnelLa

,Latona

(?;

<SID'ID/€>

I
I
r

Bosmlaa.

~~ MOINA Ceriodaphnia

<lyncodAphnid/e>

Streblocercus f^acrothrif v^

Simo^ephalus
/ "Daphnist

^ Scapho/e hen's

I

iV

Lyncodaphnia
I
I

LathoiiMra

Drepanothri/ ^ v-' —

> "x

I

I

- /liocryptUS

SIDIB>E L^

Acantholeberis ^ClYNCEID/E) \

_ Eurycercus ^^ '^'^
Camptocercus y y^

Alonopsis''

^

lAlona) y
Lynceus

{ F/eOroxusIs,

Graptolebris

Chydorus

"* Morwspilus

fig. 1. — table illustrating the relations of the
Cladocera Calyptomera.

*NOTE.— To adapt the diagram to the theory that the Lynceidse are the progenitors
of Cladocera, it is only necessary to revolve the imaginary lino to the right, till It
coincides with the axis of that family. The question mark may be understood to
indicate that the source of the pivotal group, Moina, is uncertain. The author must
confess that his inclination is toward a belief that the line culmin^vting in the Daph-
nidae diverged from a group of organisms resembling Phyllopoda, more definitely,
resembling Limnetes. There is a very remarkable resemblance between the larva
of Limnetes and Bosmina. The lateral spines of the former are, as will be shown
true homologues of the antennules of Bosmina. The later origin of the Phyllopoda
iu their present form may be well admitted

1 Entomostraca, sen Tnsecta testacea, quae in aquis Danise et Norwegise reperit
dcscripsit, etc. Otho Friedric Mueller, 1785.

2 Mouoc. qui se trouvent aux Envir. de Geneve.

16 TWELFTH ANNUAL REPORT.

The Cladocera or Daphnoidea are characterized by the more or
less leaf-like feet, and the lamina of thin chitine which encloses the
greater part of the body, or at least forms a sac for the protection
of the eggs. This so-called shell springs as a fold from the maxil-
lary segment and is the most conspicuous and variously formed,
while really least important, of the structural peculiarities.

All Cladocera begin life with a single median eye, but some lose
it during later life. In one case it remains the only visual organ.

The outer covering is in most cases changed by frequent moults.
The period of the moult is one of the most precarious in the life
history of the animal.

Although figures and brief descriptions of animals belonging to
this group are to be found in the works of Swammerdam, Leewen-
hoek, Trembley and other of the older authors, Mueller^ was the
first to produce a systematic work upon these in common with
other minute fresh- water Crustacea. He may be called the father
of the study of micro-crustacea. Jurine,- an eminent Swiss natur-
alist, was the next to contribute important discoveries relating to
these interesting animals, though Ramdohr had given anatomical
details of several species. Gruisthuisen, a little later gives farther
details of Daphnia sima (Simocephalus). The work of Milne
Edwards gives a resume of what was known regarding these ani-
mals in that period. Soon afterwards the work of Baird became
the beginning of a new era, and the study of the minute Crustacea
sprang into importance at once. The Scandinavian peninsula
being the birth-place of the science, it is proper that the most
exhaustive work on the group should be performed there.

The most important of the later writers are Leydig, Schoedler,
Fischer, Lilljeborg, P. E. Mueller, Sars, Weismann, Claus and
Kurz.

The complete bibliography of the subject up to Mueller's time is
found in Baird's British Entomostraca; the greater part of the
later bibliography is to be found in P. E. Mueller's Danmark's
Cladocera. A few only of the more important works are here
mentioned.

Koch, C. L., Deutchlands Crustaceen, etc.

Schoedler, J. E., Ueber Acanthocercus rigldus, etc.

Dana, J. £>., Crustacea of the Wilkes' Exploring Expedition.

Lievin, Die Branclilopoden der Danziger-Gegend.

Fischer, Leb., Ueber die in der Umgegend von St. Petersburg vorkommenden Crus-
taceen, etc., 1851.

Lilljeborg, W., De Crustaceis ex ordinibus tribus, (or) Cm de inom Skane forekom-
niande Crustaceer af ordningarne Cladocera, Ostracoda ocb Cope-
poda.

STATE GEOLOGIST. 17

This valua'le work is particularly good on the Cladocera, but is

unfortunately vdthout Latin descriptions; so that the Swedish

text is a hindrance to its usefulness. It is chiefly of historic value

now. Large 8vo; Lund, 1855.

Schoedler, J. E., Die Branchipoden der Umgegend von Berlin, 1858.

Smitt, F. A., Sur les Ephlppes des Daphnes.

Lubbock, J., An account of the two methods of reproduction in Daphnia, etc.

Leyclig, Fr., Naturgeschichte der Daphniden.

The most magnificent work published.

lAlljeborg, W., Leptodora hyalina, 1861.

Sars, G. O., Om Crustacea Cladocera, iagttagne 1 Omegnen af Christlania, 1862.

This valuable work is difficult of access, printed on thin paper and

without illustrations. A second paper by the same author in 1863

is mentioned, but I have never seen it.

Sehoedlcr, J. E., Neue Beitrage zur Naturgeschicte der Cladoceren, 1863.

One of the most important works on the Lynceidae. The author

is rather too credulous and inclined to form new species.

Klunzinger, Einiges zur Anatomic der Daphniden nebst kurzen Bemerkungen ueher

die Susswasserfauna der Umgegend Cairo's.
Sars, G. O., Norges Ferskvandskrebsdyr Cladocera ctenopoda, 1865.

The best work on the Sididfe, etc.

Mueller, P. E., Danmark's Cladocera.

One of the most useful books on the subject. Especially good

on Lynceidffi and Bosminidae.

Plateau, Felix, Recherches sur les Crustaces d'eau douce, etc., 1867-69.
Mueller, P. E., Note sur les Cladoceres des Grands Lacs de la Suisse.
Wcismann, A., Bau und I^benserschelnungen Leptodora hyalina.
Sars, G. O., Cm en dimorph Udvikllng Samt Generationsvexel hos Leptodora, 1873.
Clau^, C, Zur kennt. d Organ, u. d. felneren Baues der Daphniden.
Vlaus, C, Zur kennt. des Baues, etc., der Polyphemiden.

Gruher and Weismann, Ueber elnige neue Oder unvollkomen gekannte Daphniden.
Welsmanyi, Thierleben im Bodensee, 1877.

Liutz, A., Untersuchungen ueber Cladoceren der umgebung von Bern.
Claus, C, Die Schalendruse der Daphniden, 1874.
Spangenbery, Fr., Ueber Bau und Entwicklung der Daphniden.
lAUjeborg, W., Crust. Suececorum Ordin. Branchiop. et Subord. Phyllop., 1877.
Pavesi, P., Nuova Serei di recherche della fauna pelagica nei laghi Italiani, 1877-1879.
Grobben, C, Zur Entwicklungsgeschicte d. Moina rectirostris, 1789.
Wcismann, Beitrage zur Naturgsch. der Daphnoiden, Leipzig, 1876-79. (Valuable on
the physiology).

The American literature may be catalogued in a few lines. The
first descriptions and figures with which I am familiar are those in
the Rep. of the U. S. Fish Commission, 1874, where S, L Smith notes
Daphnia galeata, D. pellucida and D. pulex; also a species of Bos-
mina, Eurycercus lamellatus and Leptodora hyalina.

A. E. Birge was the first to systematically study Cladocera in

America, and his " Notes on Cladocera " furnished a basis upon

2

M

18 TWELFTH ANNUAL KEPORT.

which to build. A few notes were published by the writer a little
later.

A few additional notes and descriptions of new species were
published in the eleventh annual report of the Minnesota geol.
and nat. hist, survey.

Prof. Birge published other notes in the Medical Journal and
Examiner of Chicago, which I have not seen.

Prof. Forbes of Normal, 111., in an article in the American
Naturalist., July, 1882, adds a number of facts and one new species.

In addition to the above, a figure of Sida was printed in one
of Hayden's Survey Reports, and some account of the Cladocera
of lake Michigan was given by B. W. Thomas, I believe, in one of
the official reports of the Chicago Water Commission.

CLASSIFICATION OF THE CLADOCERA.

SUB-ORDER I — CALYPTOMERA (membrane-clothed).

Body enclosed in a bivalve shell. Mandibles truncate below. Maxillae distinct,
spiny. Thoracic ganglia discrete.

Tribe I. — Ctenopoda.

Feet six, similar, foliaceous, all distinctly branchiate.

Fam. 1.— Sidide.

Swimming antennas with two unequal rami, intestine simple.

Fam. 2. — Holopedid^.

Swimming antennae simple, elongate cylindrical (in the male prehensile),
intestine with two lateral dilations.

Tkibe II. — Anomopoda.

Peet five (or six) pairs, the anterior pair more or less prehensile and destitute
of branchiae.

Fam. 1. — Daphnid^.

Rami of antennaj three and four-jointed, five pairs of feet, the last with
a curved appendage guarding branchial sac; antenuules of female
short, one-]ointed.

Fam. 2. — Bosminid^.

six pairs of feet, antennules elongated, many-jointed.

Fam. 3. — Lyncodaphnid^.

Antenuules of female elongated, but one-jointed; intestine simple or
convolute.

Fam. 4.— Lynceid^.

Antennae with both rami three-jointed, intestine convolute, with ab-
dominal but no anterior cseca.

SUB-ORDER II.— GYMNOMERA (destitute of covering).

Body without or nearly destitute of bivalve shell ; feet not branchiate, spiny. An-
terior thoracic ganglia In one mass.

STATE GEOLOGIST. 19

FaM. 1. — POLYPHEMID^.

Abdomen curved, terminating in two long stylets.

Fam. 2. — Leptodoridje.

Abdomen straight, ending in short claws.

FAMILY SIDIDiE.

Head separated from the body by a depression, without promin-
ent fornices (or spreading shields) over the base of the antennae.
First pair of antenna, or antennules, as we shall uniformly call
them, one-jointed, usually rather small in the female, but extend-
ing into a very strong flagellum in the male. Antennas long,
biramose, with unequal branches. Mandibles truncate at the end.
Maxillae armed with large spines. The form is usually elongate,
and the abdomen often extends beyond the edge of the shell
behind. The male openings are usually in the end of long ap-
pendages which depend from the base of the post-abdomen. This
interesting family is represented in America so far by four species,
one of which constitutes a new genus. Others will undoubtedly
be found upon a careful study of the fauna of the great lakes
Most of the species prefer the clearer and colder water of large
lakes. The processes of development, as traced by the writer, vary
very little from the method exhibited by Moina. The ephippial
condition, however, is not found in these animals which are less
subject to destructive influences of the climate. They do, how-
ever, produce so-called winter eggs which are laid in October and
are distinguished from the summer eggs, which hatch in the brood
cavity, by a brown color and the presence of fatty spheres. These
eggs are produced in large numbers in distinction from most other
Cladocera in which the winter eggs are very few. These eggs are
permitted to settle to the bottom and there develop at the proper
time. Sida crystallina is often found in immense numbers in large
lakes which contain abundant plant growth. The size, and especi-
ally the reproduction activity, is very dependent on the environ-
ment, and hence little success is obtained in preservation in
aquaria. Some of the genera are nocturnal and should be sought
at the surface on quiet evenings.

I. — Genus Sida. Straus.
(Plate N. Figs. 12-14.)

Body elongate, hyaline. Head small, quadrate. Fornices ab-
sent. Antennules of female small, truncate; of male, with a long

20 TWELFTH ANNUAL REPORT.

flagellum. Second antennEe with the rami two and three-jointed,

Male with the sexual openings just behind the last pair of feet.

It is the upper or longer branch of the antennae which in Sida is

three-jointed, while the reverse is the case in the next genus.

The only species, according to P, E. Mueller, is the ubiquitous S.

crystallina. The S. elongata of Sars is distinguished by the

smaller head and its concave lower margin and more elongate

shell. The terminal joint of the longer ramus has one less seta

than S. crystallina, while the post-abdomen has more numerous

spines. We incline to believe it a valid variety at least. The

bibliography below is extracted from a previous report:
Daphne crystallina, Mueller.
Daphnia crystallina, Latreille, Bosc.
Sida crystallina, Straus, Mem. Mus. Hist. Nat.
Sida crystallina, M. Edwards, Hist. Nat. Crust.
Monoculus crystallinus, Gmelin, Manuel. Fabricius.
Monoculus elongatus, De Geer, Mem. servir. Hist. Ins.
Sida crystallina, Lievin, Branch, d. Danziger Geg.

Baird, Brit. Entom.

LiLLjEBOBG, De crust, ex ord. trib.

Fischer.

SCHOEDLER, Die Braucb. d. Umg. v. Berlin.
Neue. Beitr.

Leydig, Naturg. d. Daph.

Sars, Norges Ferskv— Krebsdyr.
Sida elongata, Sars, " " "

Sida crystallina, P. E. Mueller, Danmark's Cladocera.

KuRz, Dodekas Neuer Cladoceren.

BiRGE, Notes on Cladocera.

Herrick, Mlcrosc, Entom.

LuTz, Untersuch, u. d. Cladoceren d. Umg. v. Bern., 1878.

Weismann,

Grobben, Entwicklung. Moina.

Herrick, Crustacea of Minnesota.

II. — Genus Pseudo-sida. Herrick. (Genus n.)

Similar to Sida, Antennules of the female, with a long flagel-
lum, like that of the male of Sida, sensory setse lateral. Body
elongate, head short, extending into a sharp beak. The post-
abdomen is armed with groups of sharp spines or bristles. Most
characteristic, however, is the fact that the antennary joint, which
in Sida is two-jointed, in this species is tri-articulate, and the two-
jointed ramus has a great number of satse (16-17).

Sp. 1. Pseudo-sida bidentata, Herrick. (Sp. n.)

(Plate K. Fig. 9.)
Post-abdomen armed with 12-14 clusters of spinules in a trans-
verse row ; the terminal claw armed with two long basal spines,
and with numbers of fine teeth on the inside. The two-jointed

STATE GEOLOGIST. 21

ramus of the antennas has six setae on the basal, and ten or eleven
on the terminal joint, while the three-jointed ramus has a short
terminal joint bernng three spines. The valves are marked with
sparse spines on the lower margin. In most respects this species
is like Sida, which it resembles in size. In the form of the female
antenna it is like Latona which it also somewhat resembles'in the
number of joints of the antennas and the numerous setae they bear.
It is certainly an interesting transition form. Found only in
swamps bordering Mobile bay, Ala., but whether in brackish or
fresh water my notes do not inform me. Sida crystallina lives far
out in the bay, and Daphnella is found in pools along shore.

III. — Genus Limnosida. Sars.

(Plate N. Fig. 9.)

Head crested; eye in a conical prominence. Shell elongated,
produced above in an acute angle. Antennules small, truncate in
the female; in the male of enormous size; antennas very long.
Post-abdomen smooth; terminal claw spiny.

The one species, L. frontosa, Sars, is not yet known in America.

IV. — Genus Daphnella. Baird.

Neither beak nor fornices present. Antennules of female small,
truncate ; those of male long, flagellate. Antennte with two-and
three-jointed rami. Male with a hook on the first foot, and large
oopulatory organs attached to the base of the post-abdomen.

Sp. 1. Daphnella brachyura, Lievin.

^ida hrachyura, Lievin, Branch, d Danziger Geg.

Daphnella wingii, Baird, Brit. Entom.

Sida hrachyura, Lilljbbokg, De crust, ex ord. trib.

Diaphanosoma brandtianum. Fischer. Erganzig. Berichtig.

Daphnella brandtiana, Saks, Norges Ferskv.— Krebsdyr.

Daphnella hrachyura, P. E. Mueller, Danmark'sCladocera.

Daphnella hrachyura, Lutz, Untersuchung u. die Ciadoceren d. Umg. v. Bern.

Sida hrachyura, Pavesti, Nuova serie di recerche della fauna pelagica nei laghi

Itaiiani (L. Trasimene).
Daphnella hrachyura, Hekeick, Notes on Crustacea of Minnesota.
(Compare also D. expinosa, Bikge, Notes on Cladocera p. 3.)

The species of Daphnella found about Minneapolis, occasionally
abundant, seems not to differ in any important character from
European types of D. hrachyura, although I formerly regarded it
as distinct (D. winchelli. Microscopic Entom,, Addenda).

Head less than i the body (about .27 mm., while the body is
-.6 mm. long); eye about i head; antennas when reflexed extend a
little beyond f the length of body. Male, .7 mm. long; antennas

22 TWELFTH ANNUAL REPORT.

reflexed, reaching base of shell ; anterior antenme extremely long;
copulating organs reaching nearly to end of claws. Having care-
fully compared our specimens with the descriptions and figures
given by Birge for his D. expinosa, the evidence seems to indicate
not only that they are identical, but both are really D. brachyura»
The distinctive characters of D. expinosa are a greater indentation
between head and body, absence of caudal teeth, greater length of
male appendages, and the opening of the t^asa deferentia below the
" instep " of these appendages.

The absence of teeth upon the post-abdomen is of even generic
importance according to Sars, who gives it in his synopsis of
genera as typical for Daphnella, In our specimens the claws are
at least pectinate if not serrate, while the appendages of the male
reach generally nearly to the middle of the claws. The relative
length of these appendages and the antennae of the male is variable.

Sp. 2. Daphnella brandtiana, Fischer.

Head as long as half the body, antennae when reflexed reaching
beyond the posterior margin of the valves. Length 0.8 mm. Of
the validity of this species we can form no conclusion. It is
usually considered a variety or phase of the above.

V. — Genus Latona, Straus.
(Plate K. Fig. 8.)

Body elongate, broad; head large and square, appendaged below
with triangular laminae ; fornices present. Antenuules rather
large. The larger ramus of the antennae is two-jointed and has an
expanded process at the base. The lower posterior angle of the
shell has a peculiar diverging set of setge. The shell is often orna-
mented with numerous flecks of bright color. There is a copula-
tory apparatus in the male.

Latona setifera, Mueller,

Is the only species, and is not yet recognized in Minnesota, but
was found by Prof. Birge in lake Michigan.

FAMILY HOLOPEDID^.

Genus Holopedium, Zaddach.
(Plate N. Fig. 11.)

The peculiar animal bearing the name Holopedium gibberum
has the brood cavity greatly elevated, and the whole upper part of

STATE GEOLOGIST. 23

the auitnal is covered by a jelly-like mass secreted as a protection
or float. The antennas are simple in the female and extend
through a slit in this covering. In the male they are prehensile
and have rudimentary inner rami. It would be difiicult to recog-
nize the affinity of the female with its monstrous form were it not
for the male and particularly the development history. Found in
this state probably only in lake Superior. Forbes mentions it from
lake Michigan.

'o"-

FAMILY DAPHNID^.

The family Daphnidse contains the genera Moina, Ceriodaphnia,
Scapholeberis, Simocephalns and Daphnia, which include tiie com-
monest, as well as some of the largest, Cladocera. The genera may
be distinguished by the following table:

I. Head rounded, not beaked; antennules long in both sexes, shell

not covering the end of the abdomen Moina.

II. Head rounded ; antennules rather short ; shell enclosing whole

body Ceriodaphnia.

III. Head somewhat beaked below, shell angled below or extending

in long spines from the lower angle, pigmentfleck roundish.. .Scapholeberis.

IV. Head beaked below ; shell rounded below, with a blunt spine

above ; pigment fleck elongate Simoccphalus.

V. Head beaked below ; shell extending in a sharp spine at the upper

posterior angle ; pigment fleck small Daphnia.

The Circulatory System of the Daphnid.?:.

In the Daphnidce, and, indeed, the Cladocera in general, we meet
an instance of great development of surfaces at the expense of
solidity of form and compactness of organs. The whole body is
composed of an aggregate of laminae, and the appendages all ap-
proximate more or less toward this fundamental modification.
Thus, for example, the head is a leaf-like body with a laminate shield
above and a pair of flat organs beneath. The abdomen terminates in
a knife-like post-abdomen, while the thorax, with its narrow form,
foliaceous feet and, far more, the enormous development of the
outer wall to enclose, more or less fully, the entire body, is the
typical illustration of this fact. Necessarily this structural modi-
fication exerts a formative influence on the internal organs which
are all more or less influenced by it; and this is peculiarly the case
with the more external and, in general, the paired organs. Thus
the " shell glands," so called, which in Copepoda are generally
coiled tubes, become here greatly flattened organs closely united
with the shell. The physiological result of this modification is the

21 IWELFTH ANNUAL REPORT.

sensitiveness to changes in the environment, which is universal
among the Daphnidw. The compact Copepoda survive the vicissi-
tudes of confinement with comparative immuity, but the first taint
in the water destroys the delicate organism oi DapJmia. The cause
for this may be found in the exposure of the most vital and delicate
parts of the organism to the influences of the surrounding aqueous
medium. In particular the circulatory and respiratory systems,
which here are not easily to be distinguished one from the other,
constitute a relatively very large area of close contact with the
water. It thus happens that the central organs are influenced in
a very short time by whatever deleterious substances may be dis-
seminated in the water.

Notwithstanding this lack of centralization, the structure of
these animals is of a very considerable degree of complexity and,
presenting so many instructive modifications under circumstances
so favorable for study, has been verj' thoroughly investigated. The
very transparency which has made it possible to clear up many
questionable points in crustaceoloey from the lessons learned in
Daphnia, has rendered the investigation of certain sets of organs
extremely diflicult, and among these may be mentioned the circula-
tory system. The circulation of the nutritive fluid and the gen-
eral facts connected with the heart were indeed early understood;
but there remains many a detail and some important relations
which are as yet either imperfectly known or entirely misunder-
stood. The following notes are offered as a contribution to the, as
yet incomplete, knowledge of the circulatory apparatus.

The observations were confined for the most part to Daphnia
schcefferi and Simocephalus vetuliis, with occasional comparisons
with Eurycercus, Pleuroxis, Pasithea and others. It is greatly
to be desired that the studj'' might be carried to the Sididse,
in which the larger size and superior transparency would doubt-
less reward the search with several, as yet doubtful details.
The circulation of the nutritive fluid in the Daphnidse, then, is
somewhat complicated, but may be divided into a superficial and a
deep system. It must be remarked that this distinction is arbitrary
and only used for its convenience. The one extends over the entire
inner surface of the carapace, while the latter is in close relation
with the vegetative organs, and extends into the branchial vessels
of the feet. The nutritive fluid which is normally colorless and
supplied with corpuscles of organized nutriment, (it seems doubt-
ful if they should be called blood corpuscles) is confined for the
most, if not its entire, course within membranous walls of conuec-

STATE GEOLOGIST. 25

tive tissue which, however, instead of assuming a definite form as
*'biood vessels," for the most part conform to the contour furnished
by the firmer organs.

This membrane which is frequently folded upon itself and invests
the body walls and the inner organs, is in some places free, and may
be seen as a pulsating, swinging film, or, more frequently, it can
only be detected as a swaying line (seen in optical sections), thus
giving rise to the misapprehension that one is dealing with a thread,
or as moving graius, in which case the film is itself invisible but its
presence is indicated by the attached grains of protoplasm. About
the heart the free swaying portions of this membranous layer are
so numerous as to render it almost impossible to distinguish the
essential from the accidental appearances.

This membrane must serve the most various purposes; aside from
the mere retention and direction of the blood currents, it is often
transformed into a branchial surface. At definite points it becomes
the bearer of the cells which were above mentioned as grains of
protoplasm. These are most numerous in young and well-fed ani-
mals, and in particular in gravid females, while, on the contrary,
mature males and females after the escape of the young, are nearly
devoid of such bodies. These are most numerous in angles of the
membrane, particularly about the heart, shell glands, ovaries,
intestine and the branchial spaces in the feet.

These cells vary in size from that of the blood corpuscles to
larger cells with nuclei of comparatively very large size. It
would be too much to say that such cells are developing blood
corpuscles; but that they are reservoirs of nutriment which serve
to supply the increased demand upon the blood in exigencies of
the existence of the animal, cannot be doubted. It is a well known
fact that the number of blood corpuscles, so called, likewise varies,
and apparently under the same conditions. It seems altogether
probable that the two facts may be considered as supplementary,
i. e. that the same process of depauperating of the blood, which
deprives it of its corpuscles in an earlier stage, lays waste those
supplies laid up in the cells referred to (whether by their actual
separation as blood corpuscles or simply desolving of the contained
material is of little importance). These cells also are thus paralel-
lized with the " oil globules" of Copepoda. In such copepods as
Cyclops and Canthocdinptiis^ which appear to have no differen-
tiated heart, there are always present drops of colored fluid, which
are most numerous in well-fed and pregnant specimens. These

26 TWELFTH ANNUAL KEPORT.

drops occupy the same relative position as the blood globules of
other Crustacea, /. e., they lie within a very thin membrane cor-
responding to the vascular walls of other animals. This mem-
brane, in general, invests the alimentary canal, as can be very
readily seen in the abdomen, where it encloses a considerable space
about the intestine, which is filled with fluid, investing more or
less completely the muscles and other organs. As there is no
rapid circulation of blood, these "oil drops'' are comparatively
stationary, and yet are moved slowly by the constant contraction
of the walls of the alimentary canal which, in the anterior part, or
stomach, are thick and glandular, while in the abdomen they seem
to be more fitted for respiratory function.

The above arrangement in Cyclops is correlated with its com-
pact habit and thick carapace, and forms a simple starting-point
for the study of the circulatory system in arthropods. It seems
that the walls of the membranous blood cavity are themselves also^
in places, furnished with muscles, so that the fluid is not depend-
ent entirely on the vermiform or the peristaltic motions of the
intestine for its escape from stagnation. If this be correct, we
here have an indication of the origin of the central organ of the
circulatory system.

But to return to Daphnia, the heart lies in the dorsal region
over the intestine upon which it may be said to ride, as it were
astride, though as we shall see, it is separated from the intestine
by other organs. In Eurijcercus this is most evident, as here the
heart is more obviously bifurcate.

The heart and circulation in Daphnia has been described
more or less at length by many authors, in particular Glaus
(Zur Kenntniss der Daphniden und verwanter Cladoceren.
Zeitsch. f. Wiss. Zool. Bd. xxvii.) and Gruithuisen (the work
of this author I have not seen), while Weismann (Ueber Bau
und Lebenserscheinungen von Leptodora hyalina, 1874) describes
the heart of Leptodora, and Glaus (Zur Kenntniss des Baues und
der Organ, der Polyphemiden), that of the Polyphemidge. Other
authors, except G. 0. Sars, who elucidates some points in the
circulation of blood in Sida, seem to have added little or nothing
to our knowledge of this interesting subject.

As already often described, the heart occupies a place in a
definite space — the pericardial chamber — the summit of which is
the dorsal shield which, we believe, should 1 e distinguished from
the remainder of the so-called cephalic shield. (It is usual to
describe the shell of Daphnia as consisting of a bivalve posterior

STATR GEOLOGIST. 27

portion or ormosteg if e, and a simple anterior cephalostegite\ but it
seems much more proper to consider that portion of the shell
which covers the pericardial space, and is the point of attachment
of the powerful muscles of the abdomen and of the membranous
walls of the pericardium, as a distinct portion of the carapace, as it
often evidently appears through the presence of a distinct suture,
or, in its absence, through the peculiar sculpture of the shell. In
such case it might also be proper to distinguish two regions on the
lateral appendages of this dorsal shield, an upper and a lower,
separated by the more or less obvious line, extending from the
union of the lateral lines of the dorsal and cephalic shield in
nearly a straight line toward the posterior portion of the shell,
and indicating the insertion of the muscles which move the feet
and post-abdomen. The lateral walls of the pericardial space
are the shell-walls themselves, and the floor is formed by a mem-
brane supported on, and investing in part, the strong muscles
which connect the abdomen with the upper anterior part of the
dorsal plate. Thus a space is left between the pericardium and the
intestine which is occupied by a special blood sinus leading toward
the posterior and lower part of the abdomen. The posterior wall of
the space is formed by a chitinous partition which bounds the
brood space, or its homologue, and is connected by chitinous
processes (stutzbalken) with the outer skeleton. The anterior, on
the other hand, is only bounded by the supporting ligaments of
the abdomen above described and membranous partitions. As
usually described, the heart lies suspended in the cavity thus de-
fined, by slender muscular threads, more or less like those of the
heart of Corethra larvae and the like; and such seems to be the
case at first, but a more careful study shows that this is far from
correct. On the contrary, the chief supports of the heart are
membranes which, seen in cross-section with the attached grains
or blood globules, assume the appearance of exceedingly slender
structureless threads. The action of re-agents indicates that these
supposed threads are not muscles, but composed of connective
tissue; while by changing the focus the sharpness of the line is
frequently not altered, but its relative position is changed^ — a simple
test which often serves to dispel an illusion of this sort. That
there are some threads of the character above mentioned is not to
be doubted, as in connection with the valves of the heart; but the
proper support of the heart is found in the membranes which
invest it in part, and are reflected upon the walls of the shell and,
anteriorly, of the intestine. It is not yet possible to fully describe

28 TWELFTH ANNUAL REPORT.

the insertion of these tissues, as there is so large a number, especi-
ally about the anterior opening, where they lie in all directions
and at all angles, and are so transparent, that only their vertical
sections appear as dark lines. Thus the same membrane appears
and disappears, only to re-appear in a different position where it
might be readily taken for a distinct membrane. In general,
however, I hope to make no serious error in the following sum-
mary. Before going into detail, however, it will be necessary to
consider the intimate structure of the heart, as well as its general
shape and position.

The general shape is that of an irregular oval with the greatest
convexity posterior {Daphnia. etc.), or it may be strongly bifid and
thus somewhat Y-shaped (Eicrucercus, etc.). It is held in position
in the pericardial cavity by the membranes above alluded to, to
which it is attached at definite points, the principal of which are two
slight enlargements on the lower posterior portion, which are in part
opposed to each other and also to a superior posterior point of
insertion. All three of these points are thus held in relation with
the shell with which the attached membrane is connected on either
side below and above. The membrane then extends part way along
the heart wall towards the anterior and is then reflected to the
shell wall. The result of this is that the pericardial space is an
angular cavity opening in front. It would seem as though the
membrane attaching the heart were identical with that lining the
cavity itself. The heart proper is obviously composed of series of
muscular elements, which are considered as simple cells by Glaus,
and which in young individuals show very destinct nuclei of compar-
atively large size. These are arranged like the meridian lines of a
globe uniting above and below, thus forming the most effective
apparatus possible for contracting the heart. In the smaller
Daphnidse, as stated by Glaus, there seems to be but a single layer
of muscular rays, but in D. schsefferi and Siuiocephalus I have
repeatedly satisfied myself that some of the longitudinal rays
sink below the others and form a series of longitudinal muscles,
as stated by earlier writers. These are furnished with a nucleus
which is frequently more or less external, appearing like a spheri-
cal appendage. In Leptodora Weismann has shown the heart to
consist primarily of a membrane of connective tissue, upon which
the muscular fibres or cells sit in somewhat the same position as
in Daphnia, except that there is not the same regularity in the
arrangement. There are many considerations which would lead
us to expect the same structure in Daphnia, though it is not yet

STATE GEOLOGIST. 29

demonstrated; and the structure of the anterior opening seems to
point in the same direction. At any rate there is a close connec-
tion between the muscular and connective parts of the heart. We
have, then, in the heart of Daphnia a highly developed apparatus
for closing it, but apparently none for its opening. This certainly
is not accomplished by the few fibers which connect the heart
with the shell, the very contractility of which is doubtful.
Nay, more, these are insufficient even to hold it in its place in the
cavity. Still less can we assume that the heart, from any inherent
power, can open itself. This must be explained by the operation
of two factors which are interdependent, i. e., the elasticity of the
supporting membranes and the unequal pressure of the blood in
different parts of the bcdy. 1. The membranes which support
the heart are attached not at right angles, but, on the contrary, in
a direction more nearly parallel to the walls of the heart, and thus
whatever elasticity they possess is greatly increased; and the
diminishing of the size of the heart draws these membranes out
of their position at the expense of their elasticity, which tends
to restore them to their original position when the pressure is
removed, in the same way a drum-head returns after a blow to its
normal position. This factor is, however, only operative so long
as the whole system of membranes to which these belong is dis-
tended with fluid. If this blood cavity be punctured, the fluid
flows out and the heart shrivels. It may continue to beat for
some time, but it will be seen that the eS'ort consists simply in
a vigorous contraction which is followed by no perceptible enlarge-
ment. 2, After the systole the blood of the heart is forced toward
the head, whence it is prevented from re-entering the pericardial
space directly by the valves and the membrane enclosing the
arterial blood. The pressure is therefore increased in all parts
of the system, except the pericardial chamber where it is greatly
diminished. The membranes supporting the heart are thus un-
usually tense, and the muscular efibrt having ceased, the walls of
the heart are distended, and blood flows in in the direction of the
least resistance through the two lateral openings or ventral valves
of the heart. The contraction of the heart during the systole is
not simultaneous in difi'erent parts, but begins by the contraction
of the posterior part where, being nearly free, the motion is more
marked. At the close of the systole the heart is irregularlj' con-
tracted, the points of attachment above described being more dis-
tended than the remaining portions. The anterior of the heart is
rendered very difficult to study by the fact that its opening is

30 TWELFTH ANKUAL REPORT.

covered by the muscles of the mandibles and obscured by the
many supporting and vibrating membranes alluded to.

It is, however, suspended by two folds of membrane which I have
been inclined at times to believe blood-vessels through appearances
resulting from the confused currents flowing about them. The
upper margin is also attached by a pair of cords directly to the
superior part of the shell. The anterior opening or arterial valve
is most perplexing, and the following description which applies
only to Daphnia schasfferi must be subject to some doubt. It ap-
pears however that it has been in a measure misunderstood by pre-
vious writers, and namely by Glaus, who compares it with that of
Leptodora, which if correctly described by Weismann, is not at all
identical in form, but quite comparable with one of the sides or lips
of the venous opening. It does not seem to be connected by a
thread, as stated for Leptodora^ with the aortal bulb, for in reality
there is no aortal bulb; the heart simply is connected with the
system of membranes which more or less inclose the system. The
floor of the so-called aortal space is a membrane which separates the
outflowing stream from a current which flows toward the abdomen
and passes directly under the arterial opening, so that it appears as
though there was a stream entering the heart from before as well
as at the sides; the arterial opening being nearer the dorsal part of
the heart than is naturally expected, and the slight enlargements
at the attachment of the supporting membrane favoring the im-
pression that there is here a veritable opening. The out-flowing
blood stream is bounded at first by the membrane above mentioned,
which is farther on reflexed onto the shell and intestine so that
the streams in the head flowing just under the shell are separated
from the deep dorsal stream flowing from the heart.* This main
current passes to the region of the eye between the horns of the
CEeca of the alimentary canal, and thence beneath the stomach, and
here divides, part becoming external and a deeper part passing un-
der the intestine, thence in front of the heart, flows into the deep
sinus which, as before said, passes beneath this organ. Other por-
tions of the returning stream flow around the angle of the union
of the head and body and constitute a stream just above the feet
in which the current flows vigorously.

Yet other portions flow into the region of the shell-gland and
are united with blood which here parses through the numerous
sinuses described by Glaus as surrounding this organ (Die Schalen-

*In Pasithea rectirostris this septum is easily seen as a swaying membrane, which near
the eye is reflexed to the top of the shell.

STATE GEOLOGIST. 31

druse der Daphuien) and thence flows into the abdomen, uniting
with the other two streams. A part also of the current in the head
flows into the antenua3 where it follows a deep course through the
basal joint in which the corpuscles may be seen to emerge to the
surface from two points where are spaces between the powerful
muscles, the first being near the base and the second near the ex-
tremity of this joint, and then to return and join the superficial
current.

The corpuscles appear to enter the rami very rarely if at all.
That part of the superficial stream which reaches the interior of
the pericardial chamber passes between the muscles of antennas
and jaws and seems to find its way into the greac current beneath
the heart, though I have also thought to have seen it fiow directly
into the pericardia] space as the lateral superficial streams do.
That part of the superficial stream which reaches the posterior
margin of the shell returns through a canal formed by the walls
■of the shell and the brood-space,between the"stutzbalken"of which
the blood corpuscles can be seen to glide more rapidly than in the
free lateral spaces.

Lastly,it only remains to follow the fortune of the strong stream
flowing along the neutral surface of the abdomen. The strong
current flowing beneath the heart enters a broad sinus Avhich lies
over the intestine and extends for over a third of its length, where
its walls unite with the surface of the intestine above and thus
open downward on either side.

The stream thus directed flows toward the openings of the base of
the feet. The structure of the branchiae has oot yet been clearly
•described. Instead of nearly spherical or oval chambers they
are really tubes which connect, on one hand with the opening
above, and below with the general cavity of the limb, whence the
blood returns to the abdomen. The current is very rapid through
these tubes. The blood having been returned to the ab-
domen, courses in the well known manner through the post-ab-
domen and flows over the intestine, thence over the back-flowing
stream to the posterior lower opening of the pericardial chamber.

The study of the actions of the heart is rendered more difficult
by the fact that in order to secure the greatest possible transpar-
ency, the living animal must be covered and a little pressure ap-
plied, which is frequently attended with abnormal variations of the
•circulation. In particular if the usual exit of the blood be stopped
by the c«ca of the intestine, as is frequently the case, the opera-
tion of the heart may be reversed, when a vigorous stream may be

32 TWELFTH ANNUAL REPOKT.

seen to enter the arterial opening and emerge from the ventricles.
This process would be impossible if the anterior valve were as de-
scribed by Claus and Weismann; while being really more like the
venous valves, it is easily and frequently permitted. The current
of the blood in this case stagnates except near the heart.

The rapidity of the pulsations of the heart varies with age and
condition of rest or motion.

In D. schaefferi this variauon may range from about 150 per
minute to perhaps 250, 200 being probably a fair t.verage. In a
young Simocephalus I have observed a heart beat 300 times in a
minute. Again, in a specimen of D. Schaefferi at rest the heart
was beating 170, but during the spasmodic motion of feet and an-
tennge the pulse rose to over 200.

I. — Genus Moina. Baird.

The systematic position of this genus has been the theme of
some discussion, it being claimed, with good reason, that there are
many resemblances to the Lyncodaphnidse (P. E. Mueller considers
it a transition to the Bosminidae and lyncodaphnids); on the other
hand, Leydig and Kurz regard it more closely allied to the Sididae^
with equally good reason. The long antennae, long narrow anten-
nules and many peculiarities in form, etc., suggest the macrothroid
crustaceans; the extended abdomen and especially the location of
the male seminal opening are like Daphnella, which Moina resem-
bles in motion and habit very strikingly. The absence of the pig-
ment fleck is no more a characteristic of the Sididae than of other
groups. After all has been said, the immediate affinities of the
genus are acknowledged to be with the Daphnidte.

The true place of the genus, as it appears to the writer, was
hinted at by Birge (Notes on Cladocera). Moina seems to be the
pivotal point of the Cladocera, at least of the families above men-
tioned. Without going into phylogenetic speculation, it is sug-
gestive that this genus can and does by preference live in very im-
pure water and may therefore have had an early origin. From
Moina diverges the stem of the Daphnidae by way of Ceriodaphnia,
Simocephalus and Daphnia. These two latter genera are intimately
connected by Simocephalus daphnoides, Herrick. Scapholeberis
is connected with Ceriodaphnia through S. angulata, Herrick.
The Sididffi seem to diverge by the way of Daphnella, through
which by means of Pseudo-sida the genus Sida is reached, and final-
ly Limnosida, Latona and Holopediura. The relationships of the
curious Polyphemidae are less evident.

STATE GEOLOGIST. 33

The Lyncoclaphnidas make an easy traasition to the Lynceids
proper, while the Bosminidae are still quite isolated, but are sug-
gested by Macrothrix pauper. The fact that Moina stands thus
related to radiating groups is simply suggestive, but it is sugges-
tive of its possible antiquity aud synthetic character.

The three species of this genus stand very poorly distinguished
from one another and their specific validity may be doubted.

The most exhaustive study of the embryology of the Cladocera
was based on Moina. [Grobben, Entivich d. Moina^ etc.)

The genus is characterized by Weismaun and Gruber^ about as
follows:

Head prone; separated by a depression from the thorax; fornices
obscure; rostrum none; pigment fleck absent; antennules of the
female large, moveable, furnished with a sensitive seta near the
middle, flagelliform; antennules of the male very large, hooked at
the end. The setaB of the antenna are all ciliate; the tri-articu-
late ramus with five setae; posterior margin of the valves thicker
in the median line; caudal setae very large, about twice in the
length of the animal; anus above the claws; feet of the first pair of
the male with a strong hook,

Weismann has shown that both summer and winter eggs origi-
nate from groups of four cells, one of which only is transformed
into the egg, the remaining three serving simply as a supply of
nourishment for the egg, which absorbs it directly. Both eggs and
nutrient cells develop from the epithelium of the termination of
the ovary. The summer eggs have less yolk than the winter brood,
and the yolk is bluish in the summer eggs and deep red in the
winter eggs of Moina rectirostris; while in M. paradoxa the sum-
mer eggs have yellow and the winter set snow-white yolk. There
are never more than two winter-eggs in any of the Daphnidae, but
there are as many as twenty summer eggs in some cases in Moiua.
In M, rectirostris only one winter egg is produced, which is one of
the best distinctions of the species, as this is, perhaps, the only case.
{Naturgeschichte der Daphnoideti, Weismann.) The first genera-
tion, springing from the winter eggs (impregnated eggs), is com-
posed solely of females which reproduce parthenogenetically; the
vsecond brood contains sexual males and females, thus completing
the cyclus. ^

1 Ueber einege neue oder unvolkommen gekannte Daphniden, Freiburg, 1877.
3

34 TWELFTH ANKDAL REPORT.

Sp. 1 . Moina rectirostris, Mueller.
(Plate A. Figs. 2, 5, 8, 10, 11.)

A. Var. vera.

Daphnia realiroslrU, O F- MOKLLER, Latreille, BOSC, Desmarest,SCHRA.Nk,Letdio.

Monoculas rcciiroslris, GMBLIN, FaBRICIUS, MANDEL; JURINE.

Pasilhea rectirostris, KoCH.

Moina rectiroflris, Baikd, WeismanN, Kurz, Birge.

li. Vur. bracliintiis.

Moiioculus brachialus. JORINE.

Dapania brrichiala, DESMARE3T, EDWARDS, Leydig.

Moina brac'iialn, Baird, WeISMANN.

C Both varieties.

Moina brachiala. P. E. MUHLLER. LilljeboRg,

The only tangible difference between the two forms thus united
is the fact that M. rectirostris produces but a single winter ovum
and hence has a one-chambered ephippium, while M. brachiata has
a two-chambered ephippium.

The head is separated Irom the thorax by a marked depression ; there
is a deep depression above the eye; the margins of the shell have few
bristles. The post-abdomen, which extends far beyond the edge of the
valves, bears about eleven hairy spines on either side, the lower
spine being two-cleft at the end; the base of the claws bears a
comb of small teeth, and the posterior margins are bristled. The
ephippium is oval; and the single cavity in M. rectirostris has
its longer axis horizontal, while the two cavities of M. brachiata are
vertical. The depression above the eye is deeper in the males, in
which sex also the antennae are longer and bent at the middle.
Tiie seminal bodies are stellate. Length 1, 2 mm. The ^orm is
.-subject to the greatest variation due to the varying number of sum-
mer eggs. Birge finds this species abundant. I have found both
this and the following species in various parts of the Mississippi
^yalley from Mobile to the upper river region.

Sp. 2.— Moina paracloxa, "Weismaun.

(Plate A. Figs. 1, 3, 6, 7, 9.)

The species differs in a few very insignificant points from the
previous one. The head is short and nearly evenly convex
above, with no deep depression above the eye; teeth of terminal
claws reduced to bristles which are only a little longer than the
series extending down the claw as in the above species; the first

l"Gruber and Weistnann, ueber einige neue oder unvollkmmen gekannte Daphniden
Freiburg, 1877

STATE GEOLOGIST. 35

foot of the male is furnished with a long bristle; the lower shell
margins are more bristly than in the previous forms; the ephip-
pium has two cavities, while the seminal bodies are crescent-shaped.

Sp. 3. — Moiiia iiiicrura, Ku

rz

This form may bn of specific value, but it is not sufficiently dis-
tinguished to make this certain. As described by Kurz, it seems to
be smaller (1 mm.) and most to resemble M. paradoxa, which was
not at that time described. The post-abdomen is short and has few
(6) spines, while the terminal claws are short and smooth; the
bead has a sinus above the eyes; the eyes are smaller, Avith numer-
ous lenses; the antennules are shorter (?) than in M. rectirostris;
the mandibles are partly exposed, while the shell margin overlying
is notched. Males and ephippial females were not observed. Not
distinguished in America.

II. — Genus Ceriodaphnia, Dana.

The geaus Cerioiiphnia is the successor to Moina, which some
species greatly resemble; the post-abdomen, however, is shorter
and has a habitus resembling Daphnia; the antennae are smaller,
and the shell is thick and coarsely reticulated.

CeriodapliQia has the same general mode of life as Moina, living
in muddy pools in late summer and bearing numerous broods
which often greatly extend the brood cavity. The antennules are
shorter but have a similar form; the male antennas show a transi-
tion in the various species from forms adapted for prehension to
such as are found in Daphnia. The brood cavity is closed by two
ridges on the abdomen instead of one, as in Moina, or three, as in
Daphnia.

The ephippium cjntains but a single ovum. In general, the
form is oval or quadrate, angled but not spined posteriorly; head
separated from the body by a deep depression; pigment fleck pres-
ent; beak absent; antennules moveable, rather short; antenna? with
the three- jointed ramus with five setee; first foot of the male with
•a hook or flagellum.

The members of this genus are danger signals from a hygienic
point of vievv, for they frequent water containing decaying matter;
as many as 1,400 were counted in a single quart of such water.
The genus is particularly perplexing, as the varieties named seem
to be hardly entitled to specific rank and are so similar as to re-
quire great care to properly distinguish.

36 TAVELFTH ANNUAL REPORT.

The following artificial key, it is believed, will assist in placing^
the specimens which may be obtained in America. There seem&
no reason to doubt that our fauna is very similar to that of north
Europe. Of the twelve species here enumerated at least one-third
may be synomyms and others of the remainder are with difficulty
distinguished.

Artificial Key to the Genus Ceriodaphnia.
A. Shell irregularly striate.

1. C. tnegops, Sai'S.

2. C. crisiata, Blrge.

Shell with hexagonal meshes.

a. Shell with doubly contoured markings.

(aa) Head broad, short.
8. C. pulchella, Sars.
(bb) Head narrowed, depressed.

4. C. rotunda, Straus, (antennules normal.)

5. C. ataftamensis, Herrick, (antennules elongate.)

b. Shell simply marked.

(cc) Claws witli teeth.

6. C. reticulata, Jurine.
[7]. C. dentata, Birge.

(dd) Claws without teeth.

I. Antennoe very long.

8. C. punctata, P. E. Mueller.

II. Antennte normal or short.
* Post-abdomen broad.

9. C. laticaudatus, P. E. Mueller. 1 mm. long.
[lOJ. C consors, Birge. 0.5 mm. long.

** Post-abdomen narrow.

t Head not angled behind the eye.

11. C. quadrangula, Mueller.

+t Head abruptly angled behind the eye.

12. C. scitula, Herriek.

C. Shell reticulate with rectangular meshes.

13. C. nitida, Schoedler.
[14]. C. texlilis, Dana.

Sp. 1. Ceriodaphuia meg^ops, Sars.
(Plate A. Figs. 16, 20.)

Cerioiaphnia megops, SARS, P. E. Mueller, Kurz. (The earlier synonymy;isidoubtful
See note, page 26, Schoedler's Neue Beitrage zur Naturgeschichte
der Cladoceren.

STATE GEOLOGIST. 37

This species is one of the largest and most readil}' distinguished
as well as rarest of the genus. Very characteristic is the fine an-
astomosing striation which breaks up into reticulation only near
the shell margins. This species seem^ to form the transition
toward Simocephalus with Scapholeberis, which, however,
diverges aloug its own peculiar track. The length is sometimes 1
mm. The head is obscurely angulated in front of the antennules,
which are large. The antennules of the male are long
and have a hooked setae at the end.

Typical C. megops has not yet been found in America, but the
following form takes its place.

Sp. 2 Ceriodaphuia cristata, Birge.

The description given by Birge would apply in almost every par-
ticular to C. megops, though he seemed to overlook the close con-
formity. The size is much less (0.7 mm.), and the post-abdomen
«eems more abruptly truncate; moreover the number of anal spines
is less. The crest upon the dorsal margin may be the effect of
prominences such as are described by P. E. Mueller; at auy rate, in
view of the fact that but few specimens were discovered, the sug-
gestion lies near that C. cristata is the young or, at least, a reduced
form of C. megops.

Found at Southampton, Mass.

Sp 3. —Ceriodaphuia pulchella, Sirs.

(Plate A, Figs. 14, 19.)
Ceriodaphnia pulchella, a x'RS, P. E. Mueller, Kubz.

Very much like C. reticulata, but smaller. Head large, turgid,
and angled in front of the antennules, forming almost a right an-
gle; fornices moderate; antennules rather large; shell oval, reticu-
lated with double contour lines; post-abdomen of medium size,
narrowed toward the end, slightly truncate, with about nine spines;
terminal claws short, smooth. The flagellum of the male antenna3
is but slightly hooked,0.5 — 0.6 mm. long. This species is not cer-
tainly identified from America, though a form with smooth claws
and small fornices occurs with C. dentata in some places.

Sp. 4. Ceriodaphuia rotunda, Straus.
(Plate B. Fig. 1. Plate A. Figs. 13 and 23.)

Daphnia rotunda, STRAUS, Baihd.

Ceriodaphnia rotunda. SCHOEDLER, SABS, P. E. MCKLLER, KURZ.

38 TWELFTH ANNUAL REPORT.

As said by Kurz, this species is not easily mistaken; the small
head (only paralleled by the following), the very evident reticula-
tions and the broad abdomen give it a peculiar habitus which i'^
unmistakable.

Head depressed, small, spiny below, not a:.gulated; fornices
prominent, thorned; body rotund, almost spined above; shell doubly
reticulate; post-abdomen broad, with seven or eight anal spines;
claws large, smooth. The male antennules are little larger than
those of the female. I have not yet seen this species in America.

Sp. 5. Cei iodaphnia alabainensis, Henick,

(Plate B. Ficr. 2.)
(American Naturalist, May 1883. Plate v, Figs. 11, 12.)

This species was seen but once and is insufficiently known. The-
body is elongate, quadrate, the shell reticulated with double con-
tour lines,the bead very small and produced downward below the eye^
which is very small, the antennules are longer than in any other
species, obviously two-jointed, with a lateral seta; the antennasr
are very long; post-abdomen long and rather narrow, with the
margins nearly parallel, truncate at the end, with over nine anal
spines; claws smooth, abruptly truncate. My drawing represents a
daphnia-like set of processes for closing the brood cavity. Length
1 mm. (?)

Tuscaloosa, Ala.

Sp. (> Ceriodapliiiia reticulata, J urine.

Monoculus reiiculatus, .JUBINE.

Daphnia reticulata, Baird, Leydig.

Ceriodaphnia quadrangula, SCHOEDLER.

Ceriodaphnia reticidata, Sars, P. E. MUELLER, KuRZ, Herrick.

Head long, obscurely angled in front of the antennules; fornices
very prominent; antennules small; post-abdomen of moderate size,
rounded at the end, slightly tapering; about eight long anal teeth:
terminal claws with a series of sharp spines at the base. The re-
ticulations are sharp but simple. The flagellum of the male an-
tennule is either straight or moderately curved. Kurz says that
some varieties have the fornices blunt while others are sharp. I
have seen only the blunt form which is then much like the next.

Sp. 7. Ceriodaphnia dentata, Birge.

This form differs from the above only in having the inside of the
claws fringed with minute bristles (sometimes absent), the angle

STATE GEOLOGIST. 39

of the head being more marked aad the foruices less prominent. It
is difficult to say whether our Minnesota specimens most resemble
this or the typical C. reticulata of Europe. They seem intermedi-
ate, some having foruices with an abrupt angle. It ma}' be in-
structive to quote Kurz on the European C. reticulata — "Examples
occur 0.8-0.9 mm. long, others on the contrary only 0.5-0.6 mm.
long and combining with the smaller size some differential char-
acters. In the larger variety I found the fornix obtuse, while in
the smaller it extends in a sharp thorn directed upward and out-
ward. In this small sub-species the secondary teeth of the claws
of the post-abdomen seemed to be absent, though in C. reticulata
3-5 are constantly present."

Sp. 8. Ceriodaphnia punctata, P. E. Mueller.
(Plate A. Figs. 1-3.)

Head depressed, rounded at the end, not angulated, ornamented
with minute spines within the hexagonal areas. Foruices slightly
prominent, either smooth or spiny; antennules very long; shell
rotund, reticulated; post-abdomen of medium size, width nearly
uniform, truncate below at an obtuse angle; anal spines large, in-
creasing toward the end; claws smooth. Length 0.7 — 0.9 mm.

Found as yet only in Scandinavia.

Sp. 9. Ceriodapliuia laticaudata, P. E. Mueller.
(Plate A. Fig. 22.)

Ceriodaphnia qtiadrangula, SARS, (fide Mcelt.eh.)

Head small, depressed, rounded at the end, not angulated; forni-
ces prominent; shell roundish, or sub-quadrangular, moderately
reticulated; antennules rather large; post-abdomnen broad, nar-
rowed from the middle to the end; the nine or ten small anal spines
nearly equal; claws large and smooth. In P. E. Mueller's time
males unknown. Length 1 mm. Specimens 0.6 mm. long from
Minnesota agree in most respects, but the reticulation is very
marked and irregular and the terminal claws are pectinate. This
form constitutes a transition to the next.

A species related to C. laticaudata, but only half the size, was
found in Clarke's lake, a small but very deep pool, containing a
fauna like that of the great lakes. The appearance is like the
small form alluded to under that species, but the claws are smooth,
the head is slender and strongly angled behind the eyes, and the
antennules are of rather large size. The foruices are not very

40 TWELFTH ANNUAL REPORT.

prominent. The shell is large-reticulate and the abdomen is large
and obliquely truncate, the anal teeth being: very large and strongly
curved. The only individuals seen were ephippial females measur-
ing .55 mm. This may be.

,Sp. lO. Ceriodaplmia coiisors, Birge.

This species differs from C. laticaudata in one or two points,
being about one-half the size and having fewer caudal teeth. Birge
says the abdomen is broad and obliquely truncate. The difference
between being obliquely truncate and narrowed at the end in some
circumstances disappears, so that really this species seems quite
close to laticaudata.

Found in Madison, Wis.

Sp, 11. Ceriotlapliiiia quadraugiila, Mueller.
(Plate A. Figs. 17-18,)

Daphnia quadranr/ida, O. F. MUKLJLEB.

Dnphnia reticulata, BAIED.

Ceriodaphnia quadrangida, P. E. MUELI.EB.

Head depressed, rounded at the end, only slightly angled; forni-
ces prominent, antenuules large; post-abdomen narrow, of equal
width for the lower half, rounded at the end, with about eight
small spines; claws smooth, length about 0.6 mm. This species
rf^sembles a smooth-clawed D. reticulata.

Sp. 12. Ceriodaphnia scitula, (Sp. n.)

(Plate B. Figs. 5-7.)

One of the most abundant species of Ceriodaphnia in Minnesota
is a large form much resembling C. quadrangula. The post-ab-
domen is exactly as in C. reticulata or C. dentata, which latter it
resembles in having a sharp angulation in front of the anteunules.
The shell is oblong and hea,vily marked with minute, regular hex-
agonal lining; the upper angle is rather sharp. The head is closely
appressed, the fornices are prominent and abruptly truncate at the
tip, the eye is small, the pigment fleck also small; antennules short.
The post-abdomen is of moderate size, narrowed toward the end
and armed with about ten powerful curved spines; the terminal
claw itself is large and curved, armed only with fine spines extend-
ing down the entire inner side. The size is 0.8 — 1,0 mm.; color
pinkish, opaque; antennae, especially, often bright pink. Male 0.6

STATE GEOLOGIST. 41

mm., flagellumof the male antennae long; sensory filaments lateral,
also one anterior, lateral flagellum.

Distinguished from C. quadrangula by the prominent fornices,
large anal ^spines, small reticulations, form of head and larger size

A small variety resembling the above very closely is the com-
monest form in our larger lakes; the reticulation is commonly
larger but less distinct, the head is depressed and narrowed, with a
sinuous upper outline. The fornices are prominent and the form
of the post-abdomen is exactly as in the last. The spines of the
post-abdomen are very long and seated on small eminences. The
length hardly exceeds .55 mm. The claw is densely ciliated, but
not spined; these smaller forms have but few eggs (two). The
young have a thorn on the angle of the fornices. Plate J. Fig. 1
I'epresents the ephippial female of this species. There seems no
reason to doubt that this is only a variety of C. scitula. The small
form of C. reticulata mentioned by Kurz might be referred here,
while the larger form with less prominent fornices is not so diflfier-
€nt from the American C. dentata.

Sp. 13. Ceriodaphnia nitida, Schcedler.

Ceriodaphnia quadrangula, LeydiG.

This species seems to be characterized by the quadrangular form
of the meshes of the shell-markings and the presence of teeth
«pon the claws,

Sp. 14. Ceriodaphnia textilis, Dana.

This species is not sufficiently fully figured to allow of a sug-
gestion as to its affinities.

Daphnia rotundata, Say, is very probably a member of this
genus, though the description is hardly intelligible. "Body
rounded behind; upper antennae three-branched, a small spine
above at the joints; lower five-branched; color white. Length 0.5."
It is probable that we should read ''upper branch of antennae with
three setse", etc., in which case we maj' identify the above with
€hydorus or the like.

III. — Genus Scapholeberis.

The genus Scapholeberis stands rather closely related to Cerio-
daphnia, from which it is at once distinguished by the angled or
spined lower posterior angle of the shell. The head is rather

42 TWELFTH ANNUAL REPORT.

clumsy, and the continuation of the fornices runs toward the apex
of the incurved beak, which commonly lies within the valves of the
shell. The lower anterior augle has a prominence and there is a
basin-shaped area inclosing the base of the antennae, part of which
lies on the shell and part on the head. This area is more strongly
lined or reticulated than the rest of the shell. The lower margin
is straight and terminates, in most forms, in a long scythe-shaped
spine which is directed backward. The shell itself is usually indis-
tinctly reticulate or unmarked, and commonly is deep colored. The
post-abdomen is very like Ceriodaphnia or more as in Simocephalus;
the anal spines are few and the older specimens have more thau the
young; the place at which additional spines are to appear is
marked by prominences. The eye is of moderate size, the pig-
ment fleck rather small and the antennules short and hidden by the
beak. The antennae are of small size and generally dark colored.
The ephippium contains but one egg; the males do not have al-
tered antennae or feet. The sexual periods fall in early summer
and in autumn, according to Weisraann; the males appear but
sparingly. The species S. mucronata is very abundant every-
where, while the others are less frequently seen.

Sp. 1. Scapholeberis inucroniata, Mueller.
(Plate J. Fig. 5.)

Daphnia mucronata, Mueller, Leivin, LilljebORG, FiSCHKR, LeYDIG, BairD,

Herrick.
Scapholeberismucronata, SchoedIjEr, P. E. Mueller, Kukz, Weismann, Bikge^

Herrick.

This well-known species with rather short spines below is found
abundantly everywhere. In this country at least it is character-
ized by a dark color. The head is large, rounded in front of the
large eye, serrate below and extending posteriorly into a roundish
beak, back of which are the short antennules. The fornices are
very short and rounded; a line connects the fornices with the beak
by a sudden deflection downward; it sets off' the area which forms
a part of the basin of the antennae. A second line springing from
just above the termination of the fornices passes over the eye by a
broad curve. The post-abdomen is truncate and bears beside the
terminal claws four or more spines which rapidly decrease in sizi'.
The claws are minutely spined; the spines on the shell are of vari-
able length, but do not exceed one-fourth the length of the re-
mainder of the lower margin. This species ranges overall Europe
and eastern United States.

Length 0.6 mm. — 0.8 mm.

STATE GEOLOGIST. 43

Sp. 2. Seaplioleberis corniita, SchceJler.
(Plate T. Fig. 6.)

Monoculus bispiiiosus, DeCtKKR.

Daphnin mucronata, var. acute rostrala. Baird.

Scapholeberis mucronata, var. f route cornula, P. E. MUELLER.

This species diflfers from the above only in having a sharp curved
horn on the head in front of the eye. The use of this appendage-
can only be coujectured; but it may be that, like the curved beak
of Ripophilus, it serves to clear away rubbish in the filth in which
these animals frequently live. This form, be it variety or species^
is not known in America.

Sp. 3. Scapholeberis ariuata, (Henick.)
(Plate B. Figs. 10-11.)

Scapholeberis mucronata. var. armata, Heeeick.

A very beautiful and unique species, which possesses the extreme
development of the peculiarities ot the genus. The head is shaped
very much as in the previous species, the fornix is squarish, th&
basin for the antennae is small. The upper lines from the fornix
meet behind the eye; the form of the shell is as in the above, but
the spines upon the lower margin are longer. The scythe-like
spine on the lower angles of the valves is extremely long, falling
little short, in extreme cases, of being as long as the entire lower
margin, in others about one-half as long. There are the usual
lines parallel to the lower edge of the shell. The specimens hav-
ing the longest spines were found in fresh water about Mobile,
Ala., but the species occurs in Minnesota and intermediate points^
though sparingly.

Sp.4: Scapholeberis nasuta, Birge.

Form much as in the last, head shorter, "prolonged into a
rather sharp beak, at whose apex the continuations of the fornices
unite. The beak does not project downward as in S. mucronata,
but backward, and in its natural position lies between the valves."
The usual reticulated and lined areas are present and the balance of
the shell is covered with ''small pointed projections." "The anten-
nules are much larger than in S. mucronata, though they do not
project beyond the rostrum." The pigment fleck is long and
large; the post-abdomen is much as in the preceding species; the
terminal claws have several fine teeth. The males have the open-

44 TWELFTH ANNUAL REPORT,

ing of the vas deferens close behind the terminal claws; macro
short and blunt, length 1 mm. This species is very near the next,
but differs in several particulars. It forms the transition to the
next, which is the extreme of the genus in a direction converse to
that pursued by the S. armata.

Sp, 5. Scapholeberis angiilata, Henick.
(Plate B. Fig. 9, Plate T. Fig. 7.)

American Naturalist, 1883.

Form as in the above, but comparatively larger; valves quadran-
gular, anterior margin strongly arched; head short, only slightly
concave below the eyes; the beak is as in S. nasuta, but seems to
be directed more nearly directly downward than in that species.
The anteunules are long and resemble those of Simocephalus. The
pigment fleck is square and rather large; the antennae are of the
usual size. The reticulated areas are as in the other species. The
post-abdomen is more as in Daphnia, not so squarely truncate and
with five to seven large teeth; the first foot has one elongated
jointed seta; the posterior angle of the shell has no spine, at most
there is a somewhat prominent acute angle, the inner shell layer
is armed at this point with some elongated teeth as in the corres-
ponding situation in Simocephalus. On the whole, there is a
similiarity to that genus in this as well as in the previous species.
S. nasuta has a short spine and elongated pigment fleck; the pres-
ent species has a squarish but rather large fleck and no spine; the
post-abdomen has a greater number of spines than any other
species. South of Tennessee river, in Alabama and Mississippi.

The species of this genus are predominatingly American, four
■out of the five being found in the United States; the fifth, more-
over, is more often regarded a variety of one of the others; in fact,
the absence of S. cornuta from America is one of the most impor-
tant supports of the specific independence of the two forms. All
the species delight in disporting themselves near the surface in
«unny weather.

lY. — Genus Simocephalus.

Although a very well circumscribed group, this genus passes
into the next rather directly by means of S. macrothroides. The
connection on the other hand seems to be by the way of Scaphole-
beris, though there is a rather broad separation between even
Scapholeberis angulata and any known Simocephalus. The en-

STATE GEOLOGIST. 45

larged spines near the angle of the shell and the form of the an-
tennules as well as some other points, show a transition through
that species toward the present genus. The general form is quad-
rate Avith the lower posterior margin sinuate; in young specimens
the shell is nearly a perfect rectangle. The upper margin is pro-
duced more or less at the point of union with the free posterior
margin and the shell is either arched or very abruptly angled
above the prominence in old females. The head is produced into
a projection at the eye while the beak propt r is between the ante-
rior margins of the valves; the pigment fleck is rather large and
variously shaped. The fornices are larg^er than in Scapholeberis-
and extend to the front of the head over the eyes; the antennules
have a lateral flagellum which is large and lance-shaped. The
post-abdomen varies very little in shape; it is truncate and exca-
vated below and very broad. The anal teeth are few, large,curved,
pectinate; the claws are straightish and pectinate or spined; the
labrum is shaped as in Daphnia; the anterior part of the stomach
has the usual ca^ca.

The members of this genus are among the most abundant and
conspicuous of the family and are more persistent during the
changing seasons than any other form. S. vetulus, the common-
est species, stands in the centre of the genus, while two extremes
are expressed by the other members of the group.

The winter or sexually produced eggs are lodged in
an ephippium or saddle- like modification of the shell, which is
finely reticulate; while the shell is usually marked by fine'anasta-
mosing lines which, in some species, show clearly their derivation
from a rather fine hexagonal marking.

The sexual periods, wheu males are produced, occur in autumrt
and spring. The males have few distinguishing characteristics^
the form being that of the young female.

The opening of the vasa differentia is back of the anus, hence
these ducts cross the course of the intestine. They have ejacula-
tory muscles about the lower part. The smaller species are fre-
quently deeply colored with pink, purple and brown fatty deposits
and the markings are more conspicuous than in the American
Eurycercus, which is itself often brightly spotted with blue or pur-
ple. The aspect in the water is between that of Eurycercus and
Daphnia.

The first mention made of any member of this genus in America is
Say's description, repeated in Dekay's Crustacea of New York, of
Daphnia angulata. This description which follows is quite sufii-

46 TWELFTH ANNUAL REPORT.

cient to identify the genus, and indeed to indicate that either S.
^mericanus or a related form is intended, but it is hardly compe-
tent to alter names the significance of which is quite clear.

"Sides striate with numerous parallel minute oblique lines; hind
■edge of the body with a prominent angle in the middle. Antennas
with four filaments on the upper and five or the lower branch,
dolor white or red. Length 0.1; stagnant water in the forests of
the Southern States."

Sp. 1. Siniocephalus vetulus, Mueller.

Daphnia vetula, Baikd, HekriCK.

Xfaphnia sima, MUELLER, LaTREILLE, BOSC, RAMDOHR, GRUITHUISEV. DeSMAREST

Lamarck, M. Edv7Ard:>, Koch, Gmelin, -Manuel, JuRixii, Lil-

L.IEBORG, LEYDIG.

■Simocephalus vehdus, SCHOEDLKn, P.. E. MUELLER.'KUFZ, Weismann, Claus, Lutz,
BIKGE.

This commonest and one of the largest species is apparently dis-
tributed over the northern hemisphere and abounds in all the
more shallow lakes. The head is rounded in front and is not an-
gled between the prominence of the eye avid the beak. The bod}'
is very large and not abruptly angled above, the spine of the shell
being inconspicuous and high, so that the free posterior
•edges of the shell lack little of equalling the greatest hight of
the shell. The shell is covered with minute dense striations which
spring from the free edges. The pigment fleck is elongated in old
specimens and the upper angle follows up beside the suture sepa-
rating the antennary basin from the rest of the shell of the head.
The antennules are ornamented with minute spines. At the lower
^ugle of the shell are three curved spines w^hich differ from the
preceding filaments. The number of eggs which are produced
at once is truly immense. Under favorable circumstances this
species reaches a large size, falling little if any short of 3 mm. S.
vetulus lives, by preference, among the leaves of aquatic vegeta-
tion. With us this species seems to live in the smaller pools as
well as in lakes of some size. I am not able to see any difference
in this respect between the various species.

Sp. 2. Simoceplialiis serrulatiis. Kcch.

Daphnia serrulata, KoCH, LlEVIN. FISCHER, LiLLJEBORG.
Siniocephalus serrulatiis, Leydig, Schoedlkr, P. E. MUELLER, KURZ.

Head narrow, extending anteriorly into a sharp spiny angle in
front of the eye. Dorsal line of the shell abruptly angled or
•curved posteriorly, projecting to form a broad obtuse spine behind;

STATE GEOLOGIST. 47

this spine is serrate with sharp teeth and lies somewhat above the
middle of the hight of the animal, so that the free posterior mar-
gins of the shell fall much short of reaching the greatest hight
of the shell. Post-abdomen of the usual form, with the claws
armed with two series of spines or bristles, the outer being much
the larger; anal teeth curved or angled, dentate; pigment fleck tri-
angular or rhomboidal. Length 2.0 mm., 2.5 mm.

I am not sure that the three following species are more than
varieties; the first in particular is very close to the European type.

Sp. 3.— Simocephalus congener, Birge.

My own observations of this form made throughout the Missis-
sippi valley are not in complete accord with the description of
Birge, but it seems improbable that there is any mistake in the
identification. The very generally distributed form on which this
species rests is subject to marked variations within certain limits.
This species differs from S. serrulatus in the following points.
The head, although prominent and spiny near the eye, is not an-
gled between this prominence and the beak; in fact, it is either
straight or simply curved. The pigment fleck is usually rhom-
boidal and only occasionally oval, triangular or irregular. In
other respects the agreement is rather close; the terminal claws
hare two series of spines, one of which is larger (not, as said by
Birge, equal); the outer series is not so much larger as in S. rostra-
ius, but not nearly as inconspicuous as in S. vetulus. The termi-
nal claws are rather evenly curved. This species is frequently col-
ored with pink or brown markings. In old females the back is
squarely angled above, forming a pocket for the eggs. The size
falls short of that of the last species. I have found this species from
the gulf of Mexico to Minnesota.

Sp. 4. — Simocephalus rostratus. (Sp. n.)

This form is of the size and color of S. americanus, and approaches
nearest to Schodler's S. expinosus in general characters. The back
is arched above but not abruptly angled; the spine is as in S. amer-
icanus but not so low. The free posterior shell margins are some-
what shorter than the greatest hight of the shell. The head is
produced below the eyes in an angle like a right angle, which is
not spiny. The lower margin of the head is excavated to form a
right angle, and in front of the smooth antennules forms a very
prominent beak, beyond which the antennules reach but a short

48 TWELFTH ANNUAL REPORT.

distance. The terminal claws of the post-abdomen are straightish
and are more heavily spined than in the preceding; the anal spines
are doubly curved or geniculate. The pigment fleck is rhomboid
or pentagonal; the antennules are smooth. The abdominal pro-
cesses differ somewhat from the previous species, in which the second
one is rounded above, for in this it is squarely truncate. This
species was found only in shallow pools at Ocean Springs, Missis-
sippi, and was very carefully compared with S. americanus which
is also found there.

Sp. 5. Simocephalus exspiiiosus, Koch.

Head extending into an obtuse angle at the eye, pigment fleck
rhomboidal. Shell without a spine; maximum hight of the shell
greater than that of the free posterior margm. Caudal claws with
an unequal series of spines; anal spines evenly curved. There is
little to distinguish the above from this species save the geniculate
anal spines and the presence of a blunt spine on the shell.

Var. congener, Schoedler,
has the lower outline of the head sinuate instead of angled.

'&'

Sp. 6. Simoceplialus daphnoides, Hernck.

American Naturalist, 1883.

A curious transition form, found only south of the Tennessee
river, was described in the American Naturalist in May, 1883, under
this name. By an oversight a comparison made with S. americanus
appeared as though made with S. vetulus. The general shape is
oval; the greatest hight of the valves lies near the middle and not
posterior to it as in all the other species. The head is short, de-
pressed, rounded in front; the beak is wanting; the lower margin
of the head is straight. The pigment fleck is small, oval or irreg-
ular; the fornices are small and short. The antennules are smooth.
The post-abdomen is narrow, shaped more as in Daphnia; the
terminal claws are straightish and fringed part way with spines;
the anal spines are slightly curved. The processes of the abdomen
are long, as in Daphnia. The shell is covered by the characteristic
striations and extends into a blunt spine. In every detail, almost,
there is an approach toward the genius Daphnia, while the general
result is sufiiciently like Simocephalus. The lower angle of the
shell is not armed with the peculiar curved spines as in all the other

STATE GEOLOGIST. 49

species. This species becomes over 1-10 inch long. In such old
individuals the spine is nearly midway of the hight.

One could wish a trifle closer link to Scapholeberis than that furn-
ished by S. angulata; but, on the whole, the'position of this genus
can not well be called in question. America has four species out
of the six known and but one of these certainly identical with the
European, though others are probably too closely related.
Note.— On p. 47 read S. Americanus, Birge, not S. Congener.

V. Genus Daphnia.

Long considered the type of the family, this genus is most fre-
quently seen, or, at least, is more conspicuous than any other
group. It has already been pointed out that the forms here
united are the extreme development of a diverging line. Simoceph-
alus is the link connecting it with the typical forms of the fam-
ily. As might be expected, this genus presents more puzzling
problems than any of the others. It contains more peculiarities
of structure and diversities of habit and development than any
other of the genera. Here the sexual differences are most inter-
esting. The young are hatched with a pendant appendage at-
tached to the upper posterior angle of the shell, which soon be-
comes the rigid spine characteristic of the younger stages and
males of the genus. The females almost immediately after birth
commence the production of eggs by an asexual process. Groups of
epithelial cells containing four each are formed and one of the
cells of each group develops at the expense of the others, forming
the egg. Many such eggs are laid simultaneously and deposited in
the cavity between the shell and the dorsal part of the animal.
The eggs are prevented from escaping by means of three long pro-
cesses, of which the first is much the larger and curves forward.
At stated periods in spring and autumn the males appear; the fe-
males of the generation in which occur the males have a tendency
to produce eggs of a different sort charged with a different mis-
sion. At the same time the upper portion of the shell (that sur-
rounding the brood cavity) becomes finely reticulated and pigment
is deposited between its layers. This ephippium, as it is called, in
allusion to its saddle-like form, is the case in which the winter egg
is to pass the period of cold or drought which is to follow. The
method of the formation of the ephippium is obscure and, in
spite of the investigations of Lubbock and Smitt, considerable re-
mains to be learned with reference to this interesting modification
of the shell. Some rather careful study has been devoted to this
4

;^c'^Q

50 TWELFTH ANNUAL REPORT.

subject by the writer, but it was unfortunately interrupted before
completion. The most promising method of persuing the investi-
gation is that of sectioning ephippial females in various stages
with the microtome. A preparation of soap was employed with
partial success as a medium for embedding, and figures of some of
the many sections made are drawn on plate P. Figure 10 is a ver-
tical section through the middle of an ephippium which has been
cast off. The outer and inner shell layers are distinct and one of
the eggs is divided in the middle. No pigment or protecting ma-
terial was deposited in this case, which is the simplest possible.
Fig. 9 represents a section just back of the head; it passes diagon-
ally, severing the heart longitudinally (h). The intestine (a), the
ovaries (g), the mandible (m), the labrum (1), and certain suspen-
sorial muscles (?) are seen in situ. Only a portion of the ephip-
pium is cut and the double layers enclose a large mass of protec-
tive matter. Fig. 8 is a vertical section through the middle of the
animal, and the usual form of the ephippium is seen with its large
amount of protective matter obscuring all else. Fig. 7 is a longi-
tudinal section of an ephippium similar to that seen in Fig. 10. It
is hoped to present at some more appropriate time a fuller account
of the formation and process of moulting this saddle.

Development of Daphnia.

Although the careful researches of Clans and Grobben have ad-
ded much to our otherwise rather meager knowledge of the develop-
ment of the cladocera, there still remain many interesting points,
particularly with reference to the individual species, which merit
careful study.

The following observations relate to the single species (D.
schffifferi) which was available during a short stay in Leipzig:

The winter eggs of D. schasflferi are t\\o in number and are
lodged in the well known manner in an ephippium.

The shape of these eggs is sharply ovoid, there being no distin-
guishable difference between the two ends. The position in the
ephippium is not, as might be expected, with the longer diameter
paralled to the axis of the body, but the posterior end is slightly
elevated. This is undoubtedly due to frequent elevation of the
abdomen between the valves during the extrusion of the eggs.

The color is dark green and the only protection as the egg leaves
the ovary is a thick, tough shell which is at firEt so soft as to be
susceptible to pressure. It is thus reticulated, apparently through
the simple pressure of the walls of the ephippium.

STATE GEOLOGIST. 51

The length is 0.43 mm.; width .33 mm. in the average, though
eggs were occasionally found of an elongated form, measuring .48,
,31 mm. The contents of the egg consist of spheres of greenish
plasma of various sizes and fat or oil drops. These oil globules are
not very numerous as compared with those of the summer eggs,
and likewise never attain the dominant size seen in the latter.
The various forms assumed by the plasma balls are perplexing but
frequently result from the action of external agents. The cleavage
stage was not seen, and if actual segmentation takes place, it
must be inconspicuous as would be expected from the large quan-
tity of yolk present. The differentiation of the blastoderm occurs
very early, perhaps in the ovary itself, and the result is a tolerably
uniform layer of prismatic cells. The egg now comes to a period
of repose after the blastoderm has produced a second external
envelope apparently by simple secretion.

This envelope consists of a fine structureless membrane. The
€gg, under ordinary circumstances, remains dormant during the
winter in this most favorable stage. The reason for which is evi-
dently the fact that the differentiation has proceeded to the extent
of producing the greatest number of protective layers without
materially increasing the complexity, and thus the sensitiveness, of
the organism. Under favorable circumstances the development
proceeds farther and near one pole appears a slight indenture of
the surface which grows deeper and seems to form a true invagina-
tion. This blastopore, if such it really be, remains for some time,
generally till the two " scheitel " plates appear. These "scheitel-
platte " are formed by a simultaneous thickening and lengthening
of the cells of limited areas on opposite sides of the egg, near the
opposite pole from that occupied by the blastopore. The "scheitel-
platte" are situated at right angles to a plane perpendicular to the
blastopore. The nuclei of the cells of the "scheitelplatte" are
nearly .0208 mm. in diameter, while those of the other blastoderm
cells are about half that size.

The egg remains a long time in this stage, while the following
stages are passed through quite rapidly till the embryo assumes its
nauplius form. The remainder of the development agrees, so far
as seen, quite fully with that of the summer eggs, to which we will
now return.

The summer eggs vary greatly in size and number, but are
nearly as large as the winter eggs. The number is sometimes re-
duced to two or three or rises to as many as fifteen or even more.
In color the eggs also vary from green to brown. The fresh egg

52 TWELFTH ANNUAL KEPORT.

consists, as the winter egg, of two sorts of yolk spheres. The
plasma or formative yolk contains colored globules of rather small
size, distributed throughout the whole of the mass quite uniformly.
The food yolk or oil globules assort themselves in two sizes; first,
a few (generally three) very large oil drops, which persist through-
out the ealier stages of the embryo; second, smaller globules of ap-
parently the same character, which are quite numerous and form a
very considerable part of the contents of the egg, In an egg of
about .35 mm. in diameter, the largest of the smaller size of oil
drops measured .029 mm. while the larger three exceeded .060 mm.
The oil drops are distinguishable by their light refractive
power, pellucidity and the intense dark brown or black color assum-
ed when treated with osmic acid. The latter reagent affects the
formative yolk but slightly. It will be seen that though the sum-
mer egg is nearly as large as the '' dauerei " in some cases,
yet the relative amount of formative yolk is more diverse than at
first appears.

The great similarity between the two sorts of eggs in Daphnia
schaefferi is throughout striking as compared with Moina, the only
one of the Daphnidae the development of which is fully studied.
In the summer eggs I have not been able to see the complete seg-
mentation described for Moina. The following stages are much
as described by Grobben. An invagination occurs and a median
swelling appears on the ventral aspect of the egg.

Labrura and second antennae bud out and are soon followed by
the antennae, mandibles and two pairs of maxilla3, after which the
five pairs of feet soon appear. In an early stage there is present a
basal palpus to the second antennae, a fact not before observed, and
this persists as the small two-bristled wart found on the basal joint
of the antenna. It is a conspicuous object in the embryo and is
thus a true embryonic organ.

The eyes of the embryo appear as two separate pigmented flecks
which approximate and are covered with an oval refractive body,
which later is penetrated by the pigment and divides to form the
small lenses. Soon after this the shell grows over the eye as de-
scribed for Moina.

The first indication of the shell appears as two folds of the max-
illary region of the back, being thickest laterally. These grow
forward and backward to form the cephalic and body shield. At
a little later stage there appears a very interesting modification of
the shell which stands in close relation to the growth of the brood
sac. A slight protuberance appears on the margin of the shell in

STATE GEOLOGIST. 5B

the median dorsal line and extends toward the abdomen. It
grows much more rapidly than the other parts of the shell and, in
a later stage, forms a comparatively enormous tail, which curves
under the animal between the shell valves which now extend be-
yond the body. This "tail" extends well along the ventral mar-
gin of the shell and reminds, by its position, of the tail of a fright-
ened dog. The true tail, or post-abdomen, is, in the meanwhile,
well developed and is constantly kicking the useless protuberence
of the shell upwards. As the animal leaves the egg this projec-
tion becomes straightened as in the young D. pulex, finally be-
coming the still considerable spine, though it is proportionately
much shorter than in the embryo. The spine becomes shorter
with successive moults and the mature form has only a slight
rounded knob in place of a spine more than half the length of
the body.

The use of the long spine in the young Daphnia is a matter of
interest. Its length agrees pretty well with that of the brood
<3avity and it seems possible that it serves to prevent the shell
from bending abruptly down when it is only partially removed
during the moult and thus breaking off and so leaving a portion
of the clothing of the brood-cavity therein to become a source of
irritation. This is more necessary for the young since the brood
■cavity is narrow and the shell weak, so that while the outer shell
is removed like a glove from the finger, it can not be pulled up-
ward Of downward, but directly backwards. It is well known that
male Daphnige often have the spine, while the females may have
none, and here again it is possible that the narrower cavity over
the abdomen requires this assistance, while this is not the case
with the females.

The shell gland is early formed and the branchial lamellae of the
feet appear almost simultaneously with the feet themselves as
distinct lobes. The branchial chamber is not a simple chamber, but
is essentially a curved tube as can be very well seen in the last foot
of the adult. This tube doubles upon itself and crosses in the
manner of a loop and a constant stream flows rapidly through it.

The nervous system is, at first, paired from beginning to end
and first unites anteriorly, the ocular ganglia fuse after the union
of the two pigment flecks in the compound eye, then the cephalic
ganglion is formed by the union of the two preoe3ophagal ganglia,
the commissures passing about the oesophagus. I have not been
able to determine if the suboesophagal ganglia become fused.
From the anterior ganglia spring the nerves to the autennae and

54 TWELFTH ANNUAL REPORT.

jaws, which latter are the larger in the embryo, being exceedingly
large nerves.

This key contains the majority of the genus, but falls short of
completeness. The following species are uncertain. W. Schman-
kewitsch described as new D. degenerata and D. rudis, from salt
or brackish waters. These he regards as degenerate forms produced
by the inferior aeration of dense waters. The author does not
appear to recognize the modern distinctions of genera so that, not
having seen the work, even the generic position can not be defi-
nitely stated. His investigations seem to show that the proximity
of salt waters influence the form of the body, or, perhaps, that
there is a constant interchange between the sub-marine and fresh-
water species. Daphnia hrevicauda^ Chambers, is an incorrectly-
figured and described Simocephalus.

Key to the Genus Daphnia.
Section i. Pigment fleck present.

A. Head short, equally rounded.

1. Z). psiWacea, Baird.

B. Head not regularly rounded, more or less beaked.

(a) Claws spiny.

I. Abdomen broad, series of anal spines nearly equal, neither head uor back
keeled.

t A marked sinuosity in the posterior outline of post-abdomen.

2. D. schiefferi, Baird.
D. ovata, Sars.

D. pennata, Mueller.
++ No well marked depression.

3. D. pulex, Mueller.

4. D. sehcedleri, Sars.
D. hastata, Sars.

X>. obtusa, Kurz.

II. Abdomen narrow, shell keeled somewhat dorsally.

5. D. minnehaha, sp. n.

6. D. carinata, Sars.

(b) Claws nearly or quite smooth.
I. Head not crested.

7. D. longispina, Leydig.

8. D. rosea, Sars-

9. D. similis,ClSiMS '
D. lacustris, Sars.

D. cavitrons, Sars.

10. D. hyalina. Leydig.

11. D. dubia, Herrick.

STATE GEOLOGIST. 55

D. pellucida, P. E. Mueller.
D. galeata, Sars.
12. ( ?) D. Isevis, Birge.

Section ii. Pigment fleck absent.

A. Head but slightly crested.
1. -D. longiremis, Sars.

B. Head Strongly crested.
■>. D. cristala, Sars.

3. D. cucuUata, Sars.
D. apicata, Kurz.

4. D. knlbergemis, Schoedler.
D. cederstrorali, Schoedler.
D. retrocurva, Forbes,

D. vitrea, Kurz.

5. D. magiiiceps,sp. n.

Section I.

A. Head shorty evenly curved.

Sp. 1. Dapliiiia psittacea, Baird.

Mentioned by Schoedler, Fkic and Kvrz.

This species is at once recognized by the head, which is very
short and evenly curved, or nearly so, from the heart to the beak.
The shell is high, oval, with a rather short spine. The fornices
are wide and angled behind; the antennules are longer than in
most species; the post-abdomen is very large, but narrows toward
the end and has comparatively few anal teeth, which are of une-
qual bize. This is one of the largest of the genus. Not yet
found in America.

B. Head more or less concave below, at least not evenly arched.

Sp. 2. Dapliiiia schseflPeri, Baird.
(Plate M. Figs. 1—4.)

Daphnia pennata, MUELLEB.

Daphnia pulex, STRAUS, KOCH, (flde P. E. MUBfKLER.)
Vaphnia magna, LILL.JEBORG, Leydig, etc.
Daphnia schiefferi, SCHOEDLER, KuEZ.

The largest species of the genus, is of an elongated oval and
veutricose form. The spine is entirely absent in old females and of
only moderate length in the young. The antennules of the male
are long and have a very long flagellum. The post- abdomen is
narrowed suddenly below the anus so that the spines consist of
two sets; the terminal claws are spiny at the base. Although

56 TWELFTH ANNUAL REPOKT.

very similar to D. pulex, it may be recognized at once by the con-
cavity of the dorsal margin of the post-abdomen. The plate will
make any detailed description superfluous. A common species in
Europe, but not yet found in America.

Daphnia ovata, Sars, seems probably this species, but Sars was
troubled by Straus' mistaken reference.

Dcqjhnia 2)ennata of Sars may al^o be this species or, more prob-
ably, D. pulex. The Latin discription given by Sars is appended
for convenience of reference.

Daphnia pennata, Sars.

"Antecedenti (D. pulex) similllma, caput autem a latere visum latius, rostro breviore,
supra visum testa cetera pirum angustius fere cordiforme, antice acuminatum. Pro-
cessus anteriores duo disjuncti. Margo posterior postabdominis in medio sinulo parvo
et infra hunc utrinque aculeis 16-18 armatus. Color ut in antecedente. Longit.2%mm.''

Daphnia ovata, Sars.

"Caput a latere visum ante oculum fere angulatum.margiue inferioreleviter concavo
In rostrum longum apicem versus attenuatum, extremitate tenuissima exeunte, spura
visum ut in D. pennata cordiforme. Testa cetera a latere visa ovata, margine superi-
ore et Inferiore in femina adulta fere ajqures arcuatis, postice in medio spinam formans
brevissimam vel oninino obsoletam. Processus anteriores duo abdominis disjuncti-
Margo posterior postabdominis in medio sinuatus, utrinque aculeis 20-22 armatus. Color
albido— flavescens vel-virescens. Longit. circit 3 mm."

Sp. 3. Daphnia pulex, Mueller

This commonest of our Daphnids is apparently circumpolar in
distribution. I have found it in Alabama near the Gulf and it also
occurs near lake Superior.

Oval, either elongate or short, spine springing from the upper
angle of shell or in some cases near the middle. The spine is rather
long in young individuals but becomes very narrow in older ones
or entirely disappears. The abdominal processes are long, not
coalescent, or slightly united at the base. The head is concave be-
low and extends into a prominent beak. This species is either very
variable or several species are frequently united under the
term. Two types have been recognized in America. One, abun-
dant in spring in smaller ponds in Minnesota, is rather short,
arched above, and in old females with the spine situated near the
middle of the posterior margin. This form is quite typical for the
species and occurs from April to mid-summer. Another variety was
found in Alabama in late autumn, and similar animals in mid-winter
in lake Calhoun, Minnesota. This type has a much more elongate
body, the very slender but rather short spine springs from the upper

STATE GEOLOGIST. 57

margin of the shell or is quite wanting. This longer form has the beak
slightly arched so as to resemble a "Roman nose." The anal spines
are less numerous (10-14 while typical D. pulex has nearly 20).
The young of this form, which may be called

Daphnia pulex, var. nasiitus, (Var. n.)

(Plate N. Figs. 1-4.)

vary much among themselves but, in general, resemble the young
of the European form.

Daphnia pulex has been mentioned by a number of authors in
America, Smith, Birge, Chambers and Herrick having noted its
occurrence in various parts ol the United States. D. ohtusa, Kurz,
is apparently only the spineless condition of the above or a related
species. No Daphnia is without the spine through life; such a
form would constitute a new genus at once.

Sp. 4. D. sclioedleri, Sais.

Seems to resemble D. pulex very closely but diifers in having
the lower margin of the head nearly straight, terminating in a short
straight beak. The spine springs from the middle of the posterior
margin. The anal spines are 14-16 in number. Length 2.33 mm.

This name is applied by Sars to Schoedler's D. longispina which
is not D. longispina of Leydig.

Sars' D. hastata is so insufficiently defined that it will probably
be necessary to drop it from the list.

Sp. 5. Daphnia niiiinehaha, (Sp, n )

(Plate K, Figs. 1, 2; Plate L, Figs. 1, 2.)

This species, which occurs in small pools in autumn (afiluents of
Minnehaha creek, etc.,) closely corresponds apparently to Sars'
Daphnia carinata but differs in numerous points. It, in fact, is more
nearly related to D. pulex than the group under which that species
is placed.

The form is oval, arched above, narrowed posteriosly, terminat-
ing in a rather short spine which curves lightly upwards. In males
and young females the spine springs from the upper angle, but in old
females having many summer eggs the spine is nearly median-
The head is depressed, strongly arched and keeled slightly above
the eye, which occupies the extreme end of the forehead. The keel
of the head extends into a slight angle over the heart and continues

58 TWELFTH ANNUAL EEPOET.

down the back. In young females and in males the slight angle
is replaced by a strong knife-like projection which extends into
from 1 to 4 sharp teeth, the anterior tooth being directed forward.
The males, in particular, have this feature emphasized. D. long-
ispina has a somewhat similar projection but the more nearly re-
lated forms seem not to show this peculiarity. The beak is slightly
curved and the lower margin of the head is slightly sinuate. The
shell has the usual square reticulations and is usually very trans-
parent but in peaty waters becomes brownish. The size is smalt
but variable; 1.8 mm. is a common measurement. The post-abdo-
men is narrow, the claws are armed with four or more teeth and a
series of lateral bristles. The anal spines are eleven or more in
full grown females and decrease only moderately upward. The
processes of the abdomen are distinct. The males are smaller and
strongly carinated above and of the same form as young females
The antennules are rather long, with a short lateral and a long
terminal flagellura, which latter is more than twice the length of
sensory setas which are partially lateral. The first foot has a strong
claw and a longflagellum, while the second feet have a small spiny
hook. There is a single abdominal process which is not hairy as.
in D. pulex.

Sp. 6. Daplinia carinata, Sars.

Very similar to the last but, according to Sars, the claw has no
well marked teeth, a short flagellum on the male antenna, aud the
abdominal processes are united at the base (which may indeed be
sometimes the case in the above.)

D. cavifrons, Sars, has a prominence on the forehead and the lower
margin of the head is strongly concave, otherwise hardly destin-
guishable save by the absence of the keel above.

Sp. 7. Daphnia longispina, Mueller.
D. longispina, O. ¥. Mueller. Baird, Letdig, Sars, P. E. Mueller, Kurz. VVeis-

MANN, etc,

Oval, elongate; head large, rounded in front, lower margin some-
what concave; rostrum long. Spine very long, springing from the
middle of the posterior margin. Post-abdomen attenuated toward
the end. Terminal claws smooth or simply cilate, spines few.
The abdominal processes are united at the base a very little, Flag-
ellum of the male antennule hardly longer than the sensory sette.
The young have three teeth above as in D. minnehaha. There is

STATE GEOLOGIST. 59

a great deal of diversity of opinion as to the value of this name.
Not that there is any doubt of the existence of a widely distributed
form which in general is that intended by Leydig and others, but
the variation is so great that the possibility remains that more
than one species is included under the one title.

P. E. Mueller recognizes two varieties depending chiefly upon
the length of the spine.

Z). laciistris, Sars, is nearly related, if not a variety of the above.

Sp. 8. Daphnia rosea, Sars.

(Plate K. Figs, 10-12.)

Tn form very like D. longispina, this species, which is the only
representative of this smooth-clawed, unkeeled group yet found in
America,might perhaps be appi'opriately re-united with that species,
but, as there seems little doubt of the identification with Sars' va-
riety, as above, I prefer to use his name.

Body oval, moderately ventricose; head of moderate size, lower
margin nearly straight; eye situated in the anterior prominence.
The beak is not very prominent. The upper outline of the head
is slightly concave above the eye or rather less convex. The head
is separated from the body by a marked depression. The spine of
the shell springs from the upper angle or is quite wanting. The
post-abdomen is of moderate size, somewhat narrowed toward the
end. The claws are smooth, the anal spines nearly equal, straight,
about 14 in number. The abdominal processes are not coalesced
or but slightly so. Length 1.50 mm. to 2.0 mm. The species was
collected sparingly in a large gathering of D. pulex from a small
lake in early spring.

The size and conformation of the abdominal processes is very
variable and the long and very slender spine is frequently absent.

Sp. 9. Daphnia siniilis. Clans.

The description of this species, which was bred in confinement
from eggs brought in mud from Jerusalem, I am, unfortunately,
unable to quote. Judging however, from the figures which alone I
now have access to, it belongs in the group of D. longif^pina^ though
in many particulars it resembles D. schaefferi. The form is elon-
gate, the spine short and springing from the upper margin. The
antennule of the female is very large and flagellate, while that of the
male is like that of D. schaefieri. The flagellum and hook of the
first foot of male are rather small.

60 TWELFTH ANNUAL REPOET.

We now come to a group of related species which are most dif-
ficult to circumscribe on account of their extreme variability. Ac-
cording to the view of Lutz they would all fall into the old D.
hyalina of Leydig. More probably, however, some of these forms
are of nearly or quite specific value.

Sp. 10. Daplinia liyaliua, Leydig?

(Plate L, Figs. 3, 5.)
Daphnia longispina, Herrick.

I have elsewhere given a brief account of the post-embryonic de-
velopment of a species which agrees best with Leydig's figures of
D. hyalina.

The lower outline of the head is nearly straight, the eye being
always approximated toward it. In young specimens the head is
sharp in front and crested. The lower margin of the head appears
very long and the beak turns backward. The spine is very long in
young forms but is short in old females. The male resembles very
much the young female. The post-abdomen is narrowed toward
the end, the terminal claws are smooth, the anal teeth few and the
abdominal processes united. Our specimens are from Paducah, Ky.,
south of the Ohio river.

I do not know how to distinguish D. Icevis, Birge, from D. hyalina,
save that the abdominal processes are said to be distinct. Both
forms were observed in the above mentioned gathering. If, how-
ever, Birge's figures are characteristic, he had a difierent variety
before him from ours; it seems somewhat like D. galeata.

D. pellucida, P. E. Mueller, diff'ers from D. hyalina in the pre-
sence of a series of small teeth on the caudal claws, and a more
strongly curved beak.

It is just now brought to my attention that P. E. Mueller, in a
late work, identifies D. pellucida with D. hyalina, though he still
holds D. galeata distinct.

Daphuia galeata, Sars.

( Plate T. Figs. 7, 8.)

According to P. E. Mueller, this species differs from D. pellucida
in the absence of teeth on the caudal claw, and, in one variety, by
the acuminate head, which seems the only form for which the name
is distinctive. Kurz found only the var. frons rotundata. Accord-
ing to Forbes, both varieties, the first of which he identifies with
D. pellucida, occur in lake Michigan.

STATE GEOLOGIST. 61

S. I. Smith finds both in lake Superior, and seems to have no
doubt of their distinctness. One of the forms which 1 have seen
differs a little from either of the above, and had a different habitat.
Kurz has described the male, which has a very short flagellum upon
the antennule. A single source for D. galeata was found in a small
pool known as Clarke's lake. This is the more remarkable, as this
species, which is almost confined to larger bodies of water, is found
nowhere else in the vicinage of Minneapolis, while this minute
lake, though as deep, perhaps, as any of the largest in the county
(say 40 feet), contains a number of forms known otherwise only in
the Great Lakes, Kurz's remarks on the specimens collected by
him apply equally to these. Were the claws dentate, the animal
would pass as D. pellucida. The young have no horn on the head.
The spine of the shell is nearly as long as the whole animal in the
young. The male of our form is 1.2 mm, long, excluding the
spine which measures 47 mm. The flagellum is a very little
longer than the sensory setee, and there is a very minute lateral
flagellum. A peculiarity of this species is the scattered thorny
armature of the spine of the shell. There is but little change in
the form of head with age. The form of the last feet is peculiar.
The ephippium occupies comparatively a small part of the valves
and the spine becomes very short and quite smooth. The sexual
period occurs in September and October.

The above statements regarding D. galeata require a modifica-
tion, for in another deep lake the writer has since secured the
typical crested D, galeata with even a higher crest than that figured
by P. E. Mueller. The head ends in a sharp angle. The single
female seen was in company with the rounded variety and numbers
of D. kalbergensis, which it resembles in many respects. Oar
fauna therefore is quite complete in these remarkable forms.

( See Plate U. Fig. 6.)
Sp. 11. Daphiiia dubia, Henick.
( Plate L. Figs. V, 8.)

American Naturalist, 1883.

The life history of this form is insufficiently known, but there
seems no reason for doubting that it constitutes a new and easily
recognizable species. It is nearly related to D. hyalina, but the
head is strongly crested all round and the eye is withdrawn, in
young as well as old specimens, toward the middle of the head.
This peculiarity is shared in this degree by no other Daphnia

62 TWELFTH ANNUAL REPORT.

The form is as in D. pellucida, but the spine is more slender and
directed upward. The head is shaped much as in D. vitrea in
the young, but is much less prominent. The older form has a
shorter and more slender spine (none were seen in the ultimate or
spineless stage). The head is more evenly rounded, but still well
crested. The abdomen is very slender and the anal teeth diminish
rapidly in size from below upward. The claws are very short and
armed down the whole length with fine bristles. The abdominal
processes are well united at the base in old specimens, so that the
second seems a small process of the first. The shell is very trans-
parent and the spine" is longer than in any other Daphnid.
In a young specimen the spine was 1. mm., the body 0.7 mm., and
the head 0.4 mm. In this specimen the spine was slightly curved,
the head elongate with a slight ridge in front. Another individual
had the spine 1.1 mm. long, Avhile the remainder of the animal was
1.3" mm. This specimen also had a knife-like hyaline ridge on the
crest, which was obliquely truncate in front; it also had numerous
summer embryos in the brood sac. The spine was perfectly straight
and but slightly inclined upward. Older individuals have a rounded
crest as figured and no ridge. The spine is relatively somewhat
shorter but much more slender. The characters which most clearly
distinguish this species are the well crested head, which in young
as well as sometimes older specimens has a median hyaline ridge,
the withdrawal of the eye from the margin and the very long spine.
It resembles D. galeata in earlier stages. It is very much like D.
Iffivis or, in other words, is in the group of D. hyalina; but the study
of a considerable number of specimens from difierent localities con-
vinces me that it can not be united with that species in any of its
varieties. This species has only been found in autumn, Sept. —
Nov., lake St. Croix and Richfield in Hennepin county.

Section II.

Pigment fleck wanting. Head crested. The small, hyaline spe-
cies constituting this section, elevated by Schoeiler to the rank of
a genus ( Hyalodaphnia) and by Sars to that of a subgenus (Cepha-
loxus), are chiefly residents of the deeper parts of our larger lakes.
These forms, from their rarity, have been little studied and it is
uncertain how far the assumed specific distinctions are valid.

Two species are known in America and they are not confined to
large lakes.

STATE GEOLOGIST. 63

Sp. 1. Daphnia longiremis, Sars.

•

Hyaline, compressed, seen from the side, rounded, lower margin
strongly arched; spine long, straight, oblique. Head rounded,
lower margin nearly straight, ending in a beak directed downward,
acute anteriorly. Eye small. Antennae very long. Length 1 mm.

The abdomen is said to be similar to that of D. longispina. From
the brief description given by Sars it would appear that this spe-
cies is characterized by a rounded and uncrested or slightly crested
head. Though imperfectly described, it is here mentioned to direct
attention toward any such species as may be found in America.

Sp. 2, Daphnia cristata, Sars.

Compressed, long. Head acute in front, strongly crested, lower
margin nearly straight. Dorsal line of body little curved, spine
long in the young, strongly curved. Head of male smaller, flagel-
lum of autennule twice as long as the sette; first foot well clawed.
Length of female 1.33 mm.

Sp. 3. Daphuia cucullata, Sars.

D. be.rolmensis, Schoedler.

Very like the above, but the margin of head is not straight be-
low, is, however, extremely variable and ends in a sharp angle. The
eye lies nearly midway between the heart and the end of the head
and near the lower margin. The two anterior processes of the
abdomen are united for most of their length. The flagellum of the
male antenna is about as long as the terminal setae.

D. apicata, Kurz, seems to be a large variety lacking the sharp
spine of the head. In the main it agrees quite well. Although the
post-abdomen is broader than figured bj"- Mueller, the number of
teeth corresponds with Sars' description,

Sp. 4. Daphnia kalbergfensis, Schoedler.

(Plate U. Figs. 1—3).

Form oval, spine long. Head high, compressed, enormously
elongated, beak obtuse. Eye small. Abdominal processes not
united. Caudal claws ornamented with small setae. Antenna? of
male with a short flagellum. Length of head nearly equal to that of
body exclusive of spine.

-D. vitrea of Kurz seems not improbably a varietal form of the
above though the crest is lower, the size is less and the post-abdo-

64 TWELFTH ANNUAL REPORT.

men is more slender and has fewer teeth ; the differences are, how-
ever, hardly specific.

I am not convinced that either D. cederstromii, Schoedler, or D.
retrocurva, Forbes, are really distinct species, although the latter,
with its more strongly crested head, is said also to have a series of
teeth on the terminal claw. Perhaps it forms with D. cederstro-
mii the fifth and extreme phase of this group.

Since writing the above account of Daphnia kalbergensis this
truly monstrous species has come to light in the vicinity of Min-
neapolis. The opportunity is thus afforded to verify the suspicion
expressed above that a number of species must be united under this
name. P. E. Mueller gives the following measurements for U. kal-
bergensis: head 0.9 — 1.0mm., body 1.0 — 1.1mm., spineO.7 — 0.75mm.
Kurz for his D. vitrea gives a length of 0.85 mm. plus 0.25 mm., the
length of the spine. Judging from his figure, the head would not
measure over 0.35 mm.

Forbes says of his D. retrocurva that the head is two thirds as
long as the body.

Our specimens measured as follows:

No. 1. 1.6 mm, head somewhat more than half the body and al-
most exactly like D. vitrea in form.

No. 2. Head 0.6 mm., body 0.9 mm., spine 0.5 mm.; about 9 anal
spines. Head in this case moderately curved upward.

No. 3. Head 0.95 mm., body 0.95 or less, spine 0.5 mm.; or the
head as long as or, indeed, considerably longer than the body and
directed upward.

The males have the crest much lower, the spine longer, and the
form of antennules figured by P. E. Mueller. In the older females
the beak is elevated above the antennules, as remarked by Forbes,
but in smaller individuals there is very little difference between
our specimens and Mueller's figures.

The claws of the post-abdomen have, besides the row of fine teeth
mentioned by Mueller, a cluster of sharp teeth just at the basa.

Found, together with typical D. galeata and the rounded form, in
a small deep lake or expansion of a creek not far from Medicine
lake, Hennepin county, Minn.

Sp. 5. Daphnia magniceps, (Sp. n)

(Plate U. Fig. 15).
The peculiar form figured in the Tenth annual of this survey
seems indubitably new and is distinguished by the peculiar shovel-
shaped head, which is scarcely crested but is broadest beyond the

STATE GEOLOGIST.

65

middle. The spine is long, the claws smooth, the abdominal pro-
cesses united and the shell transparent. The eye is near the end
of the rounded head and is large; the pigment fleck was apparently-
absent. Found with Daphnia miunehaha in a shallow swampy
pool in autumn.

Family Bosminid.e.

The sole genus of the family, Bosniina, contains over a dozen
nominal species which are among the most difihcult to define of
any cladocerans. The number is here reduced to nine and the
probable position of the rejected species is indicated. This is not
done because the author presumes upon the slender material at
hand to revise the genus; but simply from the fact that the descrip-
tions of t\fb earlier writers do not permit a proper discrimination;
so that this necessity is entailed upon any one who would give a
birds-eye view of the members of the genus. The B. diaphana is
founded upon a different twist in the antennules and no hesitancy
is felt in uniting it with Sars' B. lilljeborgii. The other species,
B. brevirostris and B. nitida, are omitted simply because there
seems to be no way of separating them satisfactorily from B. mari-
tima and B. obtusirostris respectively. Three species have been
found in Minnesota, but practically no attention has been given to
the genus here.

Bosniina macrorhyncha found in Egypt is not here included, its
description being inaccessible to me.

B. Isevis, Leydig, seems simply a smooth condition of other spe-
cies. Whether B. curvirostris, Leydig, is or is not valid must, so far
as I am concerned, remain at present doubtful.

Genus Bosmina.

A. Shell extending into a spine behind.

(a) Antennte curved outward.

1. Bosmiiia cornuta, ]urine.

(b) Antenuffi not curved outward,

I. Shell reticulated, at least in part.
t Plagellum midway between e3'e and the sensory setae of antennae.

2. Bosmina longirostris, Mueller.
ft Flagellum nearer eye.

3. Bosmina tnaritima, P. E. Mueller.

4. Bosmina longispina, Leydig, (B, brevirostris'')
II. Shell striate.

t Antennules long.

66 TWELFTH ANNUAL REPORT.

5. Eosmina striata , Derrick .
tt Antennnles short.

* Rostium long.

6. liosmina lacmtris, Sars.
** Rostrum short.

7. Bosmina obtvsi7-ostrw, SaTB. (B. nitida, Sare?)

B. Shell not spiued behind.

(a) Shell strongly arched above.

8. BosminalilJJ6borgii,Sars, (B. diaphana?)

(b) Shell moderately curved above.

9. Bosmina microps, P. E. Mueller.

Coucerninsj the identification of Bosmina longispina, Leydig,
with B. brevirostris, P. E. Mueller, it must be said that the bow is
drawn at a venture, for Mueller, in his paper on the Cladocera of
Swiss Lakes, in a fit of absent-mindedness refers to B. lacustris, P.
E. Mueller, citing p. 149 of Danmark's Cladocera. On ttie page in
question are descriptions of B. maritima and B. brevirostris of which
the latter is probably the one meant. Sars' B. lacustris seems quite
difiierent, being strongly marked by longitudinal lines, while Leydig
says of B, longispina "shell striped and small reticulate," and P. E.
Mueller says in B. brevirostris the shell is "utydeligt reticuleret"
i. e. indistinctly reticulate.

The three species so far identified in America are B. longirostris,
of which a figure is given (plate J, fig. 2,) B. cornuta and B. striata,
which may possibly be yet identified with one of the European spe-
cies, though it seems improbable. I have also seen a species like
L?ydig's B. lasvis, but considered it a smooth variety of B, longi-
rostris.

FAMILY LYNCODAPHNID^, Sars, 1861; Herrick, 1881.

This is a rather small family with seven genera of minute ani-
mals Avhich are abundant only in summer. Many and, indeed,
most oi the species are among the rarer of fresh-water crustaceans
of this group, and a few are among the rarities which only now and
then reward the collector. This family undoubtedly is the link
connecting the Daphnidse with the Lynceidse, relationships to which
are expressed by Macrothrix, on the one hand, and Lyncodaphnia,
on the other.

The rank of this group as a family must be, of course, a matter
largely of opinion. Sars was the first to adopt this view, sustained
by certain curious transition forms leading toward Ljmceidie. Later
writers seem never to have found these genera and the group was

STATE GEOLOGIST. 67

again included with the Daphnida3. The writer, upon the dis-
covery of the Lyncodaphnia, was forced to regard this group as of
equivalent grade with the above mentioned families and again pro-
posed the family name Lyncodaphnidfe. ^

The genus Ilyocryptus is a little one side the normal course of
the family and seems related to the lynceid genus Leydigia.

The waters of the northern United States are very rich in
members of this family.

The aberrant family Bosminidas finds its only connection with
other Cladocera through this group by means of the remarkable
Macrothrix (?) pauper; and here it is only vaguely hinted at in the
elongated antennules and angled lower margin of shell, as well as
the presence of certain bodies near the base of the antennules. It
has been affirmed that none of the Lyncodaphnidse have an ephip-
pium, i. e. the saddle-shaped thickening of the shell walls to in-
clude and protect the winter eggs; but I have discovered it in the
case of Macrothrix tenuicornis, Kurz, and presume it may occur
exceptionally in others. Kurz says that Ilyocryptus has no moult
proper, but this probably refers only to the European I. sordidus.
The American species differs from the generic description given by
Kurz, and may be different in this respect also.

In this family the regularity in the disposition of the seise on
the antennae is broken and the fringing of these hairs serves the
purpose of specific distinction. The antennules are always long
and frequently differ considerably in the sexes. The pigment fleck
is always present (Kurz is in error in denying its existence in La-
thonura). In many forms there is no free posterior margin of the
valves, while the lower is generally thickly beset with movable
spines. The Lyncodaphnidaj will be distinguished from Cerio-
daphnia, which they resemble, by their motion, which is a succession
of quick bounds, while the broader Ceriodaphnise hobble along as
though heavily weighted by the enormous mass of eggs with which
they are generally laden. The abdomen is usually short and the
anus is behind the terminal claws, but in Ilyocryptus the claws are
long and spined at the base. In the American I. spinifer the anal
opening is elevated to a point nearly underneath the stylets, and
there is a rudimentary anal caecum as in Lynceids.

The males have the opening of the vasa deterentia in front of
the cIp.ws, which may be absent; the antennules are also modified,
being longer and curved. In Lathonura the abdomen is elongated

1 Notes on Some Minnesota Cladocera. 1881.

68

TWELFTH ANNUAL REPORT.

posteriorly tijl it begins to suggest a transition to Polyphemus.
The known genera and their distribution is as indicated below.

Half of the known species are found in America; one sixth being
peculiar to it.

GENEKA.

Total
n urn bar

of
species.

Europ-
eau.

Also
Amer-
ican.

Only in
America

Total
Amer-
ican.

). Macrotlirix

2 Lathomira

3

3

2
1

1

3
X

3. Drepanothrix

4. Streblocercus

5. Acantholeberis

6. Of ry oxiis

i "

1

7. LYDcodaphnia ?

I

1

1

8. Ilyocryptus

2

1

Totals

13

10

1 4

3

I. Genus Macrothrix, Baird.

Body oval, pointed behind; head broad; antenna3 of first pair
long, nearly straight, beset with spines, olfactory threads terminal ;
swimming antennae large and powerful, propelling the animal
by bounds; three-jointed ramus with a greatly elongated seta which
is thorned and jointed; labrura with the basal joint enlarged,
resembling that of Lynceids; first foot with a hook in both sexes;
last foot with a long process (respiratory body); abdomen short;
claws short; caudal stylets often with a bush of hairs at tip. The
intestine is straight and without caeca in front or behind.

The first one to observe a member of this genus, apparently, was
0. F. Mueller whose Daphnia curvirostris is usually referred to
Macrothrix laticornis.

The name Echinisca was proposed by Lievin, but Macrothrix was
applied by Baird in 1843. Four species are known, three of which
occur in America and without doubt the fourth will ultimately be
found. No males of this genus were known till 1877 when the
male of M. laticornis was described and figured. ^ Nearly two years
later the male of M. rosea was described from Wisconsin by E. A>
Birge. Descriptions of the male of Lathonura are also given in
both the above mentioned sources.

Sp. 1. Macrothrix laticornis, Jurine.
(Plate C. Figs. 7, 8 and 9.)

Daphnia eurviro8tris(,f), jviueller.
Monocuhis laticornis, jxjkine.
Lynceus laticornis, desmabest.

1 Gruber und Weismann, Ueber einige neue oder nnvoUkommen gekannte Daph
niden. Freiburg.

STATE GEOLOGIST. 69

31 acrothrix laticornis, BX1R.D, Ann. Ma,g. Nat. Hist.

^icanthocercus currirostris {/), schoedler, Ericlis. Arcliiv, 1846.

Dapfinia curvirostris, fischer.

Mncrothrix laticornis, lillteborg, LErDiG, baird, p, e. muei.ler, fric, kurz,
SARS, LUTZ, CLAu.s (Die Sclialendruse d. Uaplinlen), norman
and BRADY (Monogr. Brit, lintom.), gruber and weismanx,
weismann, (Beitrage zur Natuvgeschiclite d. Dapb.)

This is the commonest European species and is the type of the
genus, showing its rather conservative position by the broad tip of
the antenna which is a feature exhibited by embryos and young of
other species. The shell has a warty surface and is toothed above,
while the lower margins are fringed with long unequal spines in
groups of threes or fours.

The form is roundish with a blunt posterior angle, the ventral
margin being regularly curved. The antennules are short and en-
larged at the end. The form is an irregular pentagon; a pair of
slender spines sits at the angle near the base.

The swimming antennee with the seta on the first joint of 3-
jointed ramus very long. Post-abdomen truncate at the end, short,
posterior margin beset with series of bristles.

Length of male 0.5 — 0.6 mm,, of female 0.4 mm.

This is the smallest of the genus and will undoubtedly be found
in America.

Sp. 2. Macrotlirix rcsea, Jurine.

(Plate C. Fi^s. 5, 6, 11, and 13.)

Monoculus roseus, jorine.

Lunceus roseus, desmarest.

Daphnia rosea, m. edwards, jurrell.

Echinisca rosea, lievin.

Macrothrix rosea, baird, ltlljeborg, p. e. mdeller, bibge.

The body is sub-oval, terminating behind in an acute angle; the
lower margin is less conspicuously spined than the last or the
following; the antennae are but slightly dilated at the end and
nearly straight. The longest seta of the antennae is longer than
in the last, reaching beyond the tips of the terminal setae; abdo-
men more slender, sinuate in front, beset with short hairs. .

Length 0.6 mm, male 0.3 mm. The male has no claws on the end
of the post-abdomen, and the antennules are curved and elongated.
Figures 5 and 13 are copied from Birge.

70 TWELFTH ANNUAL REPORT,

Sp. 3. Macrotlirix tenuicoruis, Kuiv.

(Plate C. Figs. 1, 1 a, 2, 3, and 12.)
(See Notes on Cladocera of Minnesota, p. 245.)

The body is oval, produced posteriorly in'a sharp point; the ab-
domen is strongly arched, while the upper outline'of the head is a
regular curve or slightly extended in front of the eye; the anten-
nules are long, nearly straight and a very little narrowed toward
the end, just in front of which is a series of short teeth; there is no
lateral spine, but a strong terminal one in addition to the sensory
filaments; the pigment spot is large, the eye small and the lobu&
opticus well separated from the ganglion; the antennas have a very
powerful basal joint; the elongated seta is very stout and densely
spiny, with a tooth at its flexure; two of the terminal setse are
spiny, for the basal half; the valves are beset with very long spines
in sets of three each, all having different positions; the abdomen is-
nearly as in M. rosea, but the posterior margin has a series of long
sharp teeth; the mandibles are nearly completely exposed by the-
arched anterior margin of the valves.

The labrum, in this species, is an odd link between that of the
Daphnidas and Lynceidse. The basal segment is greatly enlarged
and is sub-triangular in outline, with a movable lip attached to the
inner free face; the typical daphnoid structure is preserved, but the
enlarged salient angle of the basal portion shows how the transi-
tion to the great triangular labrum of Alona, etc., is made. In
young specimens the head is proportionately larger, the antennules
are broader at the tip, and the dorsal outline is less convex; the
marginal spines of the valves are also proportionally larger, as are
the appendages of the first and last pairs of feet. This is one of the
largest species of the genus, 0.75 mm. being the length. Thia
is very close to M. rosea but seems distinct.

This form is quite common about Minneapolis, Minn., but is not
yet noted elsewhere in America.

Sp. 4. Macrothrix pauper, Herrick.

(Plate C. Fig. 4.)

This species is described from a single specimen from L. Minne-
tonka, and I can add nothing to the very meager notice given
then. 1

1 Notes on some Minnesota Cladocefa. 1831. C. L. Herrick.

STATE GEOLOGIST. 71

The body is broad and very narrow, the lower outline is angled
and nearly unarmed; the pigment fleck and eye are small and ap-
proximated; antennules very long and curved backward and out-
ward; abdomen short, ciliate below; claws short, ciliated. This
female had a full complement of eggs but the antennae resemble
those of a male. This is unusually interesting and should be redis-
covered and studied; for there seems to be some affinity between
this species and Bosmina, and it is probable that it requires to be
distinguished generically from Macrothrix.

II. Genus Lathonura, Lilljeborg.

The form is oval ; the head is curved more than in Macrothrix
and the shell is moro obtuse behind, sinuate below where it is beset
with short spines anteriorly; first antenoaa long, straight; second
antennge with five setae on each ramus; only four pairs of feet ap-
parent; abdomen short, prolonged upward to the insertion of the
caudal stylets; male similar but smaller.

Sp 1. liathonura rectirostris, 0. F. Mueller.

(Plate D.)

Haphnia rectirostris, o. v. mukllek.

PasitUea rcctirostria, koch, Deutsch land's Krust., etc.

Daphniahracliyura,zxDDACR,Syn. Cruse, prussicorum. lievin. Die Branch, d.

Danziger Gearend.
Daplmia mystacina, fischek, St. Petersb. Branclii'ip,
Lathonura rectirostris. lilljeborg, De Crust, ex oid. tiib.
Pasithea rectrirostris, leydig, Naturg. d. Daph.
Lathonura rectirostris, yoHMAia anH bkady, Alonogr. Brit. Ent. ; p. e. muelleb,

Danmarli's Ciadocera.
Lathonura spinosa, schoedleu, Biaiicliiop. d. Uinp;. v. Berlin.
Pasitlica rectirostris, GRUBER and weisjiann, Ueber einige neue od. unvolll<. ge-

kannte Dapli.
Lathonura rectirostris, birge, Notes on Cladocerii. herrick, Notes on Minnesota

Ciadocera.

The only species of the genus is distributed probably over the
entire northern temperate zone. It has been found in America at
Cambridge, Mass., and in the vicinity of Minneapolis, at both of
which places it is very rare.

The form is a rather quadrangular oval, the head being strongly
arched to the beak which is much farther posterior ,than in Macro-
thrix, in this respect resembling the Daphnidae; the eye occupies
the center of the lower part of the head margin, and is of moderate
size; the pigment fleck is near the base of the antennules and well
removed from the eye; the antennae are straight and long, with a

72 TWELFTH ANNUAL REPORT.

sensory bristle near the base in front and two bristles a third from
the end; the second antenna are furnished with a powerful basal
joint, while each of the main subdivisions of the rami has its bristle,
which are nearly equal; two of the terminal setae are toothed for
the basal half and pectinate distally, but the others are feathered
throughout; the four-jointed ramus has a spine on the second joint
and a longer one at the end, and all the joints of both rami are orna-
mented with triple series of spines; the maxillffi are three-spined at
the end and are in almost constant motion; the first pairs of feet
have curious comb-like bunches on some of the setge; the abdomen
is very short and terminates in inconspicuous teeth, the posterior
part of the abdomen being ornamented with teeth flattened longi-
tudinally so as to look like spines from the side; the last foot is
simple but bears a large appendage; the posterior third of the shell
is fringed by extremely minute spines, but anteriorly by lanceolate
stiff spines flattened longitudinally like the spines of the abdomen;
the caudal setffi are seated on a high prominence of the abdomen,
and are fringed along their whole length, not merely at the end.
The female is 1 mm. long, the male 0.5 — 0.6 mm., in which sex the
antennules have more numerous lateral bristles, the first foot has
a claw and the back is less elevated. The semen bodies are irre-
gularly round with small nuclei.

III. Genus Streblocercus, Sars.

In form like Macrothrix laticornis, head terminating in a long
rostrum bearing the long, twisted antennules. Antennules very
large, curved backward and outward. Head not separated by a
destinct depression from the body, very high, slightly arched above,
abrubtly curved below with spines upon the margins. The anten-
nae are large; four-jointed ramus much the longer, with four setae.
Labrum with a large process. Post-abdomen as in Macrothrix lati-
cornis. Eye near the beak ; pigment fleck small, below it at the
base of the antennules. Length .33 mm. S. minutus is the only
species.

Our Macrothrix pauper seems a near approach to this genus;
both have a strong spine or claw on the first foot which projects
beyond the shell, but there are many diSerences. M. pauper is
1 mm. long.

STATE GEOLOGIST. 73

IV. Genus Drepanothrix, Sars.

The head not separated from the valves by a depression; forniees
moderate; rostrum rather acute, distant from the anterior edge of
the valves. The form is subrotund; reticulate, with the margins of
shell fringed below by long movable spines; pigment fleck present;
swimming antennse with three ciliated setse on the 4-jointed ra-
mus, the 3-jointed ramus with its basal joint armed with an un-
jointed, strong, spinous seta and four ciliated setse on the remain-
ing joints. The post-abdomen is broad. The male has longer an-
tenna? and a hook on the first foot.

Sp. 1. Drepanothrix clentata, Euren.

(Plate C. Fig. 14.)

Acantholeberis dentata, edrek.
Drcjxinothrix setigera, sabs.
Drepanothrix Jmmata, saks.

This animal is only 0.5 mm. in length. The antennules are
laterally curved in the middle and ornamented with notches on the
margins; the pigment fleck is quadrate and rather large; the post-
abdomen is truncate at the end, convex behind and ornamented
with a series of small spines. Only found in Scandinavia as yet.

V. Genus Acantholeberis, Lilljeborg.

Head separated by a depression from the body, with forniees
above the base of the swimming antennee; rostrum erect, rather
acute; shell oblong, truncate behind, eiliate below with long setae;
macula present; antennules rather long, movable, sensory setge
terminal, bifld at the apex.

The tri-articulate ramus has a long spiny seta on the basal joint:
feet six pairs; no abdominal process; post-abdomen wide, large; in-
testine without cffica.

Sp. 1. Acantholeberis ciirvirosti'is, Mueller.

Baplinia curvirostrit>, o. f. mueller.
Acanthocercns rigidus, schoedler, lievin.
Acantholeberis curvirostrh, lilljebokg, p. e. moeli^er.

This species of a genus approximating the Lynceids has not yet
been fjund in America but is to be expected.

The abdomen is rounded toward the end and spiny posteriorly;
the terminal claws are furnished with two strong teeth at the base,

74 TWELFTH ANNUAL REPORT.

followed by a series of fringing bristles. The length, according to
Mueller, is 1.5 mm. This is a rare form in Europe.

VI. Genus Ofryoxus, Sars.

The single species constituting this genus seems to have been
seen by no writer save Sars. At the time ray previous paper on
Cladocera was published, Sars' description seemed not to apply ta
the form called Lyncodaphnia. Since then several stages in the
growth of Lyncodaphnia have been encountered, which so far agree
with what is said of Ofryoxus gracilis that it is doubted if the two
forms are not identical.

VII. Genus Lyncodaphnia, Herrick.

(Plate B. Figs. 12, 15; Plate Bi, Fij^:^. 1, 3.)

Body elongated, somewhat rectangular as seen from the side,
greatest width and hight of shell a little posterior to the heart;
head separated by a depression from the body, truncate below;
antenna? and antennules much as in Macrothrix; -i-jointed ramus
of antennae with no lateral seta?; eye small, pigment fleck present;
intestine twice convoluted, expanded posteriorly, with anterior but
no posterior cgeca, opening near the *' heel " of the post-abdomen:
post-abdomen large, triangular; terminal claws long, rather straight,,
with two accessory spines at the base.

The species upon which this genus was founded ^ occurs in
August and September in the larger lakes of Minnesota.

Lyncodaphnia is, as was suggested, a curious transition form
linking the Daphnidae with the Lynceidae.

A farther study of the genus shows that, in some respects, it is
more closely allied to both groups than before suspected. The habit
and appearance in the water reminds us of Simocephalu?, a re-
semblance which an occasional spot of pink or blue color hightens.

L. macrothroides not only has the disc-like last foot colored but
the swimming antennae are banded with purple as in Simocepha-
lus rostratus, Her., and S. americanus, Birge. The intestine has
anterior caeca, which is not the case in lynceids nor, indeed, in
other Lyncodaphnidae.

The four-jointed ramus of the antennae approaches Lynceidae in
the absence of a lateral seta, but the other ramus is as in Macro-
thrix. The convolution of the intestine, the form of the post-
abdomen and the situation of the anus, are all of a strictly lynceid

1 Notes on Minnesota Cladocera, p. 247.

STATE GEOLOGIST. T5

type; moreover the flattened appendage of the last foot is like that
of Eurycercus.

Even ia the form of the shell there is a combination of charac-
ters; the anterior part of the shell has the form peculiar to Lynco-
daphnidae; but posteriorly it again expands and becomes truncate be-
hind; the form in the adult is not unlike that of some Lynceida?,
but the young has a long spine posteriorly exactly like the spine
of Daphnia. The latter fact is very instructive, for it indicates that
the theory proposed (Am. Naturalist, 1882, p. 815) to explain the
origin of this appendage is probably the correct one. Professor
Leuckart suggested that this spine was a balancing rod intended
to keep the proper equipoise over the center of gravity; but it is
difficult to see why these loug-bodied forms, in which the greater
part of the weight lies "abaft" of the pivotal point — the base of the
antenuffi— should be thus provided while the shorter forms are not.
We conceive that it is an apparatus for effecting the moult of the
inner lining of the brood cavity of long-bodied and tender-shelled
animals such as Daphnia and the present genus. The great develop-
ment of the hpad in the crested Daphnidee may undoubtedly be ex-
plained upon Prof. Leuckart's theory,

Sp. 1. Lyucoclaplinia niacrotliroides, Herrick.

(Perhaps = Ofryoxus gracilis, Sars.)
Notes on Cladoccra of Minn., p. 247.

Sub-rectangular, greatly elongated, truncate behind, with a
slight spine above; head and eye small, fornix moderate, beak
truncate; antennules rather long, slightly curved, tapering a little
toward the end, whence spring three lanceolate spines and several
sensory filaments, five stout spines behind, above the middle, and
several more slender ones; swimming antennae very long, terminal
seta3 smooth to the joint; labrum as in Daphnia; mandible attached
behind a salient angle of the front margin of the shell; no ab-
dominal processes; post-abdomen broad above, triangular; terminal
claws pectinate, furnished with one very large toothed accessory
spine and a smaller one; the firstfoot has a hook ; the last foot
consists of a large oval plate which bears posteriorly the ordinary
branchial coil, here shaped like a thumb and forefinger. The young
is of a different shape and bears a long spine. The male is unknown.

76 TWELFTH ANNUAL REPORT.

VIII. Genus Ilyocryptus.

Form compact, short; head short, triangular, with large foruices
forming a roof over the head; the posterior margin of shell nearly as
long as the inferior; lower angle a broad curve; antennules two-
jointed, basal joint very short, second joint straight, rather long;
setpe terminal, but one seta near the base; the four-jointed ramus
of the antenna with but three (terminal) setae; six pairs of feet, last
pair rudimentary; tail large, as in Lyncodaphnia, anus elevated;
intestine straight, without caeca, but an expansion near the rectum
sometimes simulates one; the margin of the shell is bordered with
long spines, which may be branched or simply pectinate. There is
often, perhaps generally, a failure to entirely remove the moulted
shell; when this occurs, the newly-formed shell from each moult
remains under the older ones till the animal seems to be wearing
six or more overcoats, and the spaces so formed become filled with
algae and filth till the animal is no longer able to swim. P. E.
Mueller and Kurz, who seem to have seen only I. sordidus agree
that Ilyocryptus can not swim, but poles along in the mud on the
bottom by means of antennae and abdomen; our I. spinifer, on the
other hand, swims freely till loaded up with old clothes and filth.

This genus is also closely allied with the Lynceidae.

Sp. 1. Ilyocryptus sordidiis, Lievin.

(Plate C. Fiffs. 15, 16, 17.)

Acanthoeernis sordidus, lievin, leydig.

Ilyocryptus soi^didu^, sars, nokmann, p. e. mueller, kurz.

Body higher than long; head small, terminating anteriorly in
almost a right angle; posterior part of the shell margins covered
with branching, thorny spines; antennules cylindrical; antennae
short: four-jointed rami with no lateral setas; post-abdomen large,
broad; terminal claws with two spines at the base; anas in the
middle of the posterior margin, which is very heavily armed with
spines; a hairy abdominal process is present according to Kurz.

There are no anterior cgeca (my statement that P. E. Mueller
described such ca3ca was an error; see Notes on Cladocera of Minn.,
p. 246).

STATE GEOLOGIST.

77

Sp. 2. Ilyocryptus spinifer, Herrick.
(Plate C. Figs. 18—19.)

Usually longer than high; head rounded, almost exactly like T.
sordidus, but the form of the post-abdomen differs a little in the
higher situation of the anus and the great elongation of four or
five of the lower spines of the posterior margins; the margins of
the shell are beset with pectinate setae which do not branch. The
nearest approach to branching set^ yet seen are figured on plate C,
fig. 18 a; this consists in the outgrowth of a spine from near the
base, and such setae are found only on part of the posterior margin.

It seems that our form is rather close to I. sordidus though
clearly distinct.

This species occurs in many of our lakes, and is found most fre-
quent in late summer.

Sp. 3. Ilyocryptus acutlfrons, Sars.

This species is only mentioned in the appendix to the paper of
Sars on the Cladocera from the vicinity of Christiania. The follow-
ing is a condensation of the description.

Head large, acute in front. Shell truncate behind, with shorter
setae behind than below. Antennules shorter and thicker than in
I. sordidus. Antennae long and robust. Abdomen with a short,
obtuse process. Post-abdomen shorter than in I. sordidus, posterior
margin continuous, anus terminal; caudal claws straight, very long,
with two minute basal spines. Figment fleck almost touching the
eye. Length less than in I. sordidus.

This species seems in some respects more like a true lyncodaph-
nid than either ot the other species. It is doubtful if it belongs
here.

FAMILY LYNCEIDiE.

GENEEA.

1. Eurycercus

2. Acroperus

3. Camptoceicus . .

4. Alonopsis

5. Leydigia

6. Graptoleberis...

7. Crepidocercus . .

8. Alona

9. Alonella

10. Pleuioxus

11. Harporhynchus
2. Cliydoius ,

13. Anchistropus

14. Monospilus

Totals

Number

of

known

species.

1

2

6

3

2

2

1
21

5
14

8(?)

1

1

G8

Europ-
ean.

14

6(?)

1

1

50

Also in
America

In

America

only.

20

16

Total
Amer-
ican.

1
1

2

2
2
1

1
13

2

7

3

K?)
1

37

78 TWELFTH ANNUAL REPORT.

Out of the fourteen genera, two (or perhaps only one) are not
yet known from America, while one is restricted to it. The Amer-
ican species, 45 per cent of which are new, aggregate 72 per cent
of the European. 54 per cent of all the known species are Amer-
ican, and most of these have been found within a range of ten miles
of Minneapolis. It is probable that the number of species peculiar
to America is too high proportionately rather than the reverse, and
the comparatively high per cent of new species is due to an actual
larger fauna in the New World, Avhile many Old World species
remain to be identified. A few of the European species are very
likely synonyms, permitting farther reduction.

This family, which is numerically the largest among the Clado-
cera, is, in the main, well limited, though there are transitions to-
ward the Lyncodaphnidae, which are quite direct. The genera
Lyncodaphnia, Ofryoxus and Ilyocryptus lead toward the Lynceid^
unmistakably. Most of the members of this family are small, com-
paratively few exceeding one millimeter in length. The head is
covered with an arched shield, which frequently passes with no in-
dentation into the shell of the body. This head-covering generally
extends forward and downward to form more or less of a sharp
angle in front, while in several genera it is simply rounded in front.
It, in either case, arches over the more fleshy lower side of the head
from which hang the two short antennules and the labrum, while
the strong two-branched antenna spring from well up under its
posterior expansion. The rounded sides of this shield, which pro-
tect the insertion of the antennge, are called the fornices. Above
the insertion of antennules is a dark fleck lying near or on the
lower angle of the brain; this is the larval or nauplius eye, which
is the first to appear in all these small Crustacea. This macula
nigra is not infrequently as large as the eye itself, * or even larger,
and in one genus it is the only visual organ. The antennules
are small and bear on the end several sensory filaments as well as
a lateral flagellum. The antennules of the male diflfer very little
from those of the female. The labrum is furnished with a process,
which is triangular or semicircular and is usually larger than the
terminal portion. The mandibles are as in Daphnidae but usually
shorter. Maxillee are often conspicuous, but the first pair of feet
serve, by a slight alteration at the base, the same purpose. There
is rarely an indication of the sixth pair of feet, and the antennae
have both rami three-jointed. The terminal part of the body, or

* The name "Lynceus"' is derived from that of the son of Aphareus who was famous
for the sharpness of his vision.

STATE GEOLOGIST. 79

post-abtloraen, is usually enlarged, aud the anal opening is near its
base; the armature is usually considerable. The form of the post-
abdomen is one of the best criteria for distinguishing genera aud
species — a process often attended with much difficuUy.

The shell is of various forms, frequently beautifully sculptured.
The number of eggs produced at onetime is limited, and the winter
€ggs are very often laid in the brood-cavity with no preparation of
the shell previous to it, in other words, the ephippium may be ab-
sent. On the other hand, sometimes the shell is considerably modi-
fied, and generally there is a deposit of dark pigment in the upper
part of the shell. The males are very rare and until recently few
were known. The diligence of Kurz has added a great many, and
we now have a fair idea of the sexual variations. These consist
usually in a narrower body and shorter beak, in a strong hook of
€hitin on the first foot and certain modifications of the post-abdo-
men. The hook mentioned is simply an enlargement of one of the
terminal bristles of the foot, and serves to fasten the animal to the
shell of the female. In one American species of Pleuroxus we find
an approach to this structure in the female — an interesting example
of inheritance of sexual peculiarities across the sexes. The altera-
tions in the form of the post-abdomen consist in a narrowing or
excavation of that organ to permit its introduction into the brood-
cavity, and in some forms (Chydorus) this change can only be
understood by observing the form of the shell of the female about
to produce winter eggs. In general, as in other Cladncera, males
are found only at the period when the females are sexually perfect.
The ordinary method of reproduction is by virgin-bearing or par-
thenogenesis. In some cases it would seem from Weismann's ob-
servations that the sexual method occurs only incidentally. The
orifice of the male organs is between, or anterior to, the terminal
claws of the post-abdomen (Eurycercus alone excepted). The males
are usually but not always smaller. Plate E gives views of typical
Lynceidas Fig. 1 is particularly instructive, for in it the details
which can be usually made out in the living object are represented.
The following points may be especially noticed. The large size of
the pigment fleck, the large antennules (A^), the keel of the labrum
(Lb.), the peculiar modification of the first pair of feet to assist the
maxillae (not shown) which are exceedingly small, the largely de-
veloped anal gland (A. g.), the form and muscular mechanism of
the abdomen, which, however, is better illustrated by fig. 10 of the
same plate. Fig. 1 contains an embryo seen from the side with the
partially developed limb. Fig. 3 shows the appearance of a differ-

80 TWELFTH ANNUAL REPORT.

ent embryo from below and in an earlier stage. Fig. 2 illustrates
the relation of the brain to the eye and the very small optic gang-
lion. Fig. 9 of plate G gives details of the feet in another species,
and the modifications seen in the male of the same species are suffi-
ciently shown in fig. 1 of the same plate, which also well illustrates
the various sculpture of the shell displayed by this group. Figures
4 and 9 of plate F show curious modifications of the post-abdomeu
of the male, and fig. 7 exhibits the structural peculiarity of sexually
perfect females which is correlated with it or, perhaps we may say,
occasions it.

SUB-FAMILY 1.— EURYCERCIN^.

A single species constitutes the sub-family, and it will be necess-
ary to point out only those points which are distinctive.

The Eurycercinas differ from the true Lynceidffi and approach the
Lyncodaphnidse in having the digestive tract not coiled, with two
Cceca in front and the anus at the end of the post-abdomen. Many
eggs are produced at once. The male opening is at the base of the
abdomen, as in Sididge. The general habitus is, however, lynceid.
The males appear in autumn or when, by the gradual drying up of
the water or other causes, the continued existence of the animals is
threatened.

I. Genus Eurycercus, Baird.
Characters of the sub-family.

Eurycercus laniellatiis, 0. F. Mueller.

(Plate H. Figs. 5-6.)

Lynceuslamellalus, MUELLER, EDWARDS, KOCH, ZADDACH, LTEVIN, LEYDIG. ZENKER
Eurycercus lamellatus, BAIRD, LILL.IEBORG, SCHOEDLER, P. E. MUELLER, KURZ, BIRGE,
HERRICK.

Eurycercus laticaudahis, FISCHER, SCHOEDLER.

A gigantic lynceid, reaching the dimension of 3 mm. The figure
of the male .given will sufficiently illustrate the general form. The
abdomen is broad and armed behind with a dense row of saw-teeth.
The eye is larger than the rather small pigment fleck, and the in-
testine is bent upon itself but not coiled. The last foot is found in
few other Lynceidee. Acroperus has the same, and Pleuroxus uui-
dens also has a rudimentary sixth foot.

STATE GEOLOGIST. 81

SUB-FAMILY II.— LYNCEINiE.

Intestine coiled; anus near the end of the post-abdomen; open-
ing of vas deferens nearly terminal. There are no anterior ceeca
but usually a single anal diverticle of the intestine. Rarely or never
more than two embryos produced at once.

Series A.

Head or dorsal line keeled or ridged ; abdomen long ; shell marked witli ^(agonal
striffi. This section is proposed for the old genera Camptocereus, Acroperus and Alo-
Hopsis, which seem to form a natural group though passing directly into Al ma.

II. — Genus Camptocercus {> Camptocereus, Baird).

This easily recognizable genus contains two groups, each with
several nominal species, which are distinguished mainly by the
width of the post-abdomen. In both the shell is elongated, more
or less quadrangular, longitudinally striate, armed behind with one
to four minute teeth. The head and back are keeled and the former
strongly arched. The antennules rarely extend beyond the beak
and are commonly curved laterally. The eye is proportionately
small. The post-abdomen is long and furnished with a lateral row
of scales. The terminal claws have a single basal spine and are
serrate. There is an ephippium, and the male opening is in front
of the terminal claws.

Sub-genus 1. — Acroperus, Baird.

Post-abdomen broad, margins parallel; anal teeth very minute
lateral scales large and usurping their place. Antennge with eight
setae (§n). Three species are described, one of which is very abund-
ant in Minnesota.

Sp. 1 . Acroperus leiicocepliahis, Koch.
(Plate E, Fig. 5. Plate I, Fig. 9.)

Lynceus leucocephalus, KOCH, FISCHER.

Acroperus harpw, BAIKD.

Acroperus leucocephalus, SCHOEDLER, P. E. MUELLER, KURZ.

Acroperus sp., HERRICK.

Acroperus striatus.JVRiyE, M.EDWARDS, LiEviN, lilljkborg, leydig, etc., se'

to belong here, but I am able to add nothing to the eluci-
dation of the puzzle.

Body rounded above, angled behind; head moderately arched and
carinated. Lower margin of the shell pectinate, terminating in
6

82 TWELFTH ANNUAL REPORT.

two teeth. The antennge are long and when reflexed the setae
reach nearly to the posterior margin of the shell. The posterior
angle is not always as prominent as shown in fig. 5.

Sp. a. Acroperus angustatus, Sars.

(Plate I. Fig. 10.)

Acroperus angustalus, V. E. MUELLER, KUKZ.

This species is distinguished from the former by the head, which
is higher and very strongly arched. The dorsal contour is nearly
straight. The antennae are shorter. The form of the post-abdomen
of the male is less different from that of the female than in the
above. The length of both species is about 0.7 mm.

The American form figured in fig. 5 of plate E differs from both
the above slightly. The head is carinated and incurved almost as
in C. angustatus; the antennae fall a little short of reaching the
posterior margin of the too low and oblong shell; there is an ob-
vious depression between the head and body. However, in the main
there is close agreement with C. leucocephalus, to which it has been
previously referred. There is always a rudiment of an additional
pair of feet.

A. cavirosfris. P. E. Mueller, is not known in the female sex.
The male has a twisted caudal claw.

Sub-genus 2. — Camptocercus, Baird.

Although the general form is similar to the last section, the body
is usually longer; the post-abdomen narrows toward the end; the
anal teeth exceed the lateral row; the antenuffi have usually but
seven setae (jtf)-

The species enumerated are so closely related as almost to baffle
definition.

Key to the Sub-genus Camptocercus (verus).
Beak pointed.

(a) Head depressed.

I. Pigment fleck larger than the eye.

1. C. biserratus, SCHOEDLEB.

II. Pigment fleck smaller than the eye.

2. C. macrurus, O. F. MUELLER.

(b) Head directed forward.

3. C. rectirostris, SCHOEDLER.

Beak truncate below.

4. C. laiirostris, KURZ.

STATE GEOLOGIST. 83

Beak cleft below or with a forward projection.

(a) Antennules shorter than the beak.

5. C. lilljeborgii, 8CH0EDLEK.

(b) Antennules longer than the beak.

6. C. roUtiidus, HEBKICK.

Sp. 1. Camptocercus biserratus, Schoedler.

{Plate I. Fig. 4.)

Is very nearly related to the next, from which it is distinguished
chiefly by the fact that the pigment fleck is larger than the eye.
Schoedler overlooked the fact that in C. macrurus there is a lateral
line of scales on the abdomen, and relied upon that character to
distinguish this form. (Schoedler says that the pigment fleck in C.
macrurus is smaller than the eye, P. E. Mueller says they are nearly
equal, while in our specimens they are much smaller or nearly
€qual.) If much variability is found, Schoedler's species seems to rest
on a slender basis. The basal spine of the claw, however, seems to
be peculiar in sitting on a distinct prominence.

Sp. 2. Camptocercus niacriinis, Mueller.
(Plate E. Fig. 10.)

Lynceus macnirus, LILLJEBORG, SCHOEDLER, P. E. MUELLER, KUKZ, BIRGE, HERRICK.

This universally distributed species occurs in our larger bodies
of water and is not rare, though hardly abundant.

The body is long and nearly rectangular; the head strongly
arched and keeled. The keel of the head is extended down the
whole dorsal line. The dorsal line is moderately curved, while the
shell is but slightly excavated below. The head extends into a
blunt beak looking downward; the direction of the head is some-
what variable (from vertical to an angle of about 30°). The eye is
much larger than the pigment fleck; the antennules are shorter
than the beak, and have one elongated terminal seta. The post-
abdomen is very long and has numerous anal teeth as well as a
lateral row of scales. The basal spine of the claws is large and ser-
rate, the claw itself being nearly straight and armed with an in-
creasing series of spines to beyond the middle. The lateral scales
of the post-abdomen are inconspicuous. The shell gland is long.
The antennules reach to almost the end of the beak, are curved and
bear a lateral flagellum. The first foot of the female has a sort of
hook (branchial sac?). The labrum is armed with teeth on the
posterior face of the triangular process. The intestine is very
trongly, almost twice coiled. The lower margins of the values are

84 TWELFTH ANNUAL KEPORT.

feebly spined for three-fourths their length, and armed with from
one to four teeth at the angle. Length O.S mm. to 1.0 mm.

Sp. 3. Camptocercus rectirostris, Schoedler.
(Plate I. Figs. 1—3.)

Camptocercus rectirostris, SCHOBDLBB, P. E. MUELLER, KURZ.

Distinguished from the above, which it closely resembles, by the
form of the head, which is less rounded and directed anteriorly. It
hardly exceeds half the hight of the body. The beak is sharp, I
am not sure that Weismann's figures (1. c, plate XI, figures 13 and
14) really belong to this species, for the drawing of the post-abdo-
mea does not agree with that of P. E. Mueller fully. Outline copies
of the former are given in plate I, figs. 1 and 2. The male has a
hook upon the first foot. Not yet recognized in America.

Sp. 4. Camptocercus latirostris, Kurz.
(Plate I. Figs. 5—6.)

C. liUjeborgii, P. E. MDELLEK (?).

Closely allied to the next, but distinguished by the position of
the head, which is a little less depressed, and, especially, by the
truncate beak. The dorsal margin is convex and crested; the lower
outline is also convex. The claws are toothed more as in C. macru-
rus than the following. The basal spine springs from the claw
itself and not from the post-abdomen as in the next. Length 0.\}
mm. to 1.0 mm.

Sp. 5. Camptocercus liUjeborgii, Schoedler.

(Plate I. Figs. 7—8.)

Head depressed, rounded in front: beak divided at the end by the
extension of the fornices. The terminal claws are pectinate for
their entire length, and the basal spine is seated on the end of the
post-abdomen. This species, in the main, closely resembles C.
macrurus.

Sp. 6. Camptocercus rotundus, Hemck.

The second of the two species found in America is this short,
strongly carinated form, which is known from a single gathering.
It differs from all the above species, with, which it agrees pretty
well in shape, by its more compact form; high dorsal keel (which
extends the entire length of the body); the long antennules, which
extend far below the beak; and the somewhat pointed beak. The

STATE GEOLOGIST. 85

head is much as in the last, but it is not certain that the beak is
cleft, although it has a peculiar form (not indicated in the figure)
near the end. The length is 0,7 ram. The terminal setse of the
antennules are very unequal; but in most points, as in the armature
of the post-abdomen, the details resemble C. macrurus.

III. — Genus Alonopsis, Sars.

This curious genus includes three species of small lynceids,
which exhibit a combination of characters The form of the beak
and head is like that of Pleuroxus, which the form and sculpture of
the shell otherwise resembles. The back is extended more or less
in a knife-like ridge above, thus resembling Acroperus, a resemblance
hightened by the excavated lower margin. The form of the post-
abdomen approaches that of Acroperus, but in that genus it is of
about equal width throughout and in this it rapidly narrows. The
internal organs and feet are of the typical lynceid form, while the
antennae are as in Pleuroxus.

The type of the genus, A. elongata, is apparently much closer to
Acroperus than the two species which have been identified in
America.

Shell sub-rectangular, high, produced into a ridge above; lower
margin convex anteriorly, concave behind; beak rather long; an-
tennules slender; antennae with eight seta3; abdomen long, nar-
rowed toward end, incised at the extremity; claw rather large, with
median spines and a basal thorn; third foot with a long bristle.
Male smaller, without the carina above; orifice of sexual organs in
front of the claw, which is removed from the anterior margin. The
young are more elongate and (sometimes) have hexagonal reticula-
tions instead of the usual strong diagonal strife. Motion slow.

Sp. 1. Alonopsis elongata, Sars.

Lynceus macrurtis, LIHVIN.

Lynceus mnxirurus, ZENKER, LEYDIG.

Alorui elongcUa, SARS.

Acroperus inierviediiis, SCHOEDLEB.

Alonopsis elongata, P. E. MUELLER.

The shell is wide, the upper margin forming an even curves
manifestly angled behind; ventral margin nearly straight, ciliated
throughout, with a single tooth behind. Fornices large; head nar-
row, not carinate. Post-abdomen compressed, truncate at the end,
armed with a series of marginal spines and of lateral scales; caudal
claws large, with a single spine at the base and two median spines
followed by a series of minute seta3.

86 TWELFTH ANNUAL REPORT.

This form I have never seen, and it seems somewhat doubtful that
the following really belong with it.

Sp. 3, Aloiiopsis latissinia, Kurz.
(Plate E, Fig. 8. Plate G, Figs, 1 and 9.)

Body ver> high, compressed, with a high dorsal keel or ridge;
the upper outline strongly and evenly arched, terminating be-
hind in no angle; lower margin almost angled at the anterior thirds
rounded behind, fringed with long bristles anteriorly, with short
ones posteriorly. Head very narrow; beak extremely long; fornices
small; antennules nearly as long as the beak, straight and narrow;
pigment fleck smaller than the eye. The abdomen is long, some-
what narrowed toward the end, where it is deeply cleft^ the terminal
claw is furnished with a large and small basal spine, while there is
an increasing series of spines extending to the middle.

The elongated spine of the third foot is pectinate and reaches
nearly to the posterior margin of the shell. The shell is marked
by few strong striae which are diagonal except anteriorly where are
a few parallel to the front margin. The male is small and lacks
the crest on the back, while the lower margin is straight; the an-
tennae are longer than the beak and differ somewhat from those of
the female. The first foot has a claw. The post-abdomen lacks-
the anal teeth. Kurz gives the size as 0.5 mm.

The A.merican form varies between 0.45 mm. and 0.55 mm., and
seems to have a higher dorsal keel and longer beak. Kurz speaks
of but a single accessory spine on the terminal claws; there is, how-
ever, a second very minute spine or cluster of hairs in this as well
as the following.

Found in the same gathering with the following near Minnea-
polis (marshy off-set from Bassett's creeknear Oak Lake Addition).*

*NOTE TO ALONOPSis LATissiMA. (See Fig. 1, Plate G.) Since writing the above tlie
males of our American form have been found ; they are shaped as the females, with a
high dorsal keel ; the post-abdomen is rounded, with transverse series of small bristles ;
the claw has a minute median spine, and the iwrus genitalis is anterior and elevated.

Sp. 3. Alonopsis media, Birge.
(Plate E. Fig. 9,)

I give Birge's description verbatim:

"Rostrum prolonged, and shell sharp, somewhat quadrangular in
shape, marked by striae. The dorsal margin is convex, the hinder
margin nearly straight. Its lower angle is rounded and without
teeth. The lower margin is concave and has long plumose setae^

STATE GEOLOGIST. 87

The front margin is strongly convex. The post-abdomen is long
and slender, resembling that of Camptocercus, and is notched at
the distal extremity; it has two rows of fine teeth and some fine
scales above them. The terminal claws are long, slender, with a
basal spine, a spine in the middle, and are serrated. The antennules
are long and slender, but do not reach to the end of the rostrum.
They have each a flagellum and sense hairs. The antennae are
small and have eight (su) setae and two (i^) spines. The labruni
resembles that of A. leucocephalus, but is slightly prolonged at the
apex. The intestine, caecum and color resemble those of Acrope-
rus. There is a trace of a keel present on the back."

The specimens seen in Minnesota resemble this species very
nearly, apparently, but there are some differences. The terminal
claw of the post-abdomen has an increasing series of spines to the
middle; there seems to be no lateral row of scales beside the anal
teeth; the abdomen is rather broad at the base and narrows toward
the end. The shell is not square behind. The lower margin has a
few long hairs anteriorly which are followed by a series of teeth,
and in the concave part a somewhat longer set to a point just be-
fore the lower curved angle.

The pigment fleck is nearly or quite as large as the eye. The
antennule is shorter than the beak (which is almostasin Pleuroxus
hastatus), and has a flagellum about midway; at its base it is nar-
rowed and inserted on a prominence.

The embryo still in the brood sac had a more elongate form and
hexagonal reticulations upon the shell, while the antennules were
longer than the very long beak, and the pigment fleck was smaller
than the eye. Length of female 0.52 mm. The color is darker,
and the stria more numerous, than in A. latissima.

Series B.

This section includes forms with (usually) no keel above, or, if
keeled, the post-abdomen is not long. The majority are highly
arched dorsally, and have comparatively short post-abdomen and
pointed beak. The antennae are usually feeble and the motion slow.

A. Post-abdomen nearly ronud in outline, armed with very long stout spines, terminal
claw with one minute basal spine or none ; greatest hight of shell about equal to
the posterior maiKin.

1. Genus Leydigia.

B. Greatest higbt of shell moderately exceeding that of posterior margin ; post-abdo-
men more or less triangular, armed with bristles ; shell marked with hexagonal
meshes.

(a) Head nearly horizontal, blunt ; post-abdomen prominent in the anal region.

2. Genus Graptoleberis.

88 TWELFTH ANNUAL KEPORT.

(b) Head depressed, acute ; post-abdomen excised near the anus.

3. Genus Crepidocercus.

O. Post-abdomen more or less quadrangular, armed with one or two rows of small
teeth on either side behind ; terminal claws with one or two basal spines ; hight of
posterior shell margin usually less than the greatest hight of shell.

4. Genus l/ynceus.

D. Greatest hight of shell little less than that of posterior shell margin ; post-abdo-
men terete ; terminal claws very minute.

5. Genus Phrixura.

E. Greatest hight of shell more than double that of posterior margin.

(a) Eye and first foot normal.

6. Genus Chydorus.

(b) First foot with a claw which extends beyond the shell.

7. Genus Anchistropus.

(c) Eye absent, only pigment fleck used for vision.

8. Genus Monospilus.

IV. — Gentts Leydigia, Kurz.

In this geuus, both the known species of which are found in
America, the posterior part of the shell and body is emphasized at
the expense of the anterior. The curved posterior margin is equal
to the greatest hight of the shell. The head and anterior part of
the body are of the form characteristic of Alona; indeed, the whole
body is in plan like Alona, but in the back part the organs are all
enlarged. The general form of the body and abdomen recalls
Ilyocryptus; the post-abdomen, in particular is very like that genus.
The last two pairs of feet are much enlarged. The shell is usually
irregularly marked with longitudinal striae; the lower margin
is covered with long spine-like setae. The post-abdomen is armed
with several sets of long spines and aggregations of bristles and
small spines; it is almost round and enormously enlarged. The
intestine is coiled and expanded at the end, but the anal cgecum is
rudimentary. The antennae are heavily spined and have eight sette;
the labrum is more or less hairy. The male has a strong hook on
the first foot, and between the terminal claws of the abdomen is a
peculiar intromittent organ.

Sp. 1 . Leydigia quadrangularis, Leydig.

(Plate H. Fig. 4.)

Lyiweu» quadrangxdaris, leydig, fkic.
Alona Uydigii, schoedleb, p. e. muellee.
Lcydigia quadrangularis, kurz.

The shell is comparable to that of Alona quadrangularis, but
higher behind; the markings are not very distinct; shell trans-
parent. The head is very small; the eye smaller than or of about
the size of the pigment fleck. The post-abdomen is very broad, the

STATE GEOLOGIST. 89

posterior margin nearly the segment of a circle, armed with numer-
ous very long unequal spines which extend only about half the
hight, being replaced by short close hairs; the anal opening is very
high; the terminal claws are long, straightish, and have a small
thorn near the base.

The males are smaller than the femiles, and the abdomen is less
broad; the antennules are longer than the beak and furnished with
a flagellum. The sexual period occurs in September or irregularly.
This species has only been encountered once, during September, in
Poplar river, Cullman county, Alabama.

Sp. 2. Leydigia acanthocercoides, Fischer.

Lynceus acanthoeercoid&s. fischkr, leydig.
Eurycercus acanthocercoides, schoedlek.
Alona acanthocercoides, p. e, mueller.
Leydigia acanthocercoides, kurz.
Leydigia quadrajigularis, herkick.

This species, reported in a previous paper, is, as was said, nearest
like L. acanthocercoides; and I am now able to verify the very in-
conspicuous differences upon which the two are separated. Our
specimens of the L. quadrangularis have the pigment fleck fully as
large as the eye, Kurz to the contrary notwithstanding, and the
claw of the post-abdomen is present, while in the present species
the pigment fleck is much larger and furnished with lenses; the
spine of the claw is wanting; the labrum is densely hairy; the abdo-
men is narrower, and the shell higher. The shell is very obviously
striped in the posterior portion. The anus is higher than in the
previous species. In other respects the two seem alike.

V. — Genus Gtraptgleberis, Sars.

A genus containing two closely allied species, having some affinities
with Alonella. The shell is entirely reticulated, and there is a sort
of crest along the back; while, on the other hand, the head is flat-
tened and rounded in front. There can hardly be said to be a beak.
Seen from above, the animal resembles some species of Alonella,
but the head is larger proportionally and more horizontal. The
lower posterior angle is spined. The antennae have seven seta3 and
are very long, in this respect resembling Camptocercus. The dorsal
contour is not greatly arched. The post-abdomen has short claws
and anal bristles, but no teeth.

90 , TWELFTH ANKDAL REPORT.

Sp. 1. Graptoleberis testudinai ia, Fischer.

Lynceus testudinarius, leydig, lilljebobg.
Liniceus reticulatus, frig.
Alona testudinaria, schoedleb.
Graptoleberis testudinaria, kuhz.
Graptoleberis mej-mis, BiRGE.

Form trapezoidal; lower margin straight, armed behind with two
teeth, thickly beset with long hairs in front; the dorsal margin is
not greatly elevated, rounded at the posterior angle, forming a
slight "hump" where it unites with the head shield. The head and
shell are reticulated with hexagonal or quadrangular markings.
The shell gapes below and rises to a sharp ridge above. The an-
tennae have long rami, the antennules being hardly longer than
the fornices. The eye is large; the pigment fleck is small. The
post-abdomen is narrowed toward the end, rounded in front; the
terminal claws are small and have two basal teeth. The dorsal
margin of the post-abdomen is covered with tufts of hairs. The
winter eggs have no ephippium. Length 0.55 mm. to 0.7 mm. The
male is smaller and has a lower dorsal keel; the post-abdomen is
excavated behind.

The only differences between the Minnesota specimens and the
typical European form seemed to be the absence of the very minute
spines on the front of the terminal claws. The eye and pigment
fleck are of about the proportions figured by Kurz. Birge's figure
of the post-abdomen does not agree with his description fully. Our
Minnesota specimens have an obvious but not high keel.

Sp. 2. Graptoleberis reticulata, Baircl.

Alona reticulata, baird, p. e, mdeixer.
Lynceus reticulatus, lilljeborg, leydig.
Alona csocirostris, schoedler.
Graptoleberis reticulata, sars, kukz.

Shell almost rectangular, reticulate, ventral margin straight,
ciliate anteriorly, with two teeth behind. Pigment fleck smaller
than the eye. Post-abdomen short, narrowed towards the end,
dorsally covered with clusters of spines; caudal claws with a minute
tooth at the base. Length 0.4 mm. to 0.5 mm.

The pigment fleck is nearer the end of the beak than the eye, and
is smaller than in the previous species, but, on the whole, there is
perhaps, too great similarity.

STATE GEOLOGIST. 91

VI. — Genus Crepidocercus, Birge.

The characters of this group place it rather near Alonella or be-
tween that and Pleuroxus. Form sub-quadrate with rounded
angles; dorsal line uniformly arched, terminating in a sharp angle
behind; lower margin convex, armed behind with a single spine as
in Pleuroxus unidens, and along the entire length with loose setae.
Beak of moderate length, acute. Post-abdomen deeply incised in
the anal region; lower posterior margin straight, rounded at the
apex; ventral margin straight or concave; claws with a single basal
spine and a few teeth. The post-abdomen is shoe-shaped and
armed with transverse rows of sette.

The antennae are large, having eight setae and the usual spines.
Shell smooth or reticulate.

Sp. 1 . Crepidocercus setiger, Birge.

(Plate F. Fig. 13.)

Length 0.4 mm. to 0.5 mm. Minnesota specimens measured 0 5
mm. This, the only species of the genus, is but rarely encounter-
ed, and is so peculiar as to be easily recognized when seen. Alona
intermedia has a post-abdomen with clusters of bristles, but in
Crepidocercus the post-abdomen is more as in species of Graptoleberis
than any other genus. The markings upon the shell are very
indistinct.

Yii. — Genus Lynceus, 0. F. Mueller.

The perplexing inter-relations between the three genera Alona»
Alonella and Pleuroxus give rise to the utmost confusion. No two
authors are agreed as to their respective limits, and the points given
by Kurz, who has carefully gone over the ground, are obviously
insufficient. Although there may be practical benefits to be derived
from the continuance of the nomenclature in use for groups which
in the general view can be distinguished, the value from a theoreti-
cal standpoint is reduced to a minimum.

The genus Camptocercus (including here Acroperus, which differs
solely in the form of the abdomen, as a sub-genus) passes through
Alonopsis into the group represented by Alona. Leydigia, although
very near such forms as Alona quadrangulata, may be conveniently
distinguished as a transition to species like Ilyocryptus.

92 TWELFTH ANNUAL REPORT.

Phrixura, Qraptoleberis and Crepidocercus, each containing few-
species v/hich can be readily recognized, fill a place in the system;
but it is practically impossible to distinguish Alona from Pleuroxus
without instituting the very indefinite genus Alonella to contain a
variety of small intermediate forms. Percantha, Rhypophilus,
Harporhynchus and Pleuroxus seem to be pretty generally regarded
as constituting a single group which may be recognized by the
long rostrum, high shell and greater development of the antenna
bristles. Alona, on the other hand, with its broader fornices, shorter
beak, fairly developed antennae, and more rectangular shell, is, per-
haps, the pivotal point of the group. According to this view, then,
the old name Lynceiis is revived for the aggregate; and the other
names are retained, in part, as titles of largely conventional groups
or sub-genera, thus:

Genus Ltnceus.

Sub-genus Alona.

Section A. Alona vera.

Section B. Alonella.
Sub-genus Pleuroxus.

Section A. Pleuroxus verms.

Section B. Leptorhynchvs. '■

Characters of Percantha and Rhypophilus are combined in the
species P. procurvus, Birge, so that one must be dropped or new
diagnoses formulated. I am not sure that the same species is not
at first Pleuroxus verus 2 and only later assumes the form known
as Rhypophilus. So with Percantha the amount of serrature of
the posterior margin is in part a question of age.

Sub -genus Alona.

This group contains two sections which resemble each other in
form and, in general, in detail; but it is exceedingly difficult to
formulate a diagnosis that shall strictly limit it. The form is
generally sub-quadrangular with rounded corners; the terminal
claw is armed with but a single spine at the base; the beak is rather
short; and the prevailing marking consists of longitudinal lines.

Section A. Alona {vera). Baird.

This genus contains a large number of minute animals which
are widely distributed.

1 Instead of Harporhynchus, a name preoccupied in zoology.

2 Embryos of P. procurvus have the part which is to be curved forward attenuated
before leaving the brood-cavity, however.

STATE GEOLOGIST. 93"

The authors who have done the most to elucidate this genus are
Schoedler, P. E. Mueller, and Kurz. Birge has contributed most
largely, thus far, to the knowledge of American species, which are,
for the most part, identical or very close to the European. No
other genus is so difficult among the Lynceidse, for the most minute
differences are relied upon to distinguish species. The species of
this genus are not greatly altered by the production of the winter
eggs. The males are frequently but little smaller than the opposite
sex, and are recognized by the altered form of the post-abdomen
and the presence of a hook on the first foot. The form is more
perfectly rectangular than in the next section; the shell is only
exceptionally reticulated and very rarely tuberculate, occasionally
smooth. The lower angle of the shell is not armed with spines,
but is generally rounded. There is only one basal spine upon the
claw of the post-abdomen, which usually bears a row of scales beside
the anal spines. The antennee have eight set^e. The claw of the
male post-abdomen is removed from the lower angle.

About twenty species are known, all of which that seemed recog-
nizably defined have been included in the following key, which is
believed to be more nearly natural in its arrangement than that of
Kurz, which would separate the European and American represen-
tatives of the A. parvula group. Many more forms remain to re-
ward the labor of American students. Those mentioned from
Minnesota could probably all be found by a few days search in one-
locality.

Key to Section A, Alona.

A. Shell reticulate.

(a> Reticulations horizontal.

1. A. guttata, Sars.

(b) Eeticulations oblique.

2. A. angulata, Birge.

B. Shell lined, smooth or tuberculate.
(a) Over 0.5 mm. in length.

I. Shell densely striate.

3. A. aanguinea, P. E. Mueller.

II. Shell normally, evidently striate.
* Post-abdomen narrowed at the end.

t Armed with elongate teeth below.
i. A. tenuicaiidis, Sars.

n Teeth of post-abdomen nearly equal.
5. ^. Zineato, Fischer. (Shell arched.)

94 TWELFTH ANNUAL REPORT.

6. A. modesta, Herrick. (Shell straight above.)

** Post-abdomen not narrowed.

+ Antenna; with seven sptae.
(?) 7. A . costata, Sars.

tt Antennas with eight setae.

8. A. quadrangularis, Mueller.

III. Shell faintly, irregularly striped; eye of same size as pigment fleck.

9. A. oblonga, P. E. Mueller,
rv. Shell smooth.

10. A. afflnis, Leydig.

{b) Under 0.5 mm. iu length.

I. Post-abdomen armed with a row of hairs terminating in large teeth.

11. A. dentata, P. E. Mueller.

II. (One or) two rows of teeth present.
* Shell densely and evenly striate.

)2. A. elegaus, Kurz.

** Shell not densely lined.

t Shell smooth or lined longitudinally.

t Teeth of post-abdomen unequal, the lower ones enlarged.
13 A. porrecta, Birge.

ti Teeth nearly equal.

§ Form elongated ; abdomen with a lateral line of spiny scales.

14. A. spmifera, Schoedler.

§§ Form squarish ; abdomen with a lateral line of simple spines or bristles, or
neither.

15. A. parvula, Kurz,

16. A. glacialis, Birge.

iti Clusters of bristles, not spines, on the posterior edge of the post-abdomen.

17. A. intermedia, Sars.

tt Shell smooth or tuberculate.
18, 19. A. tuberculata, Kurz, Herrick.

Sp. 1. Aloua guttata, Sars.

A small species of sub-quadrangular form. The beak is very short;
the eye small, but larger than the minute pigment fleck. The shell
is short, with a rounded posterior angle and marked by hexagonal
or rectangular meshes running about parallel with the lower margin.
The post-abdomen is of moderate size, rounded at the apex, with a
series of stout teeth behind; the terminal claw has a minute basal
spine. P. E. Mueller, in Danmark's Cladocera, confused this with
A. intermedia, which he described under this. The post- abdomen
in that species is larger, less rounded behind, and armed with
clusters of spines instead of teeth. The length is about 0.3 mm.
in both.

STATE GEOLOGIST. 95

Sp. 2. Aloiia ang-ulata, Birge.

Dorsal margin considerably arched, terminating in a more or
less obvious angle at the hinder corner; the hinder edge is convex,
as is also the front margin; the ventral margin bears plumose setse.
Beak pointed, extending nearly to level of ventral margin of the
valves. Fornices broad. Shell obviously striated diagonally and
less obviously marked by cross lines. Post-abdom m broad, trun-
cate; about twelve anal teeth, with a series of scales and hairs back
of them." The pigment fleck is much smaller than the eye. Male
smaller; beak shorter; post-abdomen with a lateral row of hairs;
anterior feet hooked; sculpture less distinct. [Birge.J Length of
female 0.4 mm; male 0.35 mm.

Sp. 3. Alona sanguinea, P. E. Mueller.

(Plate I. Fig. 20.)

Body nearly rectangular; ventral margin nearly straight, with
short setae; posterior angle rounded, unarmed. Beak short; pig-
ment fleck much larger than the eye. Post-abdomen large, the
end truncate, broadened; posterior margin rounded, with a series
of spines and a lateral row of scales; terminal claw with a small
spine. The shell is ornamented with fine, close, longitudinal
striations. Length 0.9 mm. Alona elegans is very near to this
and should have followed. In August, 1878, I took an Alona
marked as in A. sanguinea and agreeing with Maeller's description
in all points which can be verified in the drawing. The small size
of the eye is remarkable for so large an animal. I have never again
seen this species; it seems to be very rare here and in Europe.

Sp. 4. Alona tenuicaudis, Sars.

(Plate I. Fig. 11.)

Alona tenuicaudis, sars, p. e muelleb, kubz.
Alona camptocercoides, schoedlek.

Form nearly rectangular; ventral margin rounded, with long
setae, posterior angle rounded. Beak short, pigment fleck smaller
than the eye. Post-abdomen with sides parallel, long, incised
below; lower angle armed with about six strong teeth, remainder
of the series small; a lateral line of scales present; claws with a
strong basal spine. The shell is striate with longitudinal lines.
Length 0.5 mm.

One of the most easily recognized species; not identified in
America.

96 TWELFTH ANNUAL REPORT.

Sp. 5. Alona lineata, Fischer.

Lynccim Uneatus, fischkr, leydig.

Alona lineata. schoedlrr, p. e. muelleb, kukz.

Mona rectangular is, sars.

The upper margin is rouuded, the lower one somewhat sinuate,
with setae of moderate length. The beak is tolerably long, reach-
ing nearly to the level of the lower margin of the shell; the pig-
ment fleck is less than the eye, to which it is much nearer than to
the end of the beak. Post-abdomen short, broad and tapering
toward the end, truncate, armed with about ten large teeth;
caudal claws with a small basal tooth. Shell marked with distinct
lines running horizontally. The ephippial females are recognized
by a deep color and the greater elevation of the back. Length
0.5 mm., 0.6 mm. The male has a weak hook on the first foot, and
the post-abdomen is narrowed toward the end; the terminal claw
has no spine.

The Minnesota representative of this widely distributed species
differs in some respects. The lower margin is nearly straight'and
rather sparsely hairy; the beak is blunt, but, on account of the
spreading of the extremely wide fornices, does not appear so except
under pressure.

The beak reaches nearly to the lower shell margin. The
antennules are narrow, one or more of the setse being elongated^
The dorsal margin is either nearly straight or strongly arched
behind; in either case the greatest hight of the shell is back of the
middle. The pigment fleck is large. The post-abdomen is just as
in A. lineata, but the lateral row seems to be of spines rather than
fringed scales. The shell is marked by rather evident or indistinct
lines. The form agrees pretty well with Schoedler's figure, except
that the posterior shell margin is much higher. The antenna3
have eight setae, but the last one is very weak. The terminal
setae seem sometimes to be spined, as figured byi,Schoedler, but in
some specimens they are perfectly smooth. There is a circlet of
spines on the second joint of the setose ramus. There is a hair on
the inner aspect of the protuberance of the labrum. The eye is
somewhat nearer the pigment fleck than is the end of the beak.
If it is desirable to apply a new name to a form at least so^near the
European A. lineata, it may bear the name£first given it in ray
note-book.

STATE GEOLOGIST. 97

? Sp. (>. Aloua modesta. (Sp. n.)

(Plate H, Fig. 3; and Plate Q, Fi>. 4.)

The length varies between 0.41 mm. and 0.55 mm. The smaller
forms have the back most rounded, while a specimen 0.55 mm.
long will appear very like A. quadrangularis. Males are elongate;
hook of first foot strong, accompanied by a heavy growth of small
spines; terminal claw of abdomen with a minute spine.

? Sp. 7. Aloiia costata, Sais.

Founded practically upon the absence of the eighth seta of the
antenna. The description given by Sars will not render it recog-
nizable so that there is no occasion to repeat it here. In all the
species of this section the eighth seta is small and may be absent.

Sp. 8. Alona quadrangularis, Mueller.

(Plate E. Figs. 1— J.)
Alona sulcata, schoeoleb.

Alona guadrangiilaris, p. e. moeller, eurz, herrick. The further synonomy of
the species may weU be doubtful, for there are species so
closely allied as to render a strict determination difficult.
Lynceui quadrangularis, o. f. mueller, is the name employed, and is thought to be

identical with the Alona quadrangularis of Baird.

Shell quadrangular, highest behind; lower margin straight;
posterior margin curved; lower angle rounded, sti'iped with rather
evident lines which are parallel and straight. The beak is quite
long; the pigment fleck is smaller than the eye. The post-abdomen
is broadest near the end, where it is strongly rounded; the numer-
ous anal spines are strong and emarginated, supported by a lateral
series of scales; the terminal claw and its basal spine (in American
forms) are denticulate (Kurz says smooth in European specimens).
The feet are of the typical Alona form (see plate E, fig. 1). The
shell gland is rather conspicuous; no true ephippium. The abdo-
men of the male lacks the spines, but is otherwise similar. Length
0.6 mm. to 0.7 mm. Less abundant in Minnesota than the next.
Both this and the following species were recognized in 1878, but
were thought to be the same species. (See Microscopic Entomostra-
ca, p. 109.)

Sp. 9. Aloua oblonga, P.E. Mueller.

Alona oblonga, KURZ, BIRGE.
Al07ia quadrangularis, LILLJEBORG.

Differs from A. quadrangularis in the following points: — the
greatest hight of the shell is anterior to the middle; the lines aj^§

98 TWELFTH ANNUAL REPORT.

less evident, and all confined to the lower part of the shell, while
the centre of the valves is marked with very minute strire; the
pigment fleck equals the eye; and the post-abdomen is of about the
same width throughout and hardly as round below. This and the
preceeding species have a well marked keel on the process of the
labrura. The size is greater, this being one of the largest and most
abundant, as well as one of the most striking species. It, perhaps,
should rank as a well marked and permanent variety of the above.
Length 0.9 — 1.0 mm. The abdomen of the male is narrowed at
the end and lacks the teeth. Lakes about Minneapolis.

(A small form of A. quadrangularis in lake Calhoun had the eye
and pigment fleck equal and the terminal claw smooth.)

Sp. 10. Aloua afflnis, Leydig.
(Plate F. Fig. 14.j

I/ynceus affiinis,'LEYI>JG.
Alona affinis, SCHOEDLHR.

Form sub-quadrangular; hight about once and one-half in length;
the dorsal outline forming a regular and low curve from end of head
to upper posterior margin; lower outline very slightly sinuate,
anterior one not at all: posterior angles rounded; head nearly hori-
zontal; eye of moderate size; pigment fleck considerably smaller;
antennules rather large, with unequal sensory hairs at the end, one
spine just above the end in front and a bunch of minute hairs near
the base behind; antennae comparatively large, basal joint spiny,
outer ramus with three seta3, two of which have thorns at their
middle, also a terminal spine; inner branch with two of the termi-
nal setae thorned and the upper lateral seta reduced. The post-
abdomen is very broad and short, expanded below and rounded at
the end; the terminal claws are straiglitish, denticulate, and the
spine at the base is also dentate; there is a series of heavy spines
on the upper margin of the post-abdomen, accompanied by a series
of scales on the side. The shell is unornaraented and fringed below
with short bristles. Length 0.9 mm., or more. This fine species
is recognized by its smooth shell, the horizontal position of the
head, and the form of the post-abdomen; it belongs among the
largest of the genus. Lakes near Minneapolis, not rare.

Birge quotes A. spinifera from Wisconsin. In all probability
that species is the younger stage of the above.

STATE GEOLOGIST. 99

Sp. 11. Alona deutata, P. E. Mueller.

(Plate I. Figs. 12— 13.)

Form sub-rectaugular, somewhat arched above, obscurely longi-
tudinally striated; lower angle obtuse, margined below with short
seta3. Post-abdomen small, slender, armed with a lateral line of
scales and two strong teeth at the lower angle; claw with a minute
basal spine. The form of the post-abdomen is identical with "Har-
porhynchus" falcatus, Sars, which this species also resembles in
having the pigment fleck larger than the eye, and in general form
and the character of the striation. The beak, however, is very
short. In size P. E. Mueller says it is among the smallest of the
genus.

Sp. 12 Alona elegaus, Kurz.

(Plate I. Fig, 14.)

Form rectangular; back slightly elevated, posterior margin high,
lower margin straight. Shell covered with minute striations spring-
ing from the region of the attachment of the head shield. Head
rather large, pigment fleck smaller than the eye. The antennae
have eight setae and a circlet of spines on the second joint of the
inner ramus, and a single thorn on its first joint. The post-abdo-
men is short and broad, rounded at the end, and is armed with
about ten anal teeth and a lateral row of scales. Length OA mm.-
0.5 mm.

Sp. 13. Alona porrecta, Birge.

Sub-rectangular ; ventral line nearly straight; valves marked by
longitudinal striae; beak short. Post-abdomen truncate, with about
twelve teeth, three or four of which at the end are larger, and a
row of hairs above the teeth. Male similar. Length 0.34 mm.
Distinguishable from the following small species in the armature
of the post-abdomen.

Sp. 14. Alona spinifera, Schoedler.

If not the young of A. alfinis, this little species mimics it very
closely. The head is less horizontal and more acute than in that
species, otherwise almost identical excepting in size which is about
one-third. The sensory seta of the antennules are said to be nearer
equal. Found by Birge in Massachusetts and Wisconsin, but not
yet encountered in Minnesota.

100 TWELFTH ANNUAL REPORT.

Sp. 15. Aloua parvula, Kurz.

The body is sub-quadrangular, arched above; ventral margin
straight, rounded behind. Shell marked by longitudinal, feeble
and irregular lines. The post-abdomen is narrower toward the end,
with eight or more teeth; the row of scales is absent; at the end it
is sharply truncate and incised; the claws have short basal spines.
Hardly to be distinguished from the next.

(18 ) Alona parvula, var. tuberculata, Kurz.

4

Alona tuberculata, kurz.
Alona verrucosa, lutz.

The species described by Kurz in 1874, and more at length by
Lutz under a different name in 1878, appears to be simply a tuber-
culate variety of the above. Observations upon the American re-
presentatives of the two forms indicate a close relationship between
them. The shell is covered with rows of tubercles (or depressions?)
which vary in number greatly.

Sp. 16. Alona g-lacialis, Birge.

(Plate G. Figs. 2, 3 and 8.)

I do not know how to distinguish this certainly from A. par-
vula. It, however, seems to have the lower angle of the post-abdo-
men less squarely truncate and the incision less obvious. Birge
says that the abdomen is rounded. I have found specimens which
apparently belong here, with the post-abdomen rather sharply
angled and deeply incised; there were about fourteen teeth with a
row of hairs in front. The form is hardly to be distinguished from
another variety which has a shorter post-abdomen, rounded below,
and with only about seven or eight teeth and with a smooth shell »
This form passes directly into a tuberculate variety, having the
post-abdomen similar but the shell covered with numerous rows of
tubercles. Sometimes a transition from a lined shell to a tuber-
culate shell is seen (as in plate G, fig. 14). Alona tuberculata, Kurzr
is said to have a truncate and incised post-abdomen with no lateral
row of hairs. Birge thinks these identical; if so, our form referred
to A. glacialis is identical with A. parvula. There is also a form
found with the above in which no markings are visible and the
shell is considerably arched; these were, however, nearly all ephip-
pial females or approaching that period.

STATE GEOLOGIST. 101

(10.) Aloiia glacialis (?), var. tuberciilata, (Var. n.)

(Plate G. Figs. 4—7 and 14),

•will, then, be our tuberculated Aloiia with a lateral row of scales
and a series of fine spines along the anus.

Aloua glacialis (?). var. Isevis, (var. n.)

is the smooth form Avitli higher dorsal margin.

The antenna of the two last have spines at the end of the rami
of the antennae, a circlet of spines on the outside of the second joint
of the setose ramus, and a spine on the basal joint of the other
ramus; two of the setas at the end of the setose ramus have spines
at the angles. The males found among the above small forms have
the same characters as var. Isevis and the abdomen is rounded at
the end; the claw is situated in the middle of the lower margin, in
front being the opening of the porus genitalis and behind a cluster
of hairs; the spines are absent, but there is a lateral row of long
bristles. A strong hook is found on the first foot. Length 0.3 ram

Sp. 17 Alona iuteriuedia, Sars.

(Plate I. Fig. 15.)
Alona guttata, p. e. mueller.

Form sub-rectangular, rounded below; beak short; shell marked
by longitudinal lines, Avhich may be broken into indistinct rec-
tangular meshes. Post-abdomen short and wide, rounded at the
end, ornamented by clusters of minute spines behind as well as a
lateral row of scales. About 0.3 mm. long.

Section B. Alonella, Sars.

In this group are included small species with a combination of
•characters, forming the link between Alona and Pleuroxus. An
obvious character is the fact that the shell is usually partly marked
by oblique striee. which run in two directions: first, a set extending
forward and upward from the lower posterior angle of the valves;
second, a set springing from the anterior and lower angle, running
across the others. At the central part where these two series in-
tersect, they each become zigzag; thp result is a series of hexagonal
markings, which may extend to the middle of the lower margin.

The beak is short and the fornices broad; the shell is more or
less rectangular, but somewhat elevated in the middle above-

102 TWELFTH ANNUAL REPORT.

There are usually but seven setae on the antenuee, or the eighth
is a minute hair; on the ramus having the lateral setae one of the
terminal setae is frequently reduced. In many cases the whole
shell is marked by minute stride in addition to the proper markings,
but this is also found in some species of the true Pleuroxus. Kurz
gives, as a character of Alonella, the presence of but a single basal
spine to the claw of the post-abdomen; but P. E. Mueller figures
two spines on the claws of one of his species (A. exigua), and
Schoedler figures eight setse on the antenna of A. excisa. American
specimens of A. excisa and of A. pygmaea both certainly have a
very minute eighth seta. There remains, therefore, positively no
point which can be relied upon to distinguish these little lynceids
from Pleuroxus or Alona. Perhaps, however, these species, as a
group, may be recognized by what has already been said. Three
species are found in Minnesota.

A. Rostrum long, bent backwards.

1. A. rostrata, Koch.

B. tiostrum short.

I. Lower ijosterior angle toothed.

(a) Shell more or less reticulate.

* Reticulated areas minutely striate.

2. A. pulcheUa, Herrick.

3. A. excisa, Fischer.

** Reticulated areas smooth.
t Head depressed.

4. A. exigua, Lilljeborg.
tt Head horizontal.

(?) 5. A. grisea, Fischer.

(b) Shell marked by lines running diagonally upward and backward.

6. A. pijgmcea, Sars.

II. Lower posterior angle smooth, shell longitudinally striate.

7. A. striata, Schoedler.

Sp. 1. Alonella rostrata, Koch.

Lynccus rostratus, koch, lilljebokg, schoedler.
Alonella rostrata, sars, kurz,
Alona rostrata, p. e. mueller.

Body long, rapidly narrowed behind; dorsal line strongly arched
in front toward the depressed head; the lower margin straight, with
0 — 3 small teeth at the angle. The fornices are broad, but the beak
is sharp; the pigment fleck is but little smaller than the eye, to
which it is three times nearer than to the beak. The post-abdo-
men is long, very much as in A. excisa, but longer. Length 0.4 —

STATE GEOLOGIST. 103

0.5 mm. Schoedler says the lower margin is concave and the angle
unarmed, a condition not inconsistent with specific identity, as can
be seen in many other species. The shell seems to be variably
marked, but most conspicuous are the diigonal, curved strise.
Schoedler compares the sculpture to P. exiguus; Kurz, however,
leaves the impression that only slight reticulation is present in the
female.

The male has the post-abdomen narrowed, ornamented with
clusters of hairs behind, and the small claws have no basal spine,
while the genital opening is in front of the claws.

Sp. 2. Alonella pulchella. (Sp. n.)

(Plate Q. Figs. 1—3.)

A minute form very recently' obtained is described under the
above name. Although closely allied to A. exigua, this species is
more like Graptoleberis than any other member of the genus. It
is the smallest of the lynceids, excepting A. pygmasa. The shell
is high and rather strongly arched; the posterior margin is short
and armed with four teeth below, which point in different directions
as in Graptoleberis. The head is short and the antennules long.
The pigment fleck is of moderate size, but. smaller than the eye.
The post-abdomen is short, rounded below, and armed with sharp
and small anal teeth, besides which is an inconspicuous row of
minute setge. The claw is very small, and has a single very minute
tooth. The shell is marked by reticulations, which below are
regular hexagons but above pass into elongated meshes, and finally
on the beak and head become longitudinal striations. The areas
are lined as in A. excisa. Thus this species combines the form of
abdomen of A. exigua with the teeth of Graptoleberis and the
markings of A. excisa.

Length hardly 0.27 mm. Motion active. The specimen figured
contained a single large ovum. The head may possibly have been
somewhat protruded by pressure. Habitat, vicinity of Minneapolis.

Sp. 3. Alonella excisa, Fischer.

(Plate E, Fig. 6; and Plate G, Figs. 10. 11.)

Lynceits e.rcisus, fischek.
Pleurozus excisiis, schoedler.
AloneUa excisa, kurz.
/ Pleuroxu-s insculptus, birge.

This species is closely allied to Alonella exigua; yet that species
shows appreciable differences, (which can hardly be claimed, per-

104 TWELFTH ANNUAL REPORT.

haps, for Pleuroxus insculptus.) The various authors who have
written of this lynceid have all laid emphasis upon the sculpture of
the shell, almost to the exclusion of other points in the description.
Prof. Birge has found a quite different form, apparently, which has
the same peculiar markings; and even the common Alona oblonga
has a part of the valves covered by minute sti'iations. Schoedler's
figure of this species is unrecognizable; but, as identified by Kurz,
the species seems undoubtedly the same that is common in shallow
pools in Minnesota, during autumn, and probably also in Massa-
chusetts.

The variations to which this species is subject are considera-
able and may account for the marked disagreement in the
accounts of our different authors. Schoedler gives his specimens
a length of .20-.25 mm., while Kurz says .35 mm. Birge gives
,27 for the length of Pleuroxus insculptus, and our specimens
varied in the same gathering between .24 mm, and .40 mm.
Schoedler figures three teeth at the lower posterior angle; Kurz
says "several (4);" Birge describes one or two, and Minnesota
specimens show gradual transitions from an inconspicuous angle
to three or perhaps four teeth. These teeth are the extensions of
some of the strong ridges or crenulations which mark the shell.
P. E. Mueller's figures of the shell and abdonaen of P. exigua
would apply to our species perfectly, save the absence of minute
striations; Kurz's statements with reference to the differences bet-
tween these two forms seem to agree only in part with those of
Schoedler. I must here express my suspicion that the Pleuroxus
aculeatus, P. exiguus and P. excisus all belong under this species.
I have seen a small form which lacked the fine striations; and there
appeared to me to be, at times, a slight indication of a second series
of hairs upon the post-abdomen.

The form is oblong, truncate behind, variously arched above, but
usually with a rather low, evenly curved dorsal contour; the lower
shell margin is either nearly straight or convex in front and con-
cave along the posterior third, and is heavily beset with very long
pe3tinate bristles. The head is moderately depressed, with a very
broad, blunt and short beak (in some positions this beak seems
acute, but it is an optical delusion); the fornices are very broad,
covering the antenuules completely; seen from above the head is
broad and truncate in front; the eye is larger than the large pig-
ment fleck, Avhich is nearer it than the end of the beak. The
antenna3 have eight seta3, the last of Avhich is minute; the fivt-

STATE GEOLOGIST. 105

«pined ramus has a strong thorn on the end, and the inner terminal
seta is reduced. The post-abdomen is rather broad and truncate
or somewhat rounded below; its length is very variable, being
short in small individuals; its form is subject to concomitant
variations. The seven to eleven anal spines extend in a series of
miuute bristles above the anus. The lower posterior angle of the
shell bears one to four teeth; the marking consists of wavy ridges
and striae, producing, by the crossing of two sets springing from
the two lower angles, a reticulation covering more of less of the
entire shell. The head-shield and the spaces between these mark-
ings are densely striated. Color yellowish, often opaque. Length
0.24.-0.40 mm. At times abundant. Birge alone has seen the
males; his description agrees with Kurz's account of the male of
A. exigua, save that the former speaks of spines, and the latter of
thorns, along the post-abdomen.

Sp. 4. Aloiiella exigua, Lilljeborg.

iy/tceat? exiguus, lilljeborg, leydig, fric.
Alonella exigua, sars, kurz.
Plciiroxus ex)(jULis, schoedler, p. e. mueller.
? Lynceus acidcatus, fjschee.

Aside from the differences in the male sex as above indicated,
this form is said to have a convex lower margin, a rounded post-
abdomen, and the pigment fleck nearer the end of the beak than
the eye, The absence of the fine striation, finally, is the most
marked characteristic. Length 0.30-0.33 mm. Not identified in
America.

(?) Sp. 5. Alonella grisea, Fischer.

This species is included here on the authority of Kurz. The
shell may or may not be toothed at the lower corner, and is partly
lined and partly reticulate; but the only character which at all
separates this species from the above seems to be the position and
form of the head, which is said to be blunt and nearl}^ horizontal,
as in Camptocercus rectirostris. Is this a transition to Grraptole-
feeris?

Sp. 6. Alonella pyg-msea, Sars.

(Plate H. Fig. 7.)
Alonapygmcea, saks.
Pleuroxus transvcrgus, schoedler.
A-hma transversa, p. e. mueller.
Lyuceus nanui, frtc.
-Alonella pygm(:ca,KViiZ.

106 TWELFTH ANNUAL REPORT.

The form is rotund, much like species of Chydorus in the highly
arched dorsal outline; the beak is rather short and depressed; the
lower outline of the valves is very convex in front, and barely
sinuate behind, where it terminates in a minute spine. The shell
is marked, as in no other lynceid, by lines running diagonally
backward, and only on the lower part reticulated, if at all.

The post-abdomen is short, broad and rounded below; the claw
has a single basal spine. Length 0.20 mm. — 0.28 mm. This is the
smallest member of the Cladocera. In form it so nearly resembles-
Chydorus that upon first sight the writer took it for a member of
that genus. Our one specimen measured 0.25 mm. The shell is-
marked by plications rather than striae, which arch over the back..

Sp. 7. Alonella straiat, Schoedler.

This species is said to resemble A. exigua in habit and sculpture
of shell ; the form is quadrangular and not greatly elevated in the
middle; the lower margin is nearly straight and fringed with
bristles; the posterior angle is rounded and unarmed. The anten-
nules with their setag extend beyond the beak; the pigment fleck is
smaller than the eye and half way to the beak. The post-abdomen
is long and narrowed toward the end; there are seven or eight anal
spines, and two spines on the terminal claw. Length about 0.5 mm.

Sub-genus Pleuroxus.

Section A. Pleuroxus {verus), Baird.

This group of lynceids is most obviously defined by the long
"beak", formed by the extension of the chitinous covering of the
head. (There is rarely a beak in the sense of that word as applied
in the case of Scapholeberis or Daphnia, but the autennules are
simply attached to low orominences on the under side of a broad
shield-like projection of the shell.) This beak-like projection is
acute and often long and either curved backward or even bent for-
ward. The fornices, or lateral projection of the head-shield, are
narrow. The form varies much, but is almost always very strongly
convex above, and the posterior margin is thus only a fraction of
the whole hight of the animal. In some American species the body
is very much elongate, and these also depart from the characteristic
habitus of the genus in having strong longitudinal strise instead of
reticulations. The lower posterior shell angle has teeth which, in
a few cases, extend across the entire posterior margin. The post-

STATE GEOLOGIST. 107

abdomeu is slender, usually truncate and armed behind with a single
set of sharp teeth on either side; the terminal claw has usually two
spines and may be serrate.

The male has a shorter beak, the post-abdomen is more or less
modified, and the first foot has a powerful hook. The winter eggs
frequently have a true ephippium; and sometimes this structure is
like that of Chydorus, toward which the round forms of this genus
seem to lead. There are upwards of a dozen valid species, several of
which are American.

Key id Section A, Pleuroxus verus. •

§ Beak not curved forward.

A. Shell reticulate.

(a) Post-abdomen very narrow.

1. P. hastatus, Sars,

2. P. stramineus, Birge.

(b) Post-abdomen not very slender.

* Terminal claws with two spines.

3. P. trigonellu-', O. F. Mueller. (?)
?. P. ornatus, Schcedler.

** Terminal claws with a single spine.

4. P. acutirostris, Birge.

B. Shell smooth, except upon the front margin.

5. P. adunctus, Jurine.

C. Shell striped,

(a) Shell very long and low.

* With one tooth below.

10. P. unidens, Birge.

** Without a tooth ; female with a hook upon the first foot.

8. P. hamatus, Birge.

*** Without a tooth on the shell or claw on the foot.

9. P. afflinis, Herrick.

(b) Shell high.

* Lower angle spined.

t Autennce with eight setae, anterior margin of valves toothed.

7. P. denticulatus, Birge.
tt Antenupe with seven setae.

6. P. hairdii, Schoedler.

** Whole posterior margin of shell spined (Percantha.)

11. P. truncata, O. F. Mueller.

§§ Beak procurved (Rhypophilus.)

A. Shell reticulate.

* Faintly and regularly.

13. P. glaher, Schoedler.
'** Strongly and irregularly.

108 TWELFTH ANNUAL REPORT.

14. P. personatus, Leydig.
B. Shell striped.

* Posterior margin tootlied.

12. P. procurvus, Birge.
** only lower angle toothed.

15. P. unci7Kitus, Baird.

Sp. 1. Pleuroxiis liastatus, Sais.

(Plate I. Fig. 16.)

PIcuroxus Icevis, saes.
Pleiiroxushastatus, p. e. muelTjER.

* Form somewhat oval, dorsal line strongly curved, posterior mar-
gin short, with a tootb below; head short, baak very long, straight-
ish; shell obscurely reticulate. Post-abdomen very long, narrow,
with small teeth; claw with two basal spines. Color corneous.
The sculpture consists of faint reticulations. The ephippium forms
a truncation of the upper part of the shell. Length 0.50 — 0.55 mm.
The male has a shorter beak; the first foot has a weak hook, and
the spermatozoa are spherical.

? Sp. 2. Pleuroxus stramiiieiis, Birge.

This form is the American representative of the preceediug, if
not identical with it. Birge mentions minute strife in the meshes.
P. stramineus is said to be lower than P. liastatus, while its beak is
shorter. Undoubted specimens of P. denticulatus exhibit the same
differences, an increase in the convexity of the shell accompanying
an increase in the length of beak. The form of the abdomen ap-
pears nearly identical, if we compare P. E. Mueller's plate IV, fig.
18, with the outline given by Birge at plate 11, fig. 11. The color
in both is deep, especially during the period when the winter egg is
forming. The direction of the reticulations is said to differ, but
P. E. Mueller's figure does not furnish positive evidence of this.
Length C.6 mm.

Sp. 3. Pleuroxus trigoiiellus, 0. F. Mueller.

Lynceus trigonellm, o. f. mueller, lievix, lilljeborg, leydig, fric.
Pleuroxus trigoiiellus, schoedler, p. e. Mueller, kurz.
? Pleuroxus ornatus, schoedler.

Dorsal line strongly arched; the beak rather long, straightish;

pigment fleck smaller than the eye. Shell faintly reticulate, the

markings consisting of transparent ridges. Post-abdomen widest

in the middle, attenuated slightly toward the end, ^vhich is truncate;

•claw large, with one long and one very small basal spine. The anal

STATE GEOLOGIST. 109

margin of the post-abdomen has a series of small spines, and the
lower shell-margin is hair^^ The post-abdomen of the male is
somewhat as in Crepidocercus, and densely hairy; the first foot has
a moderate hook.

To judge from Kurz's statements, P. ornatiis, Schoedler, is not
specifically distinct. Not yet identified in America.

Sp. 4. Pleuroxus aciitirostris, Birge.

' This form, with Harporhynchus, imitates in some respects the
Alonellffi, from which they differ in having the beak elongated and
recurved. Birge's description does not state what the form of the
fornices is, but he intimates that the general resemblances are with
Pleuroxus. The general shape is as in P. hamatus,

''The post-abdomen is broad, compressed, truncated, with numer-
ous tine caudal teeth. The terminal claws have only one basal
spine." "The valves are reticulated as in P. [Alonella] insculptus,
although not so plainly." Length 0.35 mm. Southampton, Mass.

Sp. 5. Pleuroxus adiinctus, Jurine.

Monoculu^ adunctus, jueine.

Pleuroxus adunctus, schoedlee, p. e. moellek, kuez.

Very like P. trigonellus, but with the back more strongly arched^
The anterior part of the shell is striped. The beak is shorter than
in P. trigonellus, but no other permanent differences are discover-
able. The temptation to believe this a mere varietal form of P.
trigonellus is great. Indeed, four species (the two here noted, P.
bairdii and P. denticulatus, Birge,) are very nearly related. The
ephippium, where known, is marked by minute punccation and a
darker color.

Si>. 6. Pleuroxus bairdii, Schoedler.

Pleuroxufs trigonellus, baird.
Pleuroxus bairdii, kurz.

This form, so far as can be gathered from Baird's brief descrip-
tion and figures, differs from the others in having the shell marked
by straight parallel lines running diagonally backward and upward,
and in lacking one of the terminal bristles on the 5-setose ramus of
the antennae. The first is a possible but unusual structure, while
the second might result from an overlooking of the very small seta
which fills this place in the other forms. Baird himself did not
distinguish it from P. trigonellus.

110 TWELFTH ANNUAL REPORT.

Sp. 7. Pleuroxus cleiiticulatus, Birge.
(Plate G. Figs. 12—13.)

Resembling very closely P. aduuctus, which, however, has a
broader post-abdonieu than the ordinary P. denticulatus. The
posterior angle of the shell is armed with from one to four (gener-
ally three) teeth. The beak is very long.

The character most emphasized by Birge is a series of teeth along
the anterior margin of the valves. The same thing is found in P.
procurvus, as I have repeatedly satisfied myself. In certain posi-
tions these teeth do not show, or the smaller teeth on the lower
margin only appear. P. aduuctus, as figured by Schoedler, has
similar teeth on the lower margin, and very likely has them anteri-
orly. The edges of the valves are heavily fringed with pectinate
setfe. The male has a shorter beak and the post-abdomen simplj'
rounded without the peculiar modification seen in P. adunctus.

There seem to be two varieties in Minnesota both of which have
the characteristic irregular striations of the shell, which radiate from
an irregularly marked or unmarked area in the center toward the
edges; both have the toothed posterior angle and the serrated post-
erior ailgle and tlie serrated anterior margin. But the common
form is much longer, with the dorsal margin less convex and the
beak shorter. The robust form lias a larger pigment fleck, while
the post-abdomen is shorter and more robust, resembling more
nearly Schoedler's figures of the abdomen of P. adunctus. There is
another variation or abnormalitj^, in which the lower margin is
quite concave. The resemblance to P. procurvus is remarkable in
some phases.

I have collected this species in Blount springs, Ala., in the St.
Croix river, and at various intermediate points, as well as very often
in Minnesota.

Sp. 8. Pleuroxus liaiiiatus, Birge.

(Plate H. Fig. 1.)

This species is smaller than those of the preceding group and
forms a transition to the two next to be described in the greater
elongation of the shell, which is, however, higher and more strongly
arched. The head and beak are much as in P. denticulatus. The
lower margin is concave posterior to the middle and slightly convex
at the posterior angle, which is unarmed. The lower margin is
hairy. The markings are as in P. denticulatus, but, in addition,

STATE GEOLOGIST. Ill

there is a set of horizontal strias all over the shell. The post-abdo-
men is widest in the middle and almost exactly as in P. denticula-
tus. The first foot bears a claw such as ordinarily distinguishes
the males.

The only specimens which I have seen were from the Tennessee
river, near Waterloo, and near Decatur, in Alabama, My notes
contain no reference to the minute striations, which could perhaps
be hardly seen with the instrument emplo3'ed. The process of the
iabrum is long and rather acute, the beak moderate, and the pig-
ment fleck very large. The markings on the anterior of the valves
are irregular and are inter-connected by cross lines or anastomoses.
Ova two. (The genus Anchistropus has a hook upon the first foot,
•but is like Chydorus.)

Sp. 9. Pleuroxus aflflnis. (Sp. n.)

(Plate H. Fig. 2.)

A small species with elongated shell and longitudinal striae, form-
ing a link between the preceding and the next, to which it is
<jlosely related. Shell broadest in front, upper contour nearly
straight; anterior part of the lower margin evenly arched, posterior
margin rather low. Head very short; beak very long, narrow and
somewhat incurved; antennules and antennas very small; eye evi-
dently larger than the pigment fleck. The post-abdomen is as in
P. denticulatus, or a little Ioniser proportionately. The markings,
«o far as observed, consist of diagonal, faint, numerous and parallel
lines posteriorly, and others springing from the anterior margin.
There is no tooth behind; the teeth on the post-abdomen are small
and not numerous. The upper margin of the shell is not sharp but
rounded. Thus this pretty and unique form is clearly distinguished
from all its allies althongh unfortunately only this very imperfect
description and schematic figure can be given. Found in Weakly
pond, Culbert county, near Florence, Alabama, where with an
Alona, Chydorus sphasricus and Scapholeberis, it formed the clado-
ceran fauna of the pool.

Sp. 10. Pleuroxus unidens, Birge.

(Plate F. Fig. 15).

An extreme among these elongated species, the length of body fall-
ing little short of double the hight. The dorsal line is very flat
and slightly but evenly arched; the lower margin is evenly convex

112 TWELFTH ANNUAL REPORT.

or nearly straight, covered by long pectinate bristles. The head is
short, and the beak is long and sharp; the autennules are of moder-
ate size, with a lateral seta one-fourth from the end; pigment fleck
less than the eye; anteunte rather long, with strong thorns on the
terminal joints. The post-abdomen is long, as in P. hastatus, sides
nearly parallel; anal teeth sharp, small and numerous; claws pec-
tinate, with two strong basal spines. The shell is strongly striate
with longitudinal striee, which are parallel with the different mar-
gins. Birgesays that there is a reticulated area. The lower angle
is rounded, and anterior to it is a small tooth directed backward.
This species is distributed throughout the Mississippi valley. I
have notes of it from Swan lake, near Decatur, Alabama. It is
often rather abundant about Minneapolis, but is thought by Birge
to be absent from the eastern states. Almost all the specimens I
have seen are very dai'k, often brown, so as to appear to the eye
like dark specks as they swim about. The length varies from 0.55-
nim. to 0.85 mm. About 0.60 mm. is a common size, according to
my observation. Birge mentions a rudimentary sixth foot in this
species. This organ is found in Eurycercus and other lynceids,
according to Schoedler.

Sp. 11. Pleiiroxus trimcata, 0. F. Mueller.

Lynceus truncatus, mueller, koch, zaddach, lievin, fischer, lilljeborg. ley-
dig, FRIC.
Pcrcantha trimcata, baird, schoedler, kurz.
Plcuroxus truncatus, p. e. mueller.
Pcrcantha breviroHris, schoedler.

This species is widely distributed in Europe, but is replaced in
America by the following. The shell is high, the dorsal contour
arched; beak rather long and straight; lower margin slightly con-
vex, setose; posterior margin straight, armed with very strong teeth
entirely across it; the anterior margin also is dentate, as in the next.
The valves are covered with strong striae, springing from the an-
terio-central part and radiating toward the free margins. The post-
abdomen is of moderate size and in form much as in the next. The
ephippium causes a considerably change in form and coloration. In
the male the beak is shorter, and the abdomen has finer teeth. The
first foot has an extraordinarily large hook. The length is about
0.5 mm. to 0.6 mm. Pcrcantha brevirostris,Schoedler, differs in the
length of the beak only.

STATE GEOLOGIST. 113

Sp. lli. Plenroxiis prociirviis, Birge.

(Plate E. Figs. 3, 4.)

In size and general appearance this most interesting species is
similar to the above, and, especially, to P. deuticulatus. The gen-
eral form and even the details of structure agree almost to identify
with the latter. The structure of the posterior margin is like Per-
cantha, while the rostrum it bent abruptly upwards as in Rhypo-
philus. In small individuals the length is greater proportionally.
The lower margin is slightly convex or nearly straight, and fringed
by bristles v/hich are stroulgy pectinate; the anterior and lower
margins are toothed as in Percantha. The shell gland is more as
in the Daphnidie than most lynceids. The number of posterior
teeth is variable. The ephippium is as in P. deuticulatus. Length
O.iO mm. to 0.50 mm. Not rare, but less common than P. deuticu-
latus. The male post-abdomen is like that of P. denticulatus; the
rostrum is as in the female.

Of the species following it may suffice to say that they are corpu-
lent, filth-loving representatives of P. trigonellus, P. adunctus and
P. bairdii, respectively, which have turned up their noses at a super-
ficial existence and buried themselves in the mire and debris at the
bottom of the pools. It. might be fanciful to assume that the curved
snout is used for "rooting," but the fact that these "Schmutz-
peterchen^' lynceids would fiud a long straight beak in the way is
suggestive.

Sp. 13, Pleuroxiis (Rijjjophilus) glaber, Schoedler.
Pleuroxus personatus, p. e. mdeller.

The shell is high and squarish, the fornices narrow, the beak
slightly pro-curved, the lower margin nearly straight, with two or
more teeth at the posterior angle. The antenujs have seven sette
only. The male is almost exactly as that of P. trigonellus. Length
0.55 mm. to 0.65 mm.; male 0.5 mm.

Sp. 14. Pleuroxus (Ryjiophilus) peivsouatus, Leyclig.

That this species is really distinct is by no means certain; how-
ever, it is stated that the shell is less regularly aud more markedly
reticulated, aud the markings lack the elevations described under
P. trigonollus, which are present in the previous species. It lives
in filth and covers itself with it.
8

114 TWELFTH ANNUAL REPORT.

Sp. 15. Pleuroxiis (BijpojMlusj uiicinatus, Baird,

The shell is ridged with lines running upward and backward, as
in P. bairdii; the lower angle of the shell has three teeth, and the
beak is more horizontal than in the above. In size and characters
this is almost identical with P. bairdii, with which it occurs in
England.

This completes the list of swine-lik% members of the genus; these
well deserve to be studied from a morphological stand-point.

Pleroxus nasutus^ Gay, is a poorly described form from Chili, re-
sembling, according to Schoedler, P. ornatus = trigonellus.

A species of Percantha (Lynceus armatus. Gay) is found in Chili.

NOTE TO PLEUROXus.— The two spccles p. unideus and P. affitiis are quite diverse
from the type of the genus and approach in some respects to Leptorhynchus. P. affinis,
particularly, has a recurved beak. I am in doubt about P. iiamatus and P. acutirostris,
which is said to be reticulated ; but it seems likely that the species above mentioned
stand in closest relation to Leptorhynchus.

Section B. Leptorhynchus^ Herrick. ^

The species for which Sars formed the genus Harporhynchus is
of Alona-like habit, but has a beak which exceeds that of any known
Pleuroxus in length, being simulated in this respect b}' the Amer-
ican P. acutirostris, which is, however, in other respects more nearly
allied to Pleuroxus.

Leptorliyuclius faicatus, Sars.

Harporhynclnis faicatus, saks.
Alonafalcata, sars, p. e. muelleb.

Body oblong, arched above; ventral margin nearly straight, setose,
with a spine at the posterior angle; beak strongly curved, folded
laterally; pigment spot larger than the eye. The post-abdomen is
wide, sides nearly parallel, armed with a few strong teeth below
and a lateral line of spines; caudal claw with a single small basal
spine.

Yiii. — Genus Phrixura, P. E. Mueller.

Oblong, wide; posterior shell-margin little less than whole hight.
Post-abdomen terete, obtuse at the end, which is armed with a
cluster of spines of which the terminal ones are similar to the others.

1 Harporhynchus is preoccupied in ornithology.

STATE GEOLOGIST. 115

Sp. 1. Plirixiira rectirostris, P.E.Mueller,

(Plate I. Fig. 18.)

Beak acute; shell striated longitudinally, slightly arched above;
ventral margin rounded, with a round and uuspined angle behind.
Length 0.5 mm. Not yet encountered in Minnesota.

IX. — Genus Chydorus, Leach.

This genus, if it be really of generic value, contains minute
rotund animals which appear in the water like animate pin-heads
of small size. I'heir motion is a rolling, wavering hobble; and the}'
live by preference upon vegetation, or in slime at the bottom of
pools. Occasionally they may be seen in sunshiny weather, dis-
porting themselves near the surface in immense numbers. There
are two common species, and six more which are more rare or in
part not valid.

The sexual period occurs at two different periods (i. e., May —
June, and December), but in probability is not confined to au}'
periods. The males, which only rarely are found even in these
periods, have the abdomen narrowed or excavated to accomodate it
to the peculiar alteration of the brood-cavity which takes place in
the sexually mature female. The connection takes place by the
insertion of the abdomen within this chamber, which is facilitated
by the reduced size of the abdomen. The modification of the shell
of the brood-cavity above referred to consists in the thickening of
the wall posteriorly, which may or may not result in the deforming
of the shell, as shown in plate F, fig. 7, taken from Kurz. This
may be termed an ephippium, although it differs somewhat from
the modified shell so called in Daphnia. The male element consists
of nearly round nucleated cells, and the opening of the vas deferens
is anterior to the terminal claws. The members of this genus are
among the most minute forms of the family or the entire group.
Concisely put, the characters are as follows:

Form globose, not obviously truncate behind; head terminating
in a sharp, long, curved beak, which lies close upou the anterior
margins of the valves; antennas short; eye larger than the pigment
fleck; abdomen flattened, excavated in the jnale; intestine with nc
anterior casca, doubly convoluted, with an anal cee^um. Three spe-
cies found in Minnesota.

^16 TWELFTH j\NNUAL KEPORT,

Sp. 1. Chydorus sphiericus, Mueller.

(Plate F. Figs. 4, 7, 8 and 10.)
Lynccus sphcuricus, o. f. mueller, m. edwards, koch, zaddach. lieven, Fischer

rjLLJEBOBG, LETDIG, TOTH, ZENKER, FRIC.

Monoculus splicvriciLs, jurine.

Chydorus muelleri, leach.

Chydorus sphtericus, baird, schoedler, p. e. ivruELLEE. ltjtz, kurz, birge.

Form nearly siDlierical, as seen from above broadly oval; in young
specimens truncate behind; anteuuules of moderate size, in the male
very large, with curved flagellum near the middle of anterior mar-
gin; pigment fleck often nearly as large as eye; beak of moderate
length, blunt in the male; first foot strongly hooked in the male;
post-abdomen short, broad, rounded at the end, armed with S — 9
sharp teeth; shell reticulated with polygonal meshes. Color light,
unspotted. Length 0.50 mm.

This species occurs in Spring earlier than most forms, and is
ranked as the most abundant of the micro- Crustacea, being found
over the whole circumpolar hnd-area. The ephippium for the
winter egg was observed by Kurz, but the period at which it is
formed seems variable.

C. sphaericus of a previous report seems to have been the follow-
ing species which is more common in Minnesota in the clearer
lakes. A small form in our large lakes measures 0.3 mm.; it may
be distinct.

Sp. 2. Cliydorus globosus. Band.

(Plate F. Figs. 1,2, 3 and 9.) •

C?!l/d0/H.S £f?0?)OS)iS, BAIRD, LILLJEBORG, SCHOEDLEK, LEYDIG, P. E. MUELLER, FRIC, 'f^
KURZ, BIRGE. ,^i

I

Form globose, very broad; antenuules very large with a strong f

lateral seta on a small elevation; swimming antennse exceedingly i

small; the shell gland is well developed; the pigment fleck is much ^

smaller than the eye; beak very long and incurved; post-abdomen '

rather long, more slender than the last, broader near the end which j"

is truncate, bearing about 20 spines on the margin near which is a ;'

lateral series of minute bristles; the terminal claws are straightish, i

spined along the basal half, and have an accessory spine; the shell }

is very indistinctly reticulated and spotted; color dark; length 0.7- ^

0.8 mm.; male 0.55 mm. The males have the abdomen very nar- |;
row for the entire length.

This species is considered rare elsewhere, but is not infrequent in
August near Minneapolis.

STATE GEOLOGIST. 117

Sp. 3. (Jliydorus oralis, Kurz.
(Plate F. Fig. 11.)

Form oval, nearly twice as long as high; beak long; aatennules
two-thirds as lona; as the beak, with two elongated sensory filaments
above the others; pigment fleck nearly as large as the eye; antennae
small; shell margins heavily fringed anteriorly; post-abdomen of
moderate size, rounded at the end, with about 8 teeth near the end;
shell smooth. Length 0.4 mm.

This species is rather near C. sphfericus, differing in having the
shell smooth, antenna3 shorter, and beak longer. This species is
not yet known in America.

Sp. 4. Cliydorus c?elatiis, S hoedler.

(Plate F. Fig. 12.)

Chydorus adunelu.s, Schoedlek.

This small species is about 0.4 mm. long, and resembles the young
of C. globosus in form, from which as well as from all known spe-
cies it is distinguished by the markings of the shell, which consist
of series of rounded elevations (or depressions?) arranged parallel
to the lower margins of the shell and head. The description is very
incomplete, and the only other author who appears to have seen
the animal is Kurz, who adds that the sensory filaments of the an-
tennne are unequal in liight, and that the so called elevations are
really depressions. A form with a few depressions about the edge
and characters of this specids was once seen in the vicinity of Min-
neapolis.

Sp. 5. Cliydorus nitidus, Schoedler.

(Plate F. Figs. 5, 6.)

Shell smooth and regularly punctate; the head resembles C, sphae-
ricus, but the pigment fleck is much smaller than the eye, to which
it is much nearer than to the end of the beak; the post-abdomen is
broader near the end, and bears a row of 10 — 12 teeth on either side.

(?) Sp. 6, Chydorus latus, Sars.

Very possibly a variety of C. globosus, from which it differs in
the shorter beak and greater size. Length 0.66 mm.

118 TWELFTH ANNUAL RErORT.

Sp, 7. Chydoriis piger, Sars.

Sub-rotund, prominent above, sinuate behind; lower and poster-
ior margins rounded, lower margin ciliated. Head movably united
to the body; beak long, separated by an indentation from the head
shield. The shell is broad, as seen from above. Shell punctate
anteriorly and marked below by indistinct oblique strife. Anten-
nules with seven sette and two small thorns on the end of each
ramus. Post-abdomen truncate; the terminal claws with a minute
tooth at the base; posterior margin siuuated, rounded below and
there densely armed with minute teeth. Abdominal setas long and
flexible. Pigment fleck of medium size, much nearer to the eye
than to the beak. Length about 0.33 mm.

(?) Chydorus latifrons, Dana. (U. S. Exploring Expedition, Rep. on Crust.,

vol. II, p. 1274.)

Very tumid; in side view rotund, head not separate, very short-
beaked; beak slender and close to the body, acute; in upper view
animal very broad, truncate anteriorly, the front thereby nearly
as broad as the body; behind low, triangular and obtuse. Feejee
islands.

( ?) Chydoiais albicans, Gay,

from Chili, is imperfectly described; but it is interesting to note the
occurrence of this genus there.

X. — Genus Anchistropus, Sars, (?)

Very similar in form to Chydorus; valves gaping below anteri-
orly; antennules small; process of labrum rounded. Post-abdomen
attenuated toward the end, densely covered with fine teeth; terminal
claws denticulate. First foot with a powerful claw, protruding
beyond the shell. Eye very large. Shell indistinctly reticulate.
Sars says of his Anchistropus emarginatus that on cursory inspec-
tion it would be taken for the young of Chydorus globosus. He
found but few specimens, about 0.35 mm. long. The suggestion is
still possible that the young males of some Chyd'^rus are here mis-
taken for a new genus. The males of Chydorus globosus were not
known till 1878, and their early form is still unknown. The young
females have a tolerably strong claw, though it is not much curved.
I have once found a peculiar lynceid measuring 0.46 mm., with

STATE GEOLOGIST, 119

unevenly but distinctly reticulate shell, slender abdonieu, and a
strong claw whicli Avas dentate. There were several young (more
than two), and the shell in these was more regularly reticulate. All
efforts to find a second specimen failed, and the one seen was some-
what mutilated; hence I am unable to determine its real position.

XL— Genus Moxospilus, Sars.

Head separated by a depression from the body; shell high, com-
pressed, posterior margin somewhat less than the greatest hight of
the shell. Post-abdomen broal ornamented with lateral and post-
erior spines; claws large, with a single basal tooth. The compound
eye is absent, its place being taken by the pigmeiit fleck, which is
the functional eye. ^

3Ionospiliis dispar, Sars.

(Plate I. Fi?. 21.)

Lijnceustenutrostris, FiscBKR, Abh, uebereinige neue Daph. und Lynceidse. p. 427,

tab. Ill, flgs. 9—10 (flde Sars).
Monospiliis dispar, saks, Crust. Cladoc. i Omgn. af Cliristiania, p, 165.
Monospilics dispar, JiaELLBR, Danraark's Clad . , p. 196.

Shell roundish; ventral margin setose; posterior angle rounded,
marked above with numerous impressions, Antenuules small; an-
tenna? long, with seven setae. Post-abdomen short and broad, bear-
ing a series of spines along the excavated posterior margin, and
ornamented on the sides with clusters of bristles. The shell in old
individuals is not moulted but remains as in Ilyocryptus, covering
the greater part of the new shell. The figure shows an old indivi-
dual with its successive coverings still clinging to it. Like Ilyo-

1 So much interest attaches to this species that we reproduce the Latin description of
Sars. " Testa in adultibus valvulis composita pluribus, altera alteri imposita, a latere visa
lata, latitudine maxima in parte antica sita; margine superiore antice valde proniineute,
posteriore et inferiore ciliatorotundatis. Caput mobile, perparvum et valde depressum,
supine impressione parva sed distincta, a testa cetera disjunctum, deorsum in rostrum rec-
tum et breve apice obtuso exiens. Animal supra visum sat compressum, latitudine maxima
capite majore ante medium sita. Pars superior testte et capitis impressionibus numerosis
rotundatis notata. Antennae 1-mi paris minutse structura ut in ceteris Lynceidis ; 2-di paris
sat longie, ramo altero setas 4 et aculeum unum apicalem, altero setas 3 et aculeos duos,
quorum alter longus articulo primo ejusdem rami adflxus est, gerunte. Postabdomen breve
et latum, apicem versus truncatum ; margine posteriore supra obtuse angulato, ad angulum
inferiorem rotundatum seriebus duabus acu'eorum inquelateribus setis vel spinulis brevi-
bus numerosis prceditum ; ungues terminales ad basin aculeo longo armati. Intestinum, ut
in ceteris Lynceidis, in thorace laquem fere duplicem format. Macula nigra unica minima
prope basin antennarum 2-di paris ; maculje infra oeulari in ceteris Lynceidis simillima, in
capite conspicitur, quse. quum oculus verus compositus in omnibus ceteris Crustaceis
Cladodoceris distinctus omnino ab-it, organum quamquam rudimentare visus habenda est.
Animal parum pellucidum, colore fulvescente. Longit, parum supra y^ mm "

120 TWELFTH ANNUAL REPORT.

cryptus, this animal passes its life in filth at the bottom of pools,
and rarely emerges to the light of day. What little visual function
there may be is vested in the larval organ.

The specimen from which the drawing was made measured 0.45
mm. The first glance at this rarest of all entomostraca affords proof
of its unique character. The strongly arched shell is so compressed
as to bear little resemblance to Chydorus. The dorsal line passes
with little angle into the high posterior margin. There is a rounded
angle below, armed with two teeth — the shortened representatives
of the fringing spines of the straight lower margin. The head is
depressed and very short, but the narrow beak is produced to below
the margin of the valves. It is rounded so as to resemble, as seen
in front, a duck's bill. The fornices are narrow and flare so that
the eye is left partly exposed upon the side. The antennules are
not long but slender. The labrum has a very large lamella, which
is crenulate in front and acute below, the labrum proper being large.
The systematic position of this genus is a matter of considerable
interest, for it is the only member of the whole order in which the
larval eye is the only one developed, and the first thought would
be that this must be a primitive synthetic type, in other words,
historically the oldest of Cladocera. Closer study does not warrant
the theory. There is much to indicate that, though essentially lyn-
ceid, it stands in close connection with the higher members of the
family and perhaps has more than a superficial resemblance to such
degraded lyncodaphnids as Ilyocryptus. All things considered,
however, our diagram stands with this genus as a degraded offshoot
of the more typical stem of Lynceidaj.

SUB-ORDER II.— GYMNOMERA.

, This group is easily recognized by the almost entire absence of
the shell, which forms so conspicuous a part in the greater number
of the Cladocera. Here it serves simply to form a pouch or brood-
sac for carrying the eggs and embryos. The feet are nearly terete
and prehensile, with but slight indications of branchial appendages.

FAMILY POLYPHEMID^.
Feet five pairs. Antennee with the rami three- or four-jointed.

1. — Genus Polyphemus, De Geer.
Head very large, separated by a depression from the compact

STATE GEOLOGIST. 121

body; shell covering but a part of the dorsal region. Feet all with
an internal dentate, and an external lamellate appendage. Caudal
seta upon a long process of the post-abdomen.

Sp. 1. Polyphemus pediculus, Linn.

(Plate B^ . Fiffs. 4—6.)

Monocuhis pediculiis,L,ii!fSJEUs, \7i6. gjielin', Linn. Syst Nat. FABRicros, Ent. Syst.,

etc. suLZER, Insecten. :manuel, Eucyclop. Metli.
Monoeulns pedicuhis ramosiis, de geer, Mem. pour serv. a I'Hist. des Ins.
Polypliemus oculus, muellek, Zool. Dan. Prod, et Eatomost. cuvier, Tab. element

LATREiLLE, Hist. Nat. Cnist., etc. leach. Edin. Enej'c.
Polyphemmatagnorum, LKXCH, Diet. So, 'Sat. latreille, Cuv. Rig. An. dema-

REST, Cons. Gen. Crust.
Polyphemus pediculus, st:iaus, Mem. Mus. d'Hist.,etc. M. edwards, Hist. Nat. Crust.
Monoculiis polyphemus, JVR\tr&, Hist. Nat. Mouoc.

Cephaloculus stagnorum, lamarck, Hist. An. Vert, bosc, Man. d'Hist. Nat. Crust.
Monoculus ocuhis, g.melin, Linn. Syst. Nat.
Scalieerus pedicuhis, Kocu, Deutsch. Crust.
Polyphemus pedicidus, baird, Brit. Eutom.
Polyphemics oculus, lievin'. Branch, d. Danz.
Polyphemus stagnorum, fischer, Uel)er die in d. Umg. von St. Petersburg, vorkom.

Crust.
Polyphemus pediculus, lill.jeborg, De Crust, ex ord. trib.
Polyphemus oculus, leydig, Naturg. d. Daph.

Polyphemus pediculus, schoedler, Neue Bsitr. zur Naturg. d. Cladoceren.
Polyjihcmus Iwcliii, " " " "

Polyphemus oculus, " " " "

Polyphemus pediculus, p. e. mukller, Danmark's Cladocera. korz, Dodekas n euer
Cladoceren. weismann, Beitr. zur Naturg. der Daplinoiden.
birge, Notes on Cladocera.
Polyphemus occidentalis,'^ herrick.

There are two well-marked varieties of this species: one is found
commonly in the clear lakes; the other, which I have only once
seen, was found in a very shallow weedy marsh. The difference in
size is quite remarkable. Our ordinary form measures less than 1
mm. The larger form, including the stylets, is 1.6 mm. The
ordinary variety, although highly colored, is yet transparent, whil^
the large variety is deep red and quite opaque. The relationship
between the two forms is quite like that maintaining between
Diaptomus stagnalis and D. sanguineus. Some slight structural
differences are observable between the two varieties, as in the form
of the antennules, yet quite insignificant when compared w-ith the
striking difference in size and coloration. Number two may be
called

1 Foiypliemus occidentalis,Dekay = Liiuulus.

122 TWELFTH ANNUAL KEPORT.

Si>, 2. Polyphemus stagiialis. (Sp. n.)

In order to make the relation clear between these forms, I add
measurements of this species, followin^^ each with the correspond-
ing measurement of P. pediculus in parenthesis; animals of the
same age, as far as possible, being chosen. Head (capsule of eye)
0.3 mm. (0.2 mm.); head and thorax 0.7 mm. (0.45 mm.); abdomen
O.T mm. (0.56 mm.): caudal stylet 0.36 mm. (0 26 mm.); caudal
filaments 0.36 mm. (0.3 mm.). Whole length of antennae O.oi mm.
(0.42 mm.); first, second and third joints of the 3-jointed ramus 0.08,
0.06 and 0.10 mm., respectively. The formation of the resting eggs
or "dauer-ei" seems to go on at the same time with the partheno-
geuetic reproduction.

II. — Genus Bythotrephes, Leydig.

Much like Polyphemus, but the external appendage of the feet is
rudimentary, and the abdomen extends out into a most enormous
spine. The single species is that described by Leydig as B. longi-
manus, which was found in the stomach of Coregonus wartmanni.
B. cederstromii, of Schoedler and P. E. Mueller, the latter author
now identifies with the above, and concludes that the supposed
differences arose from "I'etat de maceration des examplaires exa-
mines." (Les Cladoceres des Grands Lacs de la Suisse, p. 11.)
This species may be looked for in the depths of the Great Likes.
(See plate U, fig. 10.)

III. — Genus Podon.
IV. — Genus Evadne.

These are compact oval forms confined to the sea. See Claus,
Zur Kenntniss des Baues der Pohjphemiden, Vienna, 1877, for the
best account of the anatomy.

FAMILY LEPTODORIDyE.

Feet six pairs. Antennae with both rami four-jointed. Body
elongated, not curved, shell very much reduced.

STATE GEOLOGIST. 123

Leptodora liyalina, Lilljeborg,
(Plate N. Figs. 6, 7),

the only species, is found rarely in the larger lakes of Europe and
America.

See Bail, mid Lehenserscheimmg von Leptodora hijallna, Weis-
mann, 1874:; also, Oi)i en dimorph Udvikling samt Generationsvexel
Jios Leptodora, G. 0. Sars, 1873; also, Bklrag til Cladocerenes For-
plantningshistorie, P. E. Mueller.

The work of Sars is particularly valuable, showing that the young
produced from the winter eggs pass through a metamorphosis not
experienced by the summer or partheuogenetic brood. P. E. Muel-
ler mentions the pathological condition induced by the plants of
the Saprolegnia.

124 ■ TWELFTH ANNUAL REPORT.

CHAPTER III.

ORDER COPEPODA.

This extensive order contains minute and predominatingly pre-
daceous animals which constitute no inconsiderable part of the
fauna of fresh and salt waters. They serve a beneficent purpose
both as scavengers and as providing food-supply for thefry of fishes
and other aquatic animals.

Copepods are never enclosed in a bivalved shell but ordinarily
exhibit a more or less elongated cylindrical form composed of two
obvious sub-divisions. There are a few species which, by the great
prolongation and expansion of some of the tergites or dorsal shields,
seem to simulate shelled Crustacea. The anterior part of the body,
or cephalothorax, is composed of ten somites which are frequently
considerably united or fused. Five of these segments constitute
the head and bear respectively the following appendages: first, a
pair of several- to mauj^-jointed antenna3 which are never prim-
arily sensory in function, although they usually are provided with
sense hairs or other like organs; second, a pair of two-branched an-
tennules, which sometimes become almost simple or prehensile;
third, a pair of mandibles in the form of masticatory or piercing
organs, these being usually provided with a palpus; fourth, a pair
of maxillge of various form and function; fifth, a pair of maxillipeds
which not infrequently subdivide in later life to form what appear
to be two distinct pairs.

The five thoracic segments have each a pair of sv\imming feet
consisting typically of a two-jointed base and two like, three-jointed
rami. The symmetry is frequently broken by the retardation of the
development of the inner ramus, while the fifth pair of feet may
become rudimentary and in various ways subserve the organs of
sex. The five abdominal segments are nearly devoid of appendages
and are continued posteriorly by two caudal stylets which bear
strong setse constituting, in many forms, a tail-fin or spring.

STATE GEOLOGIST. 125

All copepods, even such as are, in later life, parasitic, begin their
existence as free-swimiug nauplii, such as are represented on plate
S, fig. 13, and plate K, fig. 8.

Though the vast majority of genera and species are marine, it
would seem that fresh-water copepods make up in the number of
individuals what they lack in variety.

As we are dealing primarily with the fresh-water species, no
lengthy description of the group is here necessary.

The earlier history of our knowledge of the animals of this order
is given by Baird. According to this authority, the first to mention
any fresh-water species of this group was Stephan Blankaart ^ in his
Schou-hurg der Hiqjsen, Wormen, Ma'den, en diegejide Diekens tot
Auisterdam. Leeuwenhoek adds numerous interesting details and
is accredited by Hoek with being to first to discover the relation
between the remarkably diverse stages which occur in the history
of the Cyclops. However, it is evident that he had a very incomplete
knowledge of the nietamophoses.

De Geer gives rather characteristic figures of acyclops in Memoi-
res pour servir a VHistoire des Insectes, vol. vii, 1778,

Mueller, in his great work on Entoniostraca, adds new facts,
defines species and forms the genus Cyclops.

Ramdohr in 1805 gave sundry additions to the knowledge of
these animals in his Beitraege zur Naturgeschichte einiger Deutschen
Monoculus-arten. In this work the post-embryonic history is quite
fully outlined.

Jurine, in his classic Avork Histoire des Monocles qui se trouvent
aux Environs de Geneve, 1820, crystallized what previous authors
as well as his own original experiments had brought to light of the
anatomy and biology of these animals.

Ferussac (Memoire sur deux novelles espices d'Entomostraces)
redescribes known species.

Gunner, Stroem, and Viviana, seem to have had little effect on
the knowledge of the group, though they wrote prior to Juriue.

A recent author attempts to revive the names of Jurine, though
hitherto it has been thought hazardous to attempt a specific identifi-
cation.

The German author, C. L. Koch, who only incidentally studied
this group, distinguished more or less perfectly, a variety of species
which have been reinstated in oui* literature by Rehberg. Although

I Lutinized Stephanus Blanchwdus. Hoek recognized Cyclops brevicaudatus orC.
bicuspidatus as the one described, chiefly through knowledge of the present inhabitants of
the locality .

126 TWELFTH ANNUAL REPORT.

this proceeding seems quite unjust to the careful authors whose
descriptions are recognizable in themselves, thelawof priority must
probably prevail. Koch's Deutschlands Krustaceen appeared in 1838.

Baird's British Entomostraca^ without greatly extending our
knowledge of this order, put in readable form and made available to
English readers what was known, and added interesting facts. He
distinguished two families of Copepoda, (1.) Cyclopidee, (2.) Diap-
tomida3. The first included the genera ( 1 .) Cyclops, (2.) Canthocamp-
tus, (3.) Arpacticus, (4.) Alteutha; and the second the general (1.)
Diaptomus, (2.) Temora, (3.) Anomlocera.

Fischer, who contributed not a little to our knowledge of the
distribution of fresh-water Cladocera, was the next to describe valid
species. He described the species found near Moscow and St. Peters-
burg, Russia.

Oucliakoff is likewise a Russian author, but his writings are quite
unknown to me.

The justly famous Swedish naturalist, W. Lilljeborg, who has
left his mark on so many branches of natural science, has not
neglected the microscopic Crustacea of his fatherland. Om de inom
Skaane foerekommande Crustaceer af ordningarne Cladocera, Ostra-
coda och Copepoda is the somewhat formidable title of his work,
published in 1855. He recognized the following genera of Cope-
poda: Diaptomus, Temora, Dias, Ichtyophorba, Tisbe, Tachidius,
Harpacticus, Canthocamptus, aad Cyclops, A species each of Diap-
tomus and Canthocamptus is described, and two species of Cyclops.
(It Avould seem from authors' quotations that other species are de-
scribed in an appendix, but the copy I have seen lacks this.) The
author who has done most for micro-carcinology in general is Carl
Claus, of Vienna. His principal works are:

1. "Das Genus Cyclops," etc. In Wiegmann' s ArcMv fuer Natur-
geschichte. 1 857.

2. " Weitere Mittheilungen ueber die einheimischen Cyclopiden."
The same, 1857.

3. Die Freilehenden Copepoden, 1863.

The later work especially is indispensable to the student of Co-
pepoda, though in reality it is more important in respect to marine
Copepoda.

In the meantime a work appeared in Nor^^egiau, with Latin de-
scriptions, from the pen of G. 0, Sars. This has been largely over-
looked. It is, unfortunately, unaccompanied by plates, but the de-
scriptions bear the stamp of the naturalist.

STATE GEOLOGIST. 127

A little later a second brief contribution from this author was
published, but I have not seen it.

Sir John Lubbock in 1863 describes species of fresh-water cope-
pods, but the publication seems no longer necessary.

Heller^ in Tyrol, Fn'c^ in Bohemia, and Uljanin, in Asia, have
studied the copepod fauna.

A Russian paper by Poggenpol and Uljanin is quoted as "A
Catalogue of the Copepoda, Cladocera and Ostracoda of the vicinity
of Moscow," by Rehberg, and as from the ProtokoUe der kais.-na-
turw. antliropol. unci ethnogr. Ges. in Moskau, but by Cragin who
publishes a translation apparently of the same paper, in part, as
from the " Bulletin of the Friends of Natural History."

Hoek, in the Tijchchrift der Nederlandsche Dierkundige Vereeni-
ging (Magazine of the Zoological Society of the Netherlands) 1875,
and later in German in the Niederlaendisches Archivfuer Zoologie,
gave excellent figures and descriptions of some species which Claus
had too hastily treated.

In 1878 A. Gruber gave descriptions of "Two fresh-water Cala-
nida3."

In the same year the first volume of Bradi/'s fine ^''British Cope-
oda'''' appeared. A purely technical work and briefly written, it is
yet very comprehensive and in the main reliable. This is a worthy
successor of the Ray Society's earliest publication on entomostraca
— Baird's great work.

In the sixth vol. of the Abhandlungen d. naturwissenschaftlichen
Vereine zu Bremen, Herman Rehberg gives a systematic review of
synonomy, and in the revision unites several species in a manner
that the present vmter had independently been driven to do. It is
probably impossible either to substantiate or positively deny some
of this writer's identifications of the species of the older authors.

This paper also contains an observation of a hermaphroditic Cy-
clops, which it is interesting to compare with similar anomalies,
described by Kurz in Cladocera.

In the vii Band of the same periodical, Rehberg adds to and
modifies some of the views expressed above. In the same number
is a description of a new species of Temora by Poppe. (The same
species occurs in the semi-saline waters of the Gulf of Mexico, and
had well-nigh gone into print under a new name when this was
seen.)

In the above review we have noticed onl}'' the more important
foreign works on the Copepoda. and those including fresh-water
forms. Dana's magnificent Crustacea of the Wilkes' Exploring

128 TWELFTH ANNUAL REPORT.

Expedition is^ot included because it is essentially restricted to the
marine species, the lew descriptions of fresh-water species, being
quite valueless. Among important contributors to the exclusively
marine Copepoda, are Boek (Oversigt over Norges Copepoder and Nye
Skegter og Arfer af Saltvands-Copepoder), Brady and Robertson^
Lubbock and Glaus.

The history of the American literature can be quickly traced.

Say described imperfectly an American species of Cyclops in 1818.
Haldeman describes in vol. viii, of the Proc. of Phil a. Academy of
Science, p. 331, Cyclops setosa (which may be C. serrulatus). Pick-
ering very imperfectly described a new genus of copepods from lake
Ontario in Dekay's Zoology of New York. This genus is, most
likely, Episcliura of Forbes and, in strictness, ought to rank it. In
1877 appeared "A List of Illinois Crustacea," by Prof. Forbes., in
which two species of Copepoda were described which may rank as
the first descriptions at all adequately framed of American members
of the order. In the annuccl report of the Minnesota state geologist
for 3878, a brief article by C. L. Herrick outlined, in the light only
of the then English literature, the micro-erustacea of Minnesota.
No attempt was made to treat the Copepoda, but two species of
Diaptomus are indicated which will prove valid. Occasional papers
in the American Naturalist and elsewhere follow till, in July and
August of 1882, Prof. Forbes added two new genera and several
species of Copepods, constituting by far the most considerable addi-
tion to the subject yet produced.

In the report of the state geologist of Minn, for 1881, C. L. Herrick
makes a considerable addition to the knowledge of American Cyclo-
pidaB, enumerating ten species, of which six seemed new. This
writer also describes a new genus and several new species of Cala-
nidse, some of which unfortunately are identical with those described
by Forbes and published about simultaneously.

Several articles in the Naturalist bring the bibliography up to
May, 1883, when F. W, Cragin published in the Trans. Kansas
Academy of Science^ ''A Contribution to the History of the Fresh-
water Copepoda." In this paper ten species of Cyclops are described
or mentioned. The author ignored previous American literature
and thus adds somewhat to synonomy. The plates are lithographic,
and are carefully, if not artistically, prepared. A valuable feature
is the translation of the descriptions of Poggenpol's species from
the Russian.

These papers, together with the outline presented beyond, it is
hoped, will form a basis for future work.

STATE GEOLOGIST. 129

Since writing the above, it is brought to my notice that in April,
1881, V. T. Chambers gave some account of a species of the Hai-
pacticidse referred b}'' him to Tachidius, This species is particularly
interesting on account of its novel habitat. Tachidius (?) fonticola,
Cham., is found in the saline waters of Big Bone Springs, Ky., and
thus is ver}' distant from any marine congeners. It is perhaps
doubtful if the generic reference can be sustained, but the species is
worthy of further stud}'. The Diaptomus described by the same
author is hardly recognizable.

FAMILY CALANID^.

This group is pre-eminently marine and contains diverse and
graceful forms mostly with very elongated bodies and antennge.
Of the six genera here enumerated as more or less habituated to
the use of fresh water, two are found as yet only in America
and one is confined to Europt;,

Heterocope, namely, is verj' near Epischura, both being restrict-
ed to fresh water. Diaptomus and Osphranticum are likewise only
accidentally found in the seas, though their nearest allies are marine.
The genus Limnocalanus is as yet found in America only in the
Great Lakes.

In the distribution of genera we here follow Brady, whose defini-
tion of the family Calanidte, including Calanidaeand Pontellidse of
authors, we quote: " Body elongated; composed of from ten to
twelve [obvious] segments. Abdomen nearly cylindrical, much
narrower than the cephalothorax and prolonged at the posterior
extremity into two more or less cylindrical caudal branches
[stylets]. First segment of thorax often anchyiosed with the head ;
fourth and fifth segments also often coalescent. Head only rarely
divided into two segments. Anterior antennae ver}* long and com-
posed of twenty-four or twenty-five joints; that of the right side in
the male often modified for grasping [geniculate]. Posterior
antennae large, composed of a basal joint, from which spring usually
two branches, the primary' branch consisting of two, the secondary
of several joints. Mandibles strongly toothed at the apex, palp
(usually) two-branched. Maxillae strong, and provided with a
many-lobed palp. Foot-jaws strongly developed: first pair very
broad; the basal joints having on the inner margin wart-like pro-
cesses, from which spring long ciliated bristles; the distal extremity
divided into three short joints which are thickly beset with strong

130 TWELFTH ANNUAL REPORT.

and long, ciliated setas; second pair longer and more slender, basal
portion forming two long oval joints; apical portion usually 4-6-
joiuted. First four pairs of feet 2-branched, the outer branches
always three-jointed. Fifth pair either like the foregoing, or much
modified, unlike on the two sides, and in the male forming clasp-
ing organs. A heart is present. Eyes either median and stalked
or paired (lateral) and sessile; in the latter case being often coales-
cent and composed of several lenses. Sexual organs in the female
symmetrical, in the male asymmetrical. Ovisac single, borne in
front of [below] the abdomen.

I. — Genus Heterocope, Sars.

Cephalothorax T-jointed; abdomen of female three-jointed; caudal
stylets short, with three large seta3 and other small spines. Anten-
nae long, slender, 25-jointed; right male antenna geniculate, the
six joints preceding the nineteenth swollen slightly, the previous
ones coalescent; external ramus of the antennules 7-joiuted; labrum
tri-lobate; feet of the four anterior pairs with the inner rami one-
jointed; fifth feet of female with a single ramus, three-jointed, with
a terminal spine. The right foot of the male is cheliform,
four-jointed, second joint extending into a long cylindrical process,
the terminal joint with two apical claws.

The writer is familiar with but three species — H. appendiculata,
Sars, H. saliens, LiUjeborg, {= H. robusta, Sars,) and H. alpiua,
Sars. None of these have as yet been positively identified in
America* and their place seems supplied by the following genus.

II. — Genus Epischura, Forbes.

{= Scopiphora, Pickering ?)

Undoubtedly the most remarkable of fresh water copepods are
the two American species of this genus. It is not yet certain that
the second species may not be a young stage of the first but it seems
quite improbable.

Related with Heterocope, Sars. The antennas are 25-jointed,
the right of the male being geniculate. Tlie thorax is 6-jointed,
the last two segments being partially coalesced. The abdomen is
five-jointed in the male and four-jointed in the female, one branch-
ed, in the male modified for prehension. Abdomen of male with a

*Heterocope is said by Patten (Cragen) to be common at Watertown, Conn.

STATE GEOLOGIST. 131

prehensile appendage on the left side, often more or less distorted.
Inner rami of SAvimmiug feet one-jointed. Caudal stylets with
three loug setfB. The first mention of an animal of this genus
seems to be Pickering's description of Scopiphora vagans from deep
water in lake Ontario. It seems almost certain that the species so
imperfectly described in Dekay's Crustacea of New York, is none
other than a species of Epischura, but [ hesitate to substitute for
a name accompanied by good descriptions and figures, and one
which has already been incorporated, to some extent, into our
literature, one which is founded on a description so imperfect and
general that one incidental character alone enables one to guess its
application. • The following is Pickering's description:

'' Body small, eye single, near the anterior margin of the shield.
Antennae large, and as long as in the preceding genus [Cyclops],
and has the same motions in the water. Abdomen terminating
in two styles, each with three setee; last or three last joints. Ova-
ries none; legs spiny."

What is meant by the "brush" fails to appear, unless the speci-
mens were ornamented with some parasitic plants or animals.
The three setae of the caudal stylets and long antenuie will place
this form in no American genus save Epischura. But even this
statement of Pickering may be held doubtful.

Sp. 1. Epischura lacustris, Forbes.

( Plate Q. Fig. 15.)

" The scond segment of the abdomen of the male is twice as long
as the first, and produced to the right as a large, elongate, trian-
gular process, somewhat hooked backwards at the tip. The third
segment is similarly produced, but rounded and expanded at the
tip, which is roughened before and behind.

From the right side of the fourth segment arises a stout process
bearing at its apex a hatchet-shaped plate with seven broad obtuse
serratures on its anterior margin. This process is roughened be-
hind, where it is opposed to the concave side of the left ramus of
the furca. From the same side of the fifth segment, a short flat-
tened plate, of a spatulate or paddle-like form, extends forward
above or beyond the toothed process just mentioned.

The antenuEe are 25-jointed, and reach to the second segment of
the abdomen. There are especially prominent sensory hairs on the

132 TWELFTH ANNUAL REPORT.

first and third joints, borne at the tips of long spines. The anteu-
nules are short, the ramus apparently but three-jointed, the short,
median joints common in this appendage being only obscurely in-
dicated. The mandible has but seven teeth, the first simple and
acute, separated from the second by an interval about equal to the
second and third, the second to the sixth bifid, the seventh entire
and acute. The usual plumose bristle is replaced by a sharp,
simple spine.

The outer ramus of the fourth pair of legs has two teeth at the
outer tip of each of the two basal joints. The terminal joint of
this ramus is armed as follows: a short simple spine at middle of
outer margin and another at the distal outer angle; a single and
long terminal seta, strongly and sharply toothed externally and
plumose within, and four long plumose setge attached to the inner
margin.

The left leg of the fifth pair in the male, viewed from behind, has
the basal joint very large, broader than long, with the inner inferior
angle produced downwards as a long, stout, curved process or arm
as long as the two remaining joints. The second joint is trapezoid-
al, shortest within. The third joint is about half as wide at base
as the first, is straight without, with a sharp, small tooth at its
distal third, and bifid at tip. On the inner margin this joint is at
first dilated a little, and then deeply' excavated to the narrow tip,
to receive the lower end of the left leg, the lower two-thirds of this
margin forming the segment of a circle.

The right leg is two-jointed, the first joint twice as broad, enlarg-
ed at the lower end, forming an auriculate expansion at its inner
inferior angle. The second joint is conical in outline and about
two-thirds as long as the first.

The terminal bristles of the rami are very broad and strong in the
female, the outer one especially having an extraordinary size and
thickness. There is also at the outer angle of each ramus a short,
stout spine, that on the left ramus being inflated like the outer
bristle. Length .065 in.

The legs of the fifth pair in the female are three-jointed and
similar, the basal joint short and broad, the second two and one-
half times as long as wide. The leg terminates by four diverging
teeth, preceded by two others, one on each side.

Taken in the towing net abundantly in October, 1S81, at Grand
Traverse bay; also obtained rarely by Mr. B. W. Thomas, from the
city water of Chicago."

Occurring in Minnesota, probably in lake Superior.

STATE GEOLOGIST. 133

Sp. 2. Episcliura fluviatilis, Herrick.

(Plate Q. Figs. 14 and 16.)

Similar to the above but smaller (.04 iu.) The females are very-
similar, though the fifth feet are more elongate and differently
spined. The abdomen is perfectly straight and the three caudal
seta3 are of nearly equal size. The claw is armed with eight teeth,
all but the first of which are emarginate. The abdomen of the
male is straight, but has a strong process on the left side which
bears a movable claw laterally and a small second segment w4iich
terminates in two small spines. The fifth foot of the male is
peculiar; the inner ramus (or the left foot) lamelliform, one-jointed,
with two opposable claws; the right branch is simple and 3-jointed,
in form like that of the female. Here we have the most marked
difference between the two species. Found in Mulberry creek,
Cullman county, Alabama. Although a considerable number were
examined no oviferous female.^ were found, while the males contain-
ed the spermatophores and can hardly be thought immature, and,
as it is in the male that the most marked differences appear, th-e
two species seem certainly distinct.

iii.-^Genus Temora, Baird.

(Plate H. Figs. 8— 16.) '

This genus contains several marine forms and two which are
found also in streams opening into the sea. The species seem to
be as follows: T. velox, Lilljeborg, T. Jongiconiis, MneWer, {=T.
finmarchia, Baird, =Diaptomus longicaudatus, Lubbock), T.
armata, Clans, T. inermis, Boeck, and T. affinis, Poppe. T.
clausii, Hoeck, is said by Poppe to be certainly identical with T.
velox. Hoeok's figures are incomparably better than any of the
preceding, but he seems to have been misled by errors in Lilljeborg.
The species described by me before the Academy of Sciences of
Minnesota (but still unpublished) as T. gracilis, from the brackish
waters bordering the gulf of Mexico, agrees very closely with T.
affinis, Poppe. (Abhandlungen v. naturw, Vereine z. Bremen,
1880, p. 55.) This name must therefore take precedence. This
species has been found in the Rhiu?e and rivers flowing into the
gulf of Mexico, as well as in the marine or brackish waters into
which these rivers flow. The occurrence of the genus in American
fresh waters, justifies its mention here.

134 TWELFTH ANNUAL REPORT.

iv.-rGrENUS OsPBRAJs'TicuM, Forbes.

(^Potamoichetor, Herrick.)

First reported as Potamoichetor before the Minnesota Academy
of Sciences in 1879, but owing to a disastrous fire, publication was
prevented. Priority probably belongs to Forbes' name, since,
although first printed in the tenth annual of this survey, the edition
was not distributed till after the August issue of the American
Naturalist of 1882, containing the description above alluded to.
Forbes says this genus has antennas 23-jointed; all the specimens we
have gathered from Minnesota to Alabama had 24-jointed anten-
nae. The original description of ''Potamoichetor" is appended.

"Cephalothorax six-jointed, distal segments evident; abdomen,
in the male, five-jointed, in the female four-jointed; antennae
twenty-four-jointed, the right geniculated as in Ceiitropages
(=Ichthyophorbia); first pair of feet with the rami both three-
jointed, like the following; feet of the fifth pair, in the female, like
the preceding, but with a spine of the joint preceding the terminal
one enlarged and divaricated somewhat as in Centropages; in the
male, thejnght with a two-jointed outer ramus, the terminal joint
of which is spined and bears near its base a blunt expansion of its
inner margin; outer ramus of left foot three- jointed, armed with
unequal spines; inner branches smaller, similar, three-jointed; the
terminal joint bearing curved spines; ovary and testes as in Diap-
tomus, with which the mouth parts agree in the main; eyes me-
dian, confluent."

Our own experience is that the single species of this genus
prefers estuaries of running water. Forbes, however, has taken it
from swamps and wayside pools.

Sp. 1. Osplirauticuni labronectuni, Forbes.

(Plate Q2. Figs. 1—8 and 13—14.)
Potamoichetor fxicosiis, herrick, Cyclopida? of Minnesota, etc, p. 224.

"Rather slender, and in size, as well, as general appearance, re-
sembling the smaller forms ofDiaptomus; antenna rather stout,
reaching but little beyond the feet, appendaged as in Diaptomusi
in the male strongly geniculated, but somewhat variously so; the
six joints preceding the terminal four are thickened; those preced-
ing the joint or hinge are arcuate on the distal margins; the secondary
antennae are about as in Diaptomus; mandibular palp two-branched,
the outer three-jointed, the inner two-jointed; the terminal joint of

STATE GEOLOGIST. 135

the shorter branch bearing seven setae, of the other four, the proxi-
mal joint of the former with three stout spines; the maxilla? nearly
like Diaptomus; the processes have respectiveh' the following
numbers of sette: the basal plate eight, the small processes at base
of posterior branchial appendage one, the appendage itself twelve,
terminal portion three groups, first containing nine, the second
three, and the third four or five, the upper of the anterior processes
two, and the lower three; fifth feet nearly like the others in size;
the right in the male having the outer branch but two-jointed b}'
the coalescence of the tAvo outer to form an arcuate and deformed
appendage, armed at the end with three stout equal spines; corres-
ponding branch of left foot three-jointed; the terminal joint bearing
three unequal spines, each of the preceding joints only one; inner
branches similar, three-jointed; terminal joint being short and armed
with three short lanceolate sette and three longer ones, two of which
are curved so as to be slightly prehensile; fifth foot of female with
both rami three-jointed; inner ramus much smaller; antepenult
segment of the outer ramus extending into a large lanceolate pro-
cess; ova-sac long-ellipsoidal or spherical, reaching nearly to the end
of the caudal sette."

Y. — Genus Diaptomus, Westwood.

The most widely distributed and well-known of fresh water Cala-
nidae, inhabiting in various species the smallest as well as the largest
bodies of standing or sluggishly-flowing fresh water. Apparently
a recenth^ formed group whose nearest known ally is the curious
Pseudo-diaptomus, found in the gulf of Mexico. The animals of
this genus are apparently very susceptible to the influences of the
environment, and are consequently extremely variable not only in
color but in minor structural points. In America there is a curious
fact, which is susceptible of different explanations, one of which
was given in the American Naturalist at various times during the
year past. The species or varieties fall in pairs, one of which is
smaller and less highly diflerentiated, while the other is greatly en-
larged and has the peculiarities emphasized. These sets occur in
open and shallow water respectively. The large rarieties are, as
the rule, restricted te such shallow weedy pools as dry up during
summer and freeze solid in winter. The forms intermingle slightly,
but there are seasonal differences of greater or less extent.

The body is composed of an elongated thorax, with which the
head is united, forming a six-jointed cephalothorax. The abdomen

136 TWELFTH ANNUAL REPORT.

is five-jointed, though in the female these joints are so united as to
cause the abdomen to appear three-jointed. The antennae are
twenty-five-jointed, and the right male limb is modified by a coal-
escing of some of the terminal joints, a thickening of others and
the development of certain spines, hooks, and knife-like ridges to
form a prehensile organ. The first pair of feet has two-jointed
inner rami. The remainder have both rami three-jointed, save the
last. This fifth foot is difierently formed in the sexes, the inner
branch of the fifth foot being one or two-jointed. Terminal joint of
the outer ramus of this limb in the female very small or apparently
absent, second joint produced to form a stout curved claw. The left
foot is reduced in the male, serving, in some species, to afiBx the sper-
matophore to the body of the female, while the abdomen is held by
the right foot. The last segment of the thorax has one or two sharp
spines below. The spermatophore, or sperm case, is a long tube
with coagulating expansive lining, which forces out its contents on
exposure to the water. The colors are frequently brilliant.

Three or four species of this genus are known in Europe, the
first being Diaptomus castor which seems universally distributed.
It can hardly be doubted that the six forms mentioned below belong
among the varieties of this species; yet these forms can be disting-
uished very well, and are deserving of distinct names. Two other
forms are nearest D. gracilis of Sars, but sufficiently distinct. These
stand related as do the pairs of the other section, and can not be
readily distinguished.

The following is the most convenient arrangement of the genus
I have been able to devise.

Key to the Genus Diaptomus.

I. Form robust; right antenna of the male with a hook, much
swollen anterior to the geniculatiug joint.

A. Head not greaUy dilated.
* Last segment of thorax prolonged into a sharp-spined angle or tooth.
t With but one tooth (?).

1. D. castor, Jurine,
tt With two teeth.

t Length under 3 mm.

§ Inner rami of fifth feet in the female 1-jointed.

2. D. sanguineus. Forbes.
4. J>. armatus, Herrick.

§§ Inner rami 2-jointed.

3. D. minnetonka, Herrick.
, it Length over 3 mm.

\ V J/ •■;■

STATE GEOLOGIST. 137

5. D. sUigmdis, Forbes.

** Last segment of the thorax more or less united with the previous one, bearing very
small spines.

6. D. longicornis, Herrick.

(a) Length under 2 mm.
var. leptopits, Forbes.

(b) Length over 2 mm.
var. similis, Herrick .

B. Head enlarged.

7. D. laticeps, Sars •

II. Form slender, elongate; head divided into two portions; anteunte
long, slightly altered in the male.

A. Antenna of male with a book.

8. D. gracilis, Sars.

B. Antenna of ma'e without a hook.

9. D, pallidus, Herrick..

(a) Antennje much longer than the body, inner rami of fifth pair of feet in the male
1-jointed.

var. pallidiiS, Herrick.

(b) Antennse little longer than the body, inner ramus of fifth feet bi-articulate.
var. sicilis, Forbes.

Sp. 1. Diaptomus castor, Jurine. [Sars.]

"Corporis forma sat robusta. Cephalothorax in femina postice parum antice vero magis
attenuatus, angulis laminarum segmenti ultimi obtusis. Segmentvim 1-mum abdominale
absque mucrone laterali. Rami caudales brevissimi segmento antecedente \ix longiores
setis crassis et brevibus. Antennae 1-mi paris medioeris longitudinis reflexre segmentum
3-tium abdominale vix superantes, animali natante leviter arcuatse adque latera vergentes ;
articulus ultimus [?] antennae dextrte maris in hamulum exiens acuminatum. Ramus an-
tennarum 2-di paris exterior interiore parum modo longior, articulo ultimo quam antece-
dentibus 5 junctis breviore. Articulus ultimus pedum 5-ti paris in femina perrudimentaris
tuberculum solum minimum aculeo uno parvo instructum formans ; unguis intus curvatus
maximus validusque ; appendix interna indistincte bi-articulata longitudinem articuli 3-ti-
superans ; unguis terminalis pedis dextri maris longissimus leviterque arcuatus. Saccus
oviferus parva et multa continet ova colore castaneo. Color animalis variat ex fulvo, cse-
ruleo vel rubro. Longil, fem. interdum fere 3 mm. Habitat inaquis stagnantibus."

The description quoted above from Sars does not agree with
Clans' or Brady's account of the same species. From what Brady
saj's of the English Diaptomi one would conclude that the same
variations occur there as here. D. westwoodii, which he unites
with D. castor, is certainly as different from that species as our D.
stagnalis is from D. sanguineus. An actual comparison of specimens
will be necessary to clearly define the relation of the American and
European species.

C>y

138 TWELFTH ANNUAL REPORT.

Sp. 2. Diaptoiuiis saiig^uineiis, Forbes.

(Plate Q. Fig. 12.)

A species found with us in stagnating pools in early spring,
frequently following D. stagnalis and giving place to D. leptopus.
It prefers pools less foul than those affected by the latter, though
not rarely found with it temporarily. The species is quite variable,
and the variations are in directions suggestive of other species.
Measurements taken of specimens from a gathering from two
pools, one being more stagnant thafi the other, showed the follow-
ing results: — males from the less stagnant 1.7 mm.; males from the
other pool 2.0 ram.; a difference of 0.3 mm. (Males of D. stagnalis
from the latter gathering measured 3.4 mm., while the females of
that species vary between 3.8 — 3.9 mm.) Females measure about
1.8 mm. on an average, of which 1.3 mm. is the length of the thorax.
Such individuals have antennte 1.7 mm. long. The greatest width
is anterior to the middle, being about 0.5 mm.

This species differs from D. stagnalis of which, in most respects,

is a miniature, by the long antennas, short abdomen and
peculiar armature of the fifth feet.

In the female the fifth foot is about 0.5 mm. long, and the outer
ramus has two small spines on the terminal joint, while the seg-
ment before the last has a powerful toothed claw. The inner ramus
is not evidently two-jointed. The first abdominal segment is
spurred on either side. The last thoracic segment extends into a
strong angle which bears a heavy spine terminally, and a smaller
spine dorsally. On. the dorsal median line is a protuberance or
'*hump" on this segment. In the male the outer ramus of the right
foot of fifth pair is long, and terminates in a powerful curved,
toothed claw. The inner ramus is small and narrowed toward the
end; on the outside of the segment from which it springs is a blunt
spine, which is nearly as large as the ramus itself, and has been
mistaken for it. The left foot is very fleshy and its inner ramus
very rudimentary. The color is brilliant red or purple but variable.
Found in the southern states in autumn.

Sp. 3. Diaptoinus uiiunetonka, (Sp. n.)

(Plate Q. Figs. 8—10.)

A small species, smaller than either D. longicornis or D. sangui-
neus, was gathered in a pool bordering lake Minnetonka, which
contained also D. longicornis. It unites the chara2teristics of both

STATE GEOLOGIST. 139

species. The antennae reach beyond the stylets, the color is dark,
the margins of the last segment- of the thorax is rather strongly
spined, very much as in D. sanguineus. The fifth feet of the female
resemble very much those of D. leptopus, but the first segment of
the abdomen has a strong spine. The fifth foot of male resembles
that of D. sanguineus more than that of leptopus. This species
was seen but once, and no measurements can be given save that of
the male which was 1.4 mm.

Sp. 4. Diaptouius armatiis, Heirick.

Is founded upon an imperfectly known form in which the an-
tenna do not reach the end of the abdomen; the thickened part of
the male antenna? short; the antenna armed as in D. sanguineus;
the terminal claw of the fifth foot of the male with a tooth near
the base; the claw being nearly as long as the ramus.

Sp. 5. Diaptouius stag-ualis, Forbes.

(Plate Q. Figs. 11 and 13.)
D. giganteus, hekkick.

The largest species of the genus and, not improbably, too close
to D. westwoodii, Lubbock. The general characters are like those
of D. sanguineus, but the form is much more robust and the anten-
nas only moderately exceed the thorax. The proportions may be
gathered from the measurements given, In the female the length
of thorax is 2.5 mm.; abdomen 1.2 mm.; antennte 2.3 mm.; stylets
0.1 mm. The caudal stylets are as broad as long, or nearly so. The
last thoracic segment extends into an irregular process 0.1 mm.
long, bearing a spine dorsally. The first abdominal segment is
spurred on either side. The fifth feet in the female have two-jointed
inner rami. The terminal segment of the outer ramus is more than
ordinarily distinct, while the claw is biserrate. The right foot of
the fifth pair in the male is very long, its claw being strongly tooth-
ed. On the inside of the second joint from the base is a disc-like ap-
pendage peculiar to this species. The left foot is short. The longer
ramus is three-jointed, but the terminal joint is a mere curved spine,
opposing a spine from the penultimate segment, which is covered
with minute spines or teeth. The basal joint of the ramus has a brist-
ly protuberance distally. The inner ramus is marked with oblique
ridges. The right antenna has a powerful hooked spine on the
antepenult segment, the two segments beyond which coalesce in

140 TWELFTH ANNUAL REPORT.

maturity as in the other related species. For measurements see
above. Color deep opaque red or purple. Appearing in early spring
as soon as the ice is melted from the pools which it inhabits. In
the south it occurs in autumn. The name above given seems to
have the priority, although this species was figured and described
at about the same time in the annual of this survey.

Sp. 6. Diaptonius longicornis, Berrick

This name was applied somewhat loosely, the description given
being incomplete, but re-examination of types shows it to belong
unquestionably to the form since described as D. leptopus. in our
state we have found another variety, in general, almost identical
with the type specimens, but nearly twice as large. It is now
proposed to extend the significance of this name so as to include
both varieties, which will undoubtedly be found connected by
intermediate forms, thus retaining the name given by Forbes for
the variety to which it in particular applies.

(a) var. leptopus, Forbes.

This species is the commonest member of the genus in small
lakes and clear pools. It is tolerably constant in coloration, but
varies somewhat in size. The original description is insufficient to
identify the species definitely, but taken in connection with the
figure and the measurement, could hardly be refered to either of
the other American forms. This species is characterized by the
very compact thorax, the margin of the last segment of which has
two very minute spines; and by the form of the fifth feet. The
antennas reach nearly to the end of the caudal setfe, while in the
next they fall short of the length of the stylets. The outer spines
of the swimming feet are denticulate on the outer mtirgin and setose
within. The fifth feet of the female are compact, the inner ramus
is more or less obviously two-jointed; the third joint of the outer
ramus is almost obsolete and has two short spines; the claw of
second joint is strongly denticulate. The male fifth foot has a
rather long inner ramus which is very imperfectly two-jointed; the
left foot is rather long; the claw of the right foot is armed with
crenulate teeth. Length 1.5—1.7 mm., without setae. The body,
which is broadest anterior to the middle, is bluish; the tips of the
antennae are deep purple. The eggs are not as numerous as in the
next.

STATE GEOLOGIST. 141

(b) var. similis, (A"ar. n.)
(Plate Q. Figs. 5—7.)

This form is twice as large as D. leptopus, but otherwise scarcel}'
distinguishable. It occurs in autumn (and spring?) in shallow
pools, which can but be frozen solid. The following diSereuces
are the only points yet noticed. Females of both of the species
were placed side by side upon a slide and examined. D. leptopus
measured 2.4 mm., exclusive of caudal setaj; the antenna reached
hardly to the base of the stylets; the eggs measured 0.12 mm., while
those of D. longicoruis measured 0.8 mm.; the egg-sac measured
0.8 mm., while that of longicornis was 0.5 mm. A few other minute
differences were noticed, but the general form and color was iden-
tical. The peculiar doubling of the edge of the last segment is
characteristic of these two forms; each has a small spine on either
side of the abdomen. The base of the inner ramus of left foot of
fifth pair of the male has a double series of spines.

Sp. 7. Diaptoiiius laticeps, Sars.

"Cephalothorax autice dilatatus, latidudine maxima in parte antica capitis sita,
postice sensim attenuatus, segmento ultimo feminai ad latera parum extante angulis
lateralibus acuniinatis. Segmeutuni 1-muiu abdominale femina; antice latum mucrone
brevl laterall arniatum, postice sensim attenuatum. Rami caudales sat magnl seg-
menta antecentia 2iuncta longitudluetv<luantes sells brevlsslmis et robustis instructl.
Antennae 1-mi parls femlnse longltudinem corporis requantes, anlmall natante rectse et
quam In D. graclll adliuc magis postice vergentes ; artlculus autepenultimus antennoe
dextraj maris liamulo armatus. Ramus exterior antennarum 2-dl paris interlore multo
longlor articulo ultimo longltudinem articulorum anticedeutlum 5 ajquante. Pedum
5-tl parls femlnse artlculus ultimus parvus, cylindricus, non vero tam rudimentaris
quara in D. castore, aculeouuo brevl apicall Instructus ; appendix interna ne tertiam
quldem longltudlnls articull 3-tl partem oequans et unlartlculata ; pedis dextri maris
artlculus 3-tIus extrorsum aculeo forcl armatus, ungue termlnall valde flexuoso et sub-
slgmoides ; sinister aculels duobus rectis terminatus. Saccus oviferus sat multa conti-
netova. Color pleurumque isete caeruleus, Interdum pallldior, albescens. Longlt.
femlnse clrcit. l'/^ mm."

Sp. 8. Diaptomus gracilis, Sars.

"Corpus quam in D. castore gracilius, ceplialotliorace et antice et postice attenuato,
latltudlne maxima In medio slta. Angull laminarum segmentl ultlml thoracalls feml-
nse in mucrones teuues et acumiuatos producti, et mucrone simili sat magno segmen-
tum 1-mum abdominale utrinque armatus est. Rami abdomlnales breves setis in fe-
mlna valde dlvergentlbus. Antenna;^ l-mi paris femlna? perlongse et tenues, longltudi-
nem totius animalis longe superantes, anlmall natantl recta et aliquantum postice ver-
gentes ; artlculus autepenultimus antenua dextra^ maris bamulo longlor, articulo ultuno
rami dimidlum longltudinem a?quante. Pedum 5-tl parls femina; articulus ultimus rii-
stlnctus, quadratus aculels duobus aplcalibus quorum interior aplcem fere unguis arti-
cull penultlmi attiugit instructus ; appendix interna articulo 3-tlo brevior ; unguis ter-
minalls pedis dextri maris aplcem versus valde curvatus. Saccus oviferus semper ova
continet pauclsslma et magua regularlterque distrlbuta. Animal pleurumque pellucl-

142 TWELFTH ANNUAL REPORT.

dum colore albido, iuterdam vero facia transversa lata coloris fusci saturati in medio
cephalothorace ornatum. Longit. femiute parum supra 1 mm."

The two forms following are suflBcieiitly distinct fro n the above
and form a closer link with the marine Calanidfe. It is doubtful if
any absolute line of demarkation exists between these varieties,
although they are here distinguished.

Sp. 9. Diaptomus pallidns, Herrick.
( Plate Q. Fig. 17.)

Length 1.20 mm.; length of antennse 1.35 mm. Colorless. Head
separated by a suture into two parts; form very slender. Antennae
with elongated sette, which are very plumose. The right male an-
tenna has no hook. The inner rami of the fifth feet are one-jointed
in both sexes. Left foot of the fifth pair of the male of peculiar
form (see plate Q, fig. 17, for an extreme instance). Entire Missis-
sippi valley.

var. sicilis, Forbes.

(Plate Q. Fig. 18.)

Like the above, but larger. Length 1.1:5 mm. Length of an-
tennas 1.5 mm. Inner ramus of male feet of fifth pair two-jointed,
those of the female one-jointed. The fori;n of feet varies a little
from the above. This species has been but once encountered in
Minnesota, the previous species occurring abundantly in our larger
lakes.

D. kentuckyensis. Chambers, is referable to one of the above species, probably D.
longicornis.

For a full account of synonymy see Rehberg, Beltrag z. Kenn.d.freile'b, Suesswasser
Copepoden, p. 552.

VI. — Genus Lim:nocalanus, Sars.

Cephalothorax 6-jointed, slender; abdomen in the female 3-
jointed, in the male 5-jointed. Antennae shorter than the body,
25-joiuted. Caudal stylets long. Feet of the four anterior pairs
with both rami 3-jointed; external ramus of the fifth foot in the
female 3-jointed, second joint produced into a spine ; inner rami
3-jointed in both sexes and like those of the previous pairs; external
rami 2-jointed in the male, the right and left dissimilar.

STATE GEOLOGIST. 143

Sp. 1. Limnocalauiis iiiacruriis, Sais.

A species similar to L. macrurus has been fouud in lake Michigan,
and probably occurs also in this state in lake Superior. We can
do no better than quote Sars' description.

"Corpus gracile et angustatiim. Cephalothorax supra vlsus elongate ovatus, latitu-
dine maxima in medio sita antiee et postice jeiiualiter atteauatus. Caput annulum
unicum priebens, a latere visum parte antica altiore et coavexa slnu distincto a poster-
iore disjuncta, margine antico oblique descendente. Segmentum ultimum thoracis par-
vum neque ad latera extans in femina et mare simile. Abdomen sub-cylindricum tbor-
ace longius. Kami caudales valde elougati et angustati tertium longitudinis abdominis
partem superantes, supra et ad latera spiuulis vel pUis brevibus obsiti, intus ciliati,
setis 5 majoribus uniarticulatis et ciliatis, quarum 2-da ab interiore uumerata omnium
longissima ceterfeque extus graduatim longitundine decrescentes, exteriore ceteris
minore absque apice sat nmota ; seta adest prreterea alia intus adfixa ut in geueribus
antecedentibus tenuissiraa et simplex. Frons a latere visa obtuse acuminata appeudio-
ibus tentaculiformibus duabus perbrevibusinstructa. Antennae 1-mi paris reflexoe seg-
mentum penultimum abdominis minime attingentes, articulo ultimo setis 5, quarum
posteriores 2 longissimce, instructo, articulis anteceoentibus 3 setae simili postice ver-
gente prasditis ; dextra maris articulatione inter articulum 18-mum et 19-mum geniculans.
Anteunarum 2-di paris ramus exterior interiore et longior et latior, 7-articulatus, arti-
culo 2-do omnium maximo, sequentibus i minimis junctis articulo ultimo brevioribus
setisque longissimis instructis. Mandibulje ad extremitatem inferiorem in dentes ex-
euntes 9, quorum exteriores 2 ceteris majores, interiores 2 tenues et setiferes sunt ; pal-
pus longus et angustatus 3-articulatus, articulis ultimis 2 brevissimis, ramo exteriore,
vel aupendice brancliiale, parvo. Maxillte l-mi paris eadem fere structura ac in Diap-
tomo. Maxilloe 2-di paris validissimas 8-articulatje, articulis ultimis 5 in ungues exeun-
tibus longissimos et fortlssimos margine altero sparsim pilosos, ad apicem falcatum
vero nudos vel aculeispersubtile et dense obsitos ; 3-tii paris [Maxillipedes] valde elon-
gatte et angustatae antiee vergentes articulis 7 setis pleurumque longis prcedltis compo-
sita?. Pedes omues biramosi natatorii, ultimo pari in mare bi-articuiatus in pede dex-
tro et sinistro dissimilis, articulo ultimo in illo brevi etrobusto ad apicem quasi trun-
cato dentibusque 3 parvis et obtusis armato intus vero in aculeum magnum et validum
excurrente. in hoc valde elongate extus et ad apicem aculeato intus vero nudo. Genius
unicus propius raarginem inferiorem capitis situs. Animal quamquam pelluciuissimus
et fere omnino hyalinum, facile tamen accumulatione in thorace sat magna liquoris
oleosi Is-re fu'.vo-rubide colorati se prodit. Longit. circit. 2Vk mm."

FAMILY CYCLOPID^.

Contains five genera, viz: ThorelUa, C^jclops, Oithona, Lopho-
pJwnts and Cijclojnna; passing, by the genera Misophria and Pseit-
dO'Cijclops, into the Calanidai or marine copepods. The affinities of
these little known genera need further study, as they are very in-
teresting, the question being still open in how far the cyclopoid
forms are altered by adaptation to saline habitat, if such an adapta-
tion takes place at all.

Cephalothorax ovate and usually much more robust than the
abdomen; anterior antennae seldom longer than the cephalothorax,
those of the male alike on both sides and modified for the purpose
of clasping; posterior antennas unbranched (i. e. palpus wanting);

144: TWELFTH ANNUAL REPORT.

palps of maudibles and maxillae usually well-developed; foot-jaws
mostly less developed than in Calcmidre; first four pairs of feet as
in CalcDiiche, Mth pair rudimentary, alike in both sexes, and usually
one- or two-jointed; ovisacs two.

The circulatory system of this family is partly lacunal and has
been thought to be entirely so in the genus Cyclops, closer obser-
vation, however, shows that there is something like an imperfect
central organ at the point occupied by the heart of higher Cope-
pods. This was figured in my previous report, plate V, fig. 1, but
no mention was made of the discovery. It has since been verified.
The apparatus referred to is a modification of that described under
Canthocamptus. In the second thoracic segment there is a set of
swaying membranes which constitute a valvular apparatus, chiefly
moved by the action of the stomach.

Genus Cyclops.

The sole representative of the genera of the Cyclopidge here treated
is the best known of the Copepoda. Every one is familiar with the
'' common cyclops," but few realize how many are the species in-
cluded under this name. An attempt is here made to enable the
student to recognize the more obvious distinctions upon which the
genus is subdivided and to identify such of the species as seem valid
and at the same time recognizable withoutreconditestudy of devel-
opment. Without attempting a complete elucidation of the syn-
onym}', which is practically an impossibility, a proximate classifica-
tion of all the species known to me is attempted. Thirty sufiici-
ently well marked species are enumerated, and the position of a
number more is indicated.

Aiiteuiife 18-jomtecl.

Sp. 1 . Cyclops elong-atus, Glaus.

This species, cited hitherto, apparently, by but one other author
than Clans,. is distinguished from the C. pulchellus group by the
IS-jointed antenna, Avhich are hardly longer than the first thoracic
segment. The caudal stylets are longer than the two preceeding ab-
dominal segments, and bear rather short setae. C elongatus has
been found by Cragin near Cambridge. That this species, found
thus far by but a single author in Europe, appears in America, may
serve as a warning not to decide too hastily from its habitat that a
copepod is new.

STATE GEOLOGIST. 145

Antenuse IT-jointed.

I. — Fifth Foot 1-jointed.
Sp. 3. Cyclops ater, Herrick.

{Plate Q^. Figs. 9— 12.)

This is our most striking species and loves the clearer flowing
waters. The thorax is broadly oval and, usually, of a deep color.
Antennae as long as the cephalothorax (1.2 mm.), slender, and

tapering toward the end; formula ^ — :=:- -__~-.^^s^r:r-^ ;

last three joints rather short, the last joint furnished with an
unserrated knife-like ridge as in C. tenuicornis; maxillipedes
rather large; fifth foot cne-jointed, armed with three subequal
spines; abdomen rather short, last segment especially short;;
stylets of moderate length; setae rather short, internal seta much
longer than the outer, lateral seta near the end of the stylet;
eggs pale. Color deep blue or gray. Length 2.1 mm. The young^
can be recognized without a glass by the band of deep color which
crosses the thorax in the middle.

Collected near Minneapolis, in '' Mud lake " and Bassett's creek.^
This species has been collected in different parts of the Mississippi
valley from Alabama to Minnesota, but is nowhere very abundant^
being but rather more so southwardly.

II. — Fifth Foot 2-jointed.
A. — First joint of fifth foot very broad.

Sp. 3. Cyclops viridis, Jurine. (Rehberg.)

(var. a.)

C. vulgaris, koch, fischf.r, saks.

C. Tjrericorni", clals, lubuock, hellek, fric, hoek.

C. viridis, CRAGiy.
(var. b.)

C. gigci^, claxjs, sars, fric, brady.

C. ilioens, HERRICK.

The American form is usually somewhat different from the C.
gigas, but the stage prior to maturity is like that figured by Brady.
Observations made over a considerable territory and for a period of
several years led me to the conclusion expressed by Rehberg (Ab-

1 The accent marks are usefl to signify that joints represented by them (counting
from base) are either long—, sliort w or medium :=:,

10

146 TWELFTH ANNUAL REPORT.

handl. naturwiss. Vereine zu Bremen. Bd. vii, 1. Heft, p. 62)
that C. gigas is but a greatly enlarged form of C. brevicornis. See
also American Naturalist, May, 1883, p, 491^ where I have expressed
a similar opinion regarding the American form.

A part of the original description of C. iugeus is here given.

Thorax large; abdomen rather slender; stylets slender, with the
lateral seta well towards the end; second and third setae alone long,
weakly pectinate; last joint but one of abdomen sometimes toothed
along the distal, under margin; jaws with large teeth; antennee very
short, not reaching to the base of the first cephalothoracic segment;
formula — i::— — ir^-^ — w-^w^v^^-^^rr; ftfth foot two-jointed, the
proximal joint very broad with a strong spine; second joint C3'lindri-
cal with a long seta and a very short spine near the end; oper-
culum vulvas somewhat heart-shaped; egg-sacs oval-elongated,
reaching beyond the end of abdomen; length 4 mm., including
stylets and setae.

Sp. 4, Cyclops leiickartii, Claus.
? C. crassvLS, fischee.

Is said to be elongated and slender; the antennae are nearly as
long as the first three segments. The fifth foot is like the smaller
forms of the above, but the second joint has only one spine. The
proportions of the caudal setae are very much as in the above.

Rehberg denies that Sars' identification of this species so briefly
described by Claus is correct; his description is therefore copied.
Sars refers also with a query to C. obsoletus, Koch.

"Cephalothorax ovatus autice sat attenuatus, fronte leviter truncata, secmento ulti-
mo parvo vlxque ad lateia exstante. Segmeutum abdominale l-nium sub-cylindricum
aiitlce quam postice parum latins. Rami caudalisbrevisculi longitudinemsegmeutorum
antecedentium duorum non attiugentes setis apicalibus sat lougis, externa furcae
longitudinem soquante dimidiamque Interni, intermediaium interiore altera aliquauto
longiore longitudinem abdominis fere requante ; seta niarginis exterioris ab apice sat
teniota. Antennse ]-mi paris IT-articulatpe, longiE et apicem versus attenuatse,
reflexBC segmentum i-tum corporis fere attingentes ; 2-di pans quam in speciebus
ceteris longiores. Maxillarum 2-di paris margo posticus subtillssime crenulatus. Pedes
5-ti paris bi-artlculati, articulo ultimo bisetoso. Rami pedum natatoriorum omnes 3-ar-
ticulati ; articulus rami exterioris intus setis 3, extus aculeis 2 instructus. Lamina par-
tes basales pedum 4-ti paris conjugens utrinque in processum acuminatum exit. Rami
Interioris articulus ultimus insolito modo in longitudinem extensus in pedibus 4-ti paris
aculeis apicalibus 2 subajqualibus armatus. Saccioviferi rotunda to-ovati ab abdomine
sat exstantes. Longit. parum supra 1 mm."

Sp. 5. Cyclops lacustris, Sars.

Cephalothorax sub-ovate, truncate in front. Abdomen nearly

STATE GEOLOGIST. 147

of equal width; caudal stylets longer Ihaa the last two seg-
ments of the abdomen terminal; setee of moderate size, inner
three times as long as outer, internal pair nearly equal. Antennae
as long as first two segments. The inner ramus of fourth foot has
the exterior thorn very small. The second joint of the fifth foot is
small and the external thorn very small. Length 1.5 mm.
Not seen in America.

B. — First joint offfthfoot of moderate size.

(a) Terminal segment of fifth foot with one long seta and a
short thorn.

These small species pass into the above group and constitute one
of the most difficult groups of the genus. The distinctions offered
are very small and specific variation considerable.

Sp. 6. Cyclops strenuus, Fischer.

3 C. pictus, KOCH.

C. brevicaudatus, claus, lubbock, heller, fric.

C. strenuus, sars, brady.

Antennge reaching about to the end of the third segment; caudal
stylets slender, three times as long as the last segment; the outer of
the caudal sefffi shortest. The third seta is over once and one half
the length of the stylet.

Sp. 7. Cyclops lucidiilus, Koch.

C. lUCiduJw^ SARS.

C. furcifer, claus.
C. vernali>; Fischer.

This species is given on the authority of Rehberg. Claus con-
sidered C. furcifer a large variety of the above species.

The antennae are as long as the first segment; the fifth foot is
peculiar in form, with the second joint armed with a spine and a
hook; length 1.3 mm.

Neither this nor the previous species is known in America.*

Sp. 8. Cyclops robustiis, Sars.

Antennse shorter than first segment, thick. Body depressed,
first segment broad and rounded anteriorly, the others spreading;
caudal stylets nearly parallel, long; inner median seta much the

*C. palchellus, Brady Is not C. pu'chellus, Kocb, and may be tbe above species.

148 TWELFTH ANNUAL REPORT.

longer, external setae very short. Terminal joint of outer rami
with three spines externally and four setae internally. Length 1.3-
mm. I know nothing of this species save the description of Sars,.
a part of which is quoted above.

Sp. O. Cyclops parens, Henick.

(Plate R. Fig. 22.)
Cyclops parcus, herrick, Crustacea of Minnesota, p. 229 ; Plate VI., Figs. 12—15.

In form and general appearance greatly resembling Cyclops
thomasi, which it nearly equals in size. The chief differences are-
found in the length of the caudal stylets and antennge and in the
form of the fifth foot. The antennae are shorter than, or about as
long as, the first thoracic segment. The formula expressing the
length of the joints corresponds with that for C. thomasi. The
antennules are shortish. The labrum is rather narrow, projecting
below into obtuse angles, the middle of the lower face being occu-
pied with nine rather small teeth. The terminal joint of the larger
branch of the maxilliped bears four hairs. The second joint has a
moderately large dactyl, the movable finger of which is small and
sparsely spiny, the immovable finger is ornamented by an oblique
series of blunt prominences and a small seta at its base. The first
pair of feet has two terminal and two interior set« and two exter-
nal spines on the ultimate joint of the outer ramus, while the cor-
responding joint of the inner ramus bears one inner seta and large
spine and three outer setee. The fourth foot has, in the first case,
two outer spines, a terminal spine and seta and three internal setas,
and, in the second, one external seta, two subequal terminal spiaes
and two internal setae. The fifth foot is two-jointed, bearing on
the short basal joint a moderate seta and on the larger second joint
a considerable seta and a small oval spine on its side. The caudal
stylets are short and the lateral seta is near the end (about 1-5).
The outer seta is but three- fourths the length of the inner. The
inner of the median setas is considerably longer than the outer.
The shape of the operculum of the female is very characteristic, it
being nearly oval. The last two joints of the thorax are acute.
The entire length is about 1.5 mm.

Sp. lO. Cyclops brevisplnosiis. (Sp. e.)

(Plate S. Figs. 7— 11.)
The form for which this name is proposed takes the place of the

STATE GEOLOGIST. 149

above in the larger lakes. It appears to be but a modified condi-
tion of the above species, from which it differs iu its slender form
and especially in the very slender caudal stylets. The outer caudal
seta is reduced to a short ciliate thorn. The fourth foot is also
modified by the great enlargement of the spines and the reduction
of the sette. The number of the setae is the same, but they are
•differently disposed. The form of the operculum vulvae is also
slightly different.

(?) Sp. 11. Cyclops uniangulatus, Cragin.

Cyclo}is uniani/ulatm, Cragin. A Contribution to the History of Fresh-water Cope-
pocia, p. 6.

Cragin was not conversant with the description of C. parcus, witli
Avhich his description agrees save in one point. It differs from C.
parcus in having three inner setae on the terminal joint of the outer
ramus of the first foot. It would be officious to suggest a possible
oversight here, but C. parcus has only two in type specimens
((though iu all this group the corresponding ramus of the second
Joot has three setae), so that at present the two must be kept dis-
tinct.

Sp. 12. Cyclops sciitifer, Sars.

Not having identified this and the following species it will be
best to quote the descriptions.

C. strenuo affinis. Cephalothorax sat elongatus, segmentis ultimis duobus in femina
ad latere valde promineutibus iiique processes exeuntibus laminares et hyalinos utrin-
•que inter se contiguos, quare thoracis pars posterior tamquam clypeo fornicato quad-
rangular! obtecta esse videtur. Segmentum l-mum abdomiuale ad basin valde dilata-
tum latitudine quam ad marginem posteriorem duplo niajore. Rami caudaies segnien-
tesantecedentlbusduobus juuctis parum longiores. introrsum clliati, setis apicalibus
brevisshnis, intermediarum interiore ceteris multo longiore. Antennse 1-nii paris 17-
articulatse, reflex^e segmentum 2-dum corporis superautes setis plurumque longis obsi-
ta?. Pedum structura eidem in C. strenuo similis. Articulus scilicet ultimus rami exter-
ioris pedum natatoriorum setis 5 instructus in paribus anterioribus duobus 3, insequen-
tibus duobus 2 modo aculeis marginis exterioriis armatus ; aculeorum apicalium
rami interiores pedum 4-ti paris exterior brevis et rudimentaris. Pedum 5-ti paris arti-
culus ultimus sat magnus artlculo basali parum minor extrorsum sparsim pilosus in-
trorsum aculeo armatus ciliato setaque longa terminali. Sacci oviferi parvi globosl
abdomen magna ex parte obtegentes. Longit. circit. 1}4 mm.

Sp. 13. Cyclops al>yssoruin, Sars.

C. strenuo et scutifero sat affluis. Cephalothorax ovatus antice obtuse truneatus. seg-
mentis parum ad latera extantibus. Rami caudaies longi et tenues satisque divergen-
4es, longitudinem segmentornm antecedentium 3 superantes, setis apicalibus longioribus
intermediarum interiore duplam longitudinem furcre superante, exteriore quam ilia
.parum breviore. Antennae i-mi paris l7-articulatse longaj et fere rectte distincte posticl

150 TWELFTH ANNUAL REPORT.

vergentes, reflexa^- segmentum 3-tium corporis fere attingentes. Pedum natatoriorun*
structura fereeadein ac in speciebus aiitecedentibus ; aculeorumapicaliuni rami interi-
oris pedum 4-ti paris exterior dimidiam fere interioris attingens longitudine. Pedum
5-ti paris articulus basalis minimus ultimo multo brevier parumque latior. Sacci ovl-
leri mediocres rotundato-ovales abdominique appressi. Lougit. circit. 2 mm.

(b) Terminal segment of fifth foot with two rather long setae.
* External and internal caudal setae not extremely short.

Sp. 14. Cyclops oithonoicles, Sars.

(Plate S. Figs. 2—6.)

f C. hyalinus, rehberg.
f U. tenuissimus, hekrick.

This most interesting species occurs under peculiar circumstances.
It is perhaps the rarest member of the genus and seems, beyond a
doubt, nocturnal in its habits. It was first found by Sars in saline
water and named, on account of its slender form, from the marine
Oithona. A similar species which, though about half as large, is
hardly distinct, was found by Rehberg near Bremen. Rehberg men-
tions particularly that it was found oftener at night than during
the day. In America a similar species was described from near
Paducah, Ky., under the name C. tenuissimus; but the possibility of
identity with the Scandinavian species seemed excluded by the
habitat. A gathering taken at night from one of the lakes near
Minneapolis contained a few specimens of similar characters, and
there no longer seems to be a doubt of the identity or very close
relation between these forms.

The antennas are longer than described for C. tenuissimus, nearly
equalling the thorax. The last joint of the antennae is short, but
the toothed character was not noted. The fifth feet are small, the
spines are very long and slender. The margins of the abdominal
segments are irregularly toothed. The species will be confused
with no other. It is marked with blue in spots. Length 0. 5 — 1.
mm.

Sp, 15. Cyclops simplex, Poggenpol.

Cyclops Leeuwenhoeku, hoek (fide Rebberg).

This species is of more compact form than the last, which it re-
sembles in the form of the caudal stylets and the fifth foot. The
antennae are nearly as long as the thorax, the last two joints being
elongate and having a knife-like ridge which has at the end teeth
like those figured in C. tenuissimus. Length 1. — 2. mm.

STATE GEOLOGIST. 151

** The two median setse much longer than the external.

The species of this section are the most perplexing of the genus.
The best that I can now do is to indicate the relations of the nom-
inal species and express the conviction that most are of varietal
value simply.

Sp. 1<>. Cyclops piilchelliis, Koch.

- C. bicuspidahts, CLAUS. -

t Terminal joint of outer ramus of feet witli two spines outwardly.
16 a. C. iliomasi, Forbes.
16 b. C navus, Herrick.
tt W'ith three spines.
16 c. C. bisctosus, Reliberg.

-= C. bicusjiidatus, Sars.
= (?) C. insectus, Forbes.

There are at least three well marked varieties in America, which
may probably rank as species and have been ranked as such by
Forbes. I give verbatim Forbes' description.

(16a) Cyclops tliomasi, Forbes.

(Plate U. Figs. 4, 5, 7 and 8.)

"Elongate, slender, broadest in front and tapering backward,
antennae 17-jointed, reaching the middle of the third segment.

The first abdominal segment in the female is broad in front and
slightly emarginate on each side before the anterior angles, and the
last segment has a terminal circlet of small spines. The rami of
the furca are more than half as long' as the abdomen, and each bears
two short rows of transverse spinules outside, one at the anterior
the other at the posterior third. With the latter a spine occurs
about as long as the outer terminal seta. The inner seta at the tip
of the ramus is about half the length of the furca, the outer still
shorter. The inner median seta is as long as the abdomen and
furca, and the outer about half as long.

In the outer ramus of the first pair of legs the terminal joint
has one spine and two setee at the tip, one spine on the outer mar-
gin and two set^ within.

In the second, third and fourth pairs the last joint lias one spine
and one seta at tip, two spines externally and two setse within.
The inner rami of the second and third pairs terminate in one spine
and one seta, that of the fourth pair in two spines, the inner of
which is only half as long as the other.

The legs of the fifth pair are two-jointed, with the basal joint

152 TWELFTH ANNUAL REPORT.

quadrate, broad, and bearing one long spine. The second joint is
narrow and longer, parallel and truncate, with one terminal spine
about equal to the preceding, and one about half that length.

From C. hicuspidatus, Claus, this species may be distinguished
by the armature of the outer ramus of the first pair of legs, and
from C. bisetostis, Rehberg, by the armature of the outer rami of
the other legs.

It shares with Diaptomus sicilis the responsibility of affording
to the young white-fish their earliest food."

(16 c) Cyclops iusectus, Forbes.

(Plate U. Fig. 9.)

"Closely allied to the preceding, but more robust in all its parts,
and with the second cephalothoracic segment widest. The abdo-
minal segments are all bordered with spinules posteriorly. The
two median caudal setae are much more nearly equal than in tho-
masi, the outer and the inner are very short, but longer than in
that species. The inner in our specimens is longer than the outer
— the reverse being the case in hicuspidatus as described by Claus.

"The legs are armed nearly as in thomasi, but the last joint of
the outer ramus of the first pair has two spines externally besides
the one at the tip, and the terminal spines on the last segment of
the inner ramus of the fourth pair of legs are about equal."

Both forms probably occur in Minnesota, though the second has
been seen but once, and the identification lacks confirmation. The
differences between the two are almost exactly those prevailing
between C. hicuspidatus (== pulchellus) and C. bisetosus, Reh., if
I correctly understand Sars. Claus" description does not agree
with that of Sars. Further study of the European types will be
necessary before a satisfactory settlement can be reached.

(16 b) Cyclops navus, Herrick.

Cyclops navus, herbick, Copepodaof Minnesota, p. 279.

This name, proposed at nearly the same time as C. thomasi, ap-
plies to a very closely related form which I can but regard as a
variety of that species. It seems constant in its differential char-
racters in given localities, but we are now familiar enough with
the fact that changed conditions in the water occasion changes in
forms in the copepods.

This form inhabits shallow pools. It is larger than C. thomasi,

STATE GEOLOGIST. 153

has much shorter stylets and differently proportioned antennae, etc.

Length 1.5 ram. Thorax 0.9 mm.; abdomen 0.6 mm.; stylets
<0.14 mm,; last two abdominal segments 0.16 mm.; antennae 0.7 mm.;
first segment of body 0.5 mm. The basal segment of the antennae
is long and ornamented with several transverse series of spines, the
last two segments are equal and longer than tlie preceding. The
armature of the first and fourth feet is identical with C. thoma-i, as is
the form of the female openings and the fifth feet. The form of
the first feet, candal stylets and other details were correctly figured
on plate V of the Cyclopidae of Minnesota.

Specimens of Cyclops piilchellas (thomasi) were obtained from a
•cistern which is supplied solely by rain-water. The eggs must have
been introduced in ice which had been placed in the cistern at least
a year previously. The cistern is entirely dark, so that these ani-
mals must have been deprived of light for many generations. The
general color was of course very white; the eye spots were pale, but
present with some pigment and the lenses. No noticeable altera-
iion in form had resulted.

(c) Terminal segment of fifth foot with three setae.
Sp. 17. Cycloijs teniiicornis, Claus.

(Plate R. Fig. 16.)
■var. a. Knife-like ridge upon tlie antennae smooth.

L. albidllS, JUKINE,

C. quadricornis, var. h, baird.

C. tenuicornis, saks .lubbock, heller, fric,uljanin, hoek, brady, herrick.
C claii^ii, roGGENPOL.
C. annulicorais, sars.
var. b. Knife-like ridge of antenna; toothed.
C. obesicornis, templeton.
C. sigfiatus, koch, sars, ul.ianin, krady.
C. coronatus, claus, i.ubbock, heller, fric, hoek.
C. signatus, var. fasciacornis, cragin.

Cyclops tenuicornis, as thus comprehended, is widely distributed
and variable. European specimens in our collection have longer
stylets, but seem otherwise identical. The nearest relation is C.
ater, which is easily distinguished by the compact oval form of the
thorax and the one-jointed fifth foot. In the stage previous to
maturity the ''signatus" form has no teeth upon the ridge of the
last segment of the antennae; it is then similar to the C. tenuicornis.

Cephalothorax broad; abdomen rather slender; antennae reaching
-about to base of thorax, attenuated at the end; terminal joint with

a knife-like ridge; formula— -^ — r---^---ww^ ; fifth

foot composed of a long basal joint bearing a long spine and a ter-

154 TWELFTH ANNUAL REPORT.

minal three-spined division; caudal stylets twice as long as last ab-
dominal segment; setse all nearly terminal, inner one long. Length
2.5 ram.

Common in America, England, continental Europe, etc. C. clau-
sii, Poggenpol, is known to me only from the citations of Rehberg
and the translation given by Cragin, hence I can not judge authori-
tatively of its validity. Certain points in the translation are obvi-
ously erroneous, as where the larger branch of the fifth foot is spoken
of. No distinctions sufficiently clear to enable us to separate it
from C. tenuicornis can be gathered.

III. — Fifth Foot 3-jointed.
(See Cyclops modestus.)

Aiiteniioe 10- jointed.

There are a few forms which, although they might more properly
be ranked with the previous section, seem rarely or never to acquire
more than sixteen joints.

Sp. 18. Cycloii^ lang-viiclus, Sais.

Thorax attenuated posteriorly, caudal stylets exceeding in length
the two preceding segments, internal seta short, half as long as the
outer, the inner of the median setae as long as the abdomen. Both
rami of the first foot and the inner of the second are two-jointed.
Second joint of the fifth feet sub-linear, armed with a seta and a
spine. The fact that some of the feet have two-jointed rami sug-
gests a young stage of some other forms.
• This species has not been seen in America.

Sp. 1$>. Cyclops modestus, Henick.

(Plate R. Figs. 1—5.)

American Naturalist, 1883, p. 500 (May).

This small species, 1.0 mm. long, was first recognized in Cullman
county, Alabama, but occurs also in our lakes. The color varies, but
very characteristic is the peculiar shining or glaucous surface of the
strongly arched thoracic shield and the evenly curved segments of
the abdomen. The antenna reach but little beyond the very long
first segment; the)'' are usually 16-jointed, but I have notes of a
similar form in which the antennae are 17- jointed. The feet are

STATE GEOLOGIST. 155

all 3-jointed and are peculiar in their armature. The fifth foot is
obscurely 3-jointed, the second joint bearing a short spine and the
terminal joint two spines of varying length. The stylets are once
and a half as long as the last segment and are peculiarly excavated
for more than the lower third, from the point where the lateral
spine is situated. The outer terminal seta is short, the others being
sub-equal and also short. The opening of thespermatheca is elong-
ated, oval. The antenna of the male is divisible into five regions,
the third being formed by the thickening and coalescing of four or
more segments.

Antennae 14:-jointed.

Sp. 20. Cyclops insignis, Glaus.

The two forms here belonging might be considered atavic varie-
ties of Cyclops pulchellus. Brady's figures and description of his
C. insignis (= C, lubbockii) agree almost exactly with what Reh-
berg says of Cyclops helgolandicus (Abh. v. naturw. Vereine zu
Bremen, vii. 1, pp. 62 — 64). Rehberg regards that species as an
atavic sub-species or variety of C. pulchellus. With C. insignis,
Claus, the case seems to be different. The occurrence of this species
is not conditioned by marine influence. I found it abundant about
Leipzig, Saxony. The differences between it and the C. insignis of
Brady are, as the latter says, very slight. Figs. 11 — li of plate T
are drawn from Leipzig specimens, from osmic acid preparations.
The first foot, outer ramus, has three external spines on the distal
segment, two setae at the end, and three within; the inner ramus
has one internal seta, a spine and a seta terminally, and three ex-
ternal setae on the distal segment. The outer terminal segment of
the fourth foot is like the first; the inner one has only two external
setfe. The external setie of t4ie caudal stylets exceed half the length
of the stylet and are pectinate. The fifth foot has a short basal
joint armed with a single seta, the second joint being slender and
armed with two unequal setae. The gathering above mentioned,
taken near Leipzig, Dec, 1881, contained scarcely a female among
scores of males in various stages of development. This is so con-
trary to what is expected that, notwithstanding the apparently
good characters on which the species is founded, an uncertainly
exists in the mind of the writer as to the permanent adult charac-
ters of this species.

156 TWELFTH ANNUAL REPORT.

AnteniifB 12-joiiitecl.

*

I. — Fifth Foot 2-jointed.

A. — Terminal segment of fifth foot ivith. a seta and a small spine,

Sp. 21. Cyclops capillatus, Sars.

*'CepliaIothorax sub-ovate; anteriorly uniformly rounded; seg-
ments projecting somewhat laterally, the last being scarcely wider
than the first abdominal segment. Abdomen attenuated posteriorly;
caudal rami almost as long as the last three abdominal segments,
hardly divergent, the external and internal apical seta3 short and
nearly equal; the interior of the median setee as long as the abdo-
men; lateral seta about in the middle of the stylet. Antennae of
the first pair robust, slightly exceeding the first segment of the
body when reflexed, v/ith the twelve joints densely covered with long
and divergent hairs. The last joint of the outer rami of swimming
feet are elongated and armed externally with three spines, internally
with four setse; the interior apical spine of the interior rami of the
fourth pair of feet longer than the exterior. Feet of the fifth pair
large, with a large and thick basal segment and a small oval second
joint bearing one long seta and a short spine. Ova-sacs small, nar-
row and divergent. Eye very small. Length nearly 2 mm."

Very close to C. viridis in many points. Found only in Scan-
dinavia.

Sp. 22. Cyclops crassicaudis, Sars.

Cephalothorax elongate-ovate; segments produced laterally, espe-
cially the last, which extends into a somewhat procurved process.
Abdomen short and thick, first segment somewhat excavated; caudal
rami equalling the la^t two segments of the abdomen. External
apical seta longer than the internal, both short; median setse long.
Antennge of the first pair 12-jointed, scarcely longer than the first
segment. Swimming feet short and thick, spines and seta3 short;
the interior apical spine of the last joint of the inner ramus of the
fourth foot almost twice as long as the exterior spine. Terminal
joint of the fifth foot small, armed with a spine and a seta; seta of
the basal segment short. Ova-sacs oval, somewhat divergent.
Length 0.75 mm.

Found only in Scandinavia.

STATE GEOLOGIST. 157

II. — Fifth Foot 1- join ted.
Sp. 23. Cyclops varicans, Sais.

"Cephalothorax ovate, attenuated about equally in front and be-
hind, with the last segment wider than the abdominal segments,
produced laterally and bearing a long seta. Abdomen elongate;
caudal rami scarcely as long as last two segments; the internal
apical seta twice as long as the outer; median pair elongated, the
internal one as long as the abdomen. Antennae 12-joiuted, robust,
shorter than the first thoracic segment. ^ ,!. Both rami of swimming
feet tv/o-jointed. ^ ^ Feet of fifth pair rudimentary, with a single
linear segment bearing a long spine. Ova-sacs long, divergent.
Length 1 mm."

Very possibly the young of some species not now identifiable.
Only mentioned by Sars. (Compare C. diaphanus below.)

Sp. 24:. Cyclops serrulatus, Fischer.

(Plate 0. Figs. 17—19.)

? Cyclojis agiJis, koch (fide Rehberg).

Cyelopg serrulatus, lill.teborg, claus, sar3, lubbock, heller, fric, hoek, brady;

Cyclops longieornis, vernet.

Cyclops pecUnifer, cragix.

Although Rehberg positively asserts that Koch's name applies to
the present species, none of the numerous authors who have men-
tioned this most widely distributed form have employed any other
than the familiar designation, and the practical advantage to be
derived from its use seems to outweigh a quibble of doubtful
synonymy.

Cephalothorax oval, compact; abdomen slender and short, sud-
denly enlarged previous to its union with the thorax; antennae
slender, reaching nearly, but not quite to the last thoracic segment;
the last three joints are attenuated and furnish the most evident

character of the species; formula — :=r^ — ^^:r — -^ ; during

life the antenna3 tend to assume the form of a rude Z, the proximal
four joints forming the base; antennules small, reaching about to
the sixth joint of antenute; jaws small with large teeth; the single
segment of the fifth foot with three equal spines; egg-sacs oval, as
long as the abdomen; eggs few, dark; caudal stylets very long and
slender, spined along the outer margin; lateral setae small and ap-
proximated to the upper one; outer terminal seta short, spine-like,
in life set nearly at right angles to the others, spined or beaded

158 TAVELFTH ANNUAL KEPORT.

one margin and bristled on the other; the next seta is as long as
the abdomen, being somewhat exceeded by the following one; inner
seta as long as the outer, but feeble; upper seta nearly as long, ap-
proximated; length less than 1 mm.

A well marked variety of the above occurs in America, which
might rank as a species, were it not probable that it is simply a
post-imago form occurring only under favoring circumstances. This
variety has no connection with Brady's var. montanus.

Cyclops .serriilatns, var. eleg-aus. (Var. n.)

Distinguished from the type by the greater size, and the elonga-
tion of antennae and caudal stylets. We will first of all give the
measurements which afford a criterion for judging of the form and
proportions.

Total length 1.34 ram.; thorax 0.76 mm.; abdomen 0.40 mm.;
stylets 0.18 mm.; greatest width 0.42 mm.; inner median caudal
seta 0.60 mm.; outer median seta 0.36 mm.; inner seta 0.08 mm.
The first segment of the thorax is long proportionally (0.40 mm.)
The antennae are very long, reaching to the base of the third seg-
ment (.68 mm.). The egg-sacs are elongate-oval, being more slender
even than in typical C. serrulatus; in the animal measured they
were 0.50 mm. long, by 0.19 mm. wide. The caudal stylets are
slightly shorter than the last two segments of the abdomen. The
antennules are very short, and each joint has its series of fine teeth.
The free lower margins of the thorax are ornamented with series
of prominences, while the last segment is extended into a blunt
angle bearing long teeth. The last segment of the abdomen is
spiny-margined and is ornamented with a double row of spines at
the anus. The armature of the stylets as well as that of the feet is
identical with that in typical C. serrulatus. • The last two joints of
the antennae measure 0.1 mm. each, while the two previous measure
unitedly 0.12 mm. The color is not opaque as in the smaller form
usually. Brady's var. montanus has shorter stylets than the type,
but seems nearest the small dark form found in peaty waters in
America. Cyclops pectinifer, Cragin, has no distinctive points, it
being typical C. serrulatus.

Sp. 25. Cyclops macrurus, Sars,
Cyclops macrurus, brady.

Closely allied with C. serrulatus. Cephalothorax ovate, rounded

STATE GEOLOGIST. 159

anteriorly; last segment fringed at the angles with numerous fine
hairs. Antenna? much shorter than in C. serrulatus, about as long
as the first thoracic segment, otherwise similar. Abdomen attenu-
ated, penultimate segment margined posteriorly with spine-like
seise, the other segments pectinated. Caudal stylets very long and
slender, about equal in length to the three segments preceding,
bearing a group of four to five spines on the outside near the end,
otherwise unarmed. Length 1.3 mm.

Here is the natural place for C. spinulosus, of Claus, but there is
strong reason to suspect the validity of the species so very imper-
fectly characterized.

Sp. 26. Cyclops fluviatilis, Herrick.

(Plate Q^ Figs. 1—9.)
Cyclops magnoctavus, cragin.

This small species with twelve-jointed antenna? and conspicuous
coloration is widely distributed through the Mississippi valley. The
original description is appended.

''Body elongated; thorax very long; abdomen slender; stylets
about as long or longer than last abdominal segment; setse all very
short, not [always] pectinate; lateral and dorsal setae very small;
outer one spine-like, short and stout; two median set® short; inner
one very small and inconspicuous; antennae reaching nearly to the

base of abdomen [or beyond]; formula—^ — — :::: ; the

three joints following the six basal are much elongated, while the
terminal ones are but moderately so, a character which is peculiar
to this species; terminal segment slightly but evidently hinged and,
together vvith pair preceding, somewhat curved; feet with the ter-
minal spines strongly toothed; fifth foot very small, one-jointed,
bearing three small setae; operculum vulva? heart-shaped; egg-sacs
sub-quadrangular; eggs large; abdomen in the young much
elongated. Color deep indigo. Length 0.7 mm.'"

The first foot has upon the last joint of outer ramus three ex-
ternal spines, two apical setae and three internal setae; the outer
branch of fourth foot has three external spines, apically a spine and
seta and internally four setae.

Males of this species are slender, measuring about 0.75 mm.; the
abdomen being 0.28 mm., stylets 0.6 mm., first thoracic segment
•0.28 mm., and the longest caudal seta 0.24 mm. The antennae are
long and much modified so as to resemble superficially the antennae
of Diaptomus.

160 TWELFTH ANNUAL REPORT.

Auteniiai 11-joiuted.
Sp. 27. Cyclops cliaplianus, Fischer.

(Plate R. Fig. 12.)

7 Cyclops bkolor, Sars.

? Cyclops minutits, Glaus, Heller.

If not the young of other species, this is a widely distributed
form, being known from Russia, Norway, continental Europe,
Madeira, and America. The synonyms above given are upon the
authority of Re li berg.

The following description applies to our American form found
alwaj^s in connection with C. thomasi, C. pare us, or C. navus.

Very small, measuring 0.81 mm., setee not included. The thorax
is 0.5 mm., the abdomen .31 mm., the stylets .06 mm., the longest
caudal seta 0.4 mm., outer median seta .36 mm., the first thoracic
segment 0.3 mm., and the egg-sacs sometimes 0.4 mm. The thorax
is oval, the first segment being quite large, as in larval cj^clops.
The antennEe rarely reach the end of the first segment aud are
either 11-joiiited or obscurely 12-joiuted; their formula is
— ^— — — :=^ — --:r::r:. The first joint is very large.

The second antennae are of rather small size; the maxillipeds are
armed as in C. navus. The feet have usually but 2-joiuted rami,
but in large individuals some of the rami are obscurely 3-jointed.
The first foot has the terminal joint of the outer ramus armed with
three exterior spines, two terminal setffi and three interior setse^
the inner branch has one internal spine, a terminal spine and seta
and three external setae. The fourth foot has the terminal joint of
the outer ramus with two external spines, a terminal spine and seta
and four internal setas; the inner ramus has one internal spine^
two unequal spines and three internal setaa. There is also a series
of teeth at the place where the middle joint should appear. The
fifth foot consists of a broad, basal segment nearly fused with the
abdomen and bearing laterally a long spine; the terminal segment
is terete and small, having a single terminal spine. The caudal
stylets are but little longer than the last abdominal segment, which
bears teeth below; the sides are parallel, and the lateral seta is f
from base. The median setae are long and toward the end show
false jointing. The inner seta is longer than the outer which is,
however, heavier. Eggs eight to twenty, in narrow elongate sacs.
Not uncommon, everywhere.

STATE GEOLOGIST. 161

Sp. 28. Cyclops phaleratus, Koch.

(Plate R. Vigs. 6—10.)

(var. a.)

C. canthocarpoides, fischeb. coaus, lcbbock, fric.
C. phaleratus, KOCH, bars, uijanin, brady, kkhbkkg.
(var. b.)
C. afflni«, sarS.
Cpyofnieit^. rkhhero.
C. cuUjlescenti, heuricic.(-"C. perarmatus, cragiw.)

tC. kUtCiVUS, POGGKNPOL.

That the two varieties here united are very closely allied must
be admitted; that they are merely age forms is possible. Glaus in
figure 2 of his plate II (Freilebenden Copepoden) figures some
other species than the one described as C canthocarpoides, as can
be gathered from the elongated stylets and the eight-jointed an-
tennae. Our Minnesota specimens combine the eleven-jointed an-
tennae of C. affinis with the short stylets and peculiar form of the
fifth feet of the first mentioned. Rarely one is found with ten-
jointed antennae and at the same time sexually mature. The char-
acteristic oblique lines of spines at the base of the stylets may be
absent. Rehberg's figures of C. pygmaeus agree very well with our
species, but he has decided fhat it is not specifically distinct from
C. affinis.

It appears to me undesirable to institute a new species for the
American form, neither is it possible to sufficiently identify it with
any of the above.

I here append a brief description of Cyclops adolescens, Herrick
(=C. perarmatusj Cragin,) for comparison with the description of
C. affinis as transcribed below. Thorax oval, broad, acute anterior-
ly ; last segment large and separated by a constriction from the
anterior ones. The head is beaked below; first throacic segment
large and long (.36 mm.): last thoracic segment wide, united
closely with the first abdominal segment, armed with series of
teeth. Abdomen short, especially the last segment, which is
toothed behind ; stylets very short. The antennae are much
shorter than the first segment, eleven-jointed. The maxillipeds
are very small. All the feet ar3 armed with a row of very large
teeth or lanceolate spines down one side; fifth foot one-jointed, with
three spines, the outer being smooth, the others spiny; egg-sacs
variable, narrow, appressed; eggs large, color usually dark. The
animal moves like Canthocamptus, and is able to progress out of
water better than other species. The following measurements will
give an idea of the proportions: Length 1.26 mm.; thorax, 0,76
11

162 TWELFTH ANNUAL REPORT.

mm.; abdomen, 0.44: mm.; stylets, .06 ram.; longest seta, 0.34 mm.;
antenna?, 0.28 mm.; width of thorax, 0.44 mm.

Cyclops affinis, Sars.

" Antecedent! [C. phalerato] siniilllnius. Corpus autem minus robustum colore coe-
ruleo vel potlus glauco sat saturato insigne. Segmentuni ultimum tlioraeicum admar-
g iiem posteriorem extrosuni pilis vel spinulis subtllissimis peetenatim exornatum.
Rami caudales quam in C. phalerato aliqiianto longiores, setarum apicalium interna
quam externa multo breviore, intermediarum interiore altera fere trlplo longiore long-
itudinemque abdominis superante, in medio aculeata deln vero subtile ciliata. An-
tennae i -mi paris segmento l-mo corporis multo breviores, tenues. articulis U compo-
site. Pedes 5-ti paris distinct!, uniarticulati. satis 3, quarum interior ceteris multo
major et ciliata, Instruct!. Saccl oviferi parvi abdominl appressi. Longit. circit. X
mm."

Cyclops ornatus^ Poggenpol (=C clausii, Heller, fide Rehberg,) is
almost certainly, in our judgment, a young or atavic condition.

C. helleri, Brady, though not identical, is no more worthy a spe-
cific name. If every form with eleven-joiuted antennae and egg-
sacs be worthy a distinct name, it will be possible to duplicate all
the seventeen-jointed forms. Fortunately, however, many species
agree together in this condition, so that the number of spurious
species derived from this source is rather small ; among these is to
be reckoned C. nanus, Sars, which is obviously very near the pul-
chellus group.

Antenniip 10- jointed.

No valid species have permanently 10-jointed antennae. C. pha-
leratus is frequently found with 10-jointed antennae. C. kauf-
manni is without much doubt an immature form.

Antennae 8-.}ointed.

Sp. 29. Cyclops fimbriatiis, Fischer (fide Rehberg.)

(Plate R. Fi^. 11.)

C. crassicornU, sars, brady, hekrick.
C. gredleri, hkller.
C. pauper, fbic.

C. poppei, REHBERG.

(f C. magniceps, lil,l.teborg.)

Our American species corresponds to that described by Rehberg
as a new species. The differences mentioned in the previous report
(see Cyclopidae of Minnesota, p. 233) are just those which have
led Rehberg to establish the C. poppei, which, by the way, was

STATE GEOLOGIST. 163

found with the type. I see no reason, especially in view of the
latter fact, to regard it as even a well marked variety.

C. crassicornis is widely distributed in America as well as Europe,
but is never very common. The color is always reddish.

Antennae (3-jointed.
Sp .'{0. Cyclops ajquoreus, Fischer.

A brackish-water species, .85 mm. long, which in a number of
■characters departs from the type of the genus. Those who have
the opportunity to search the brackish pools along our coast would
do science a service by looking for this interesting species.

Note.— Cyclops navicularis, Say, is perhaps C. viildls of this report. C. setosus, Hal-
•deman, (TMiila. Acad. Scl.,Vol. VIII, p. 331) is referred iQ my notes toC. serrulatus, Ido
not now know with liow much reason.

The reader is referred also to Cyclops latisHmus, Poggenpol, as quoted by Cragin-
whicli, althdusjh belonging to the section having sevsnteen-jointed antennae, and hav-
ing feet like C. tenuicornis, Is said to have a disc-like body, long-jointed antennules
with no armature, and the basal j'>int of the abdomen very long.

Cyclopst ornatus is quoted by Cragin, but we are Itift in doubt as to the number of seg-
ments in the antennas, a point quite essential to th e definition of species.

(See under C. phaleratus.)

Cyclopi' longicauclatxvs and C. ignew are though! to be simply prematurely gravid
young of known species.

(See Cragin. 1. c.,(pp. 12— 13 )

Cycl/jps fischeri of the same author agrees with C. se^uoreus in having six-jointed an,
tennse, but in nothing else apparently. It is, if corr^actly described, a very remark-
able form, with uo seta on the antennae.

FAMILY HARPACTICIDtE.

Numerically the largest of the families of the Copepoda, this
group contains predominatingly marine and mostly minute animals,
frequently of strange and grotesque form. A few of the marine
forms, inhabiting the gulf of Mexico, are figured in the report of
the Minnesota Academy of Sciences for 1881. Of the over thirty
genera of the family less than a half dozen are not exclusively
marine, and of these most are brackish-water residents. The genus
Bradya contains blind copepods living in slime.

The name was proposed by Dana, but was dropped in the final
report. Again revived by Claus, it is now in use by the best
authors. The general form and structure closely resembles that of
the Cyclopidae. The following characters are the more important
ones in distinguishing the family from the other families of the
order:

164 TWELFTH ANNUAL REPOKT.

Body flattened or sub-cylindrical. Abdomen usually not much
Bmaller than the thorax, from which it is not separated by a sudden
constriction; antennae rather short, 4- to 10-jointed; mandibles
strongly toothed, palpate; maxillae well developed, palpate; first
pairofoiaxillipedes with strong teeth at the end, second pair usually
forming a claw. The first pair of feet are often turned forward or
prehensile; fifth pair one- or two-jointed, serving as egg supports
in the female.

Most species live among sub-aquatic vegetation.

The Sub-Family Canthocamptin.e,

to which our sole genus belongs, is further distinguished from the
other sub-families of Harpacticidas by the fact that the seconp
maxilliped has a prehensile hook. The feet of first pair are not
clawed, but have the inner branch elongated, and the palp of the
mandible is one-branched.

Genus Canthooamptus, Westwood.

These little animals may be secured in considerable numbers by-
gathering a supply of water from among weeds in shallow ponds,
and permitting the debris to settle in a spot where light only
touches the jar from one side, when the Cantliocampti congregate
on the exposed side.

Canthocamptus is an elongated animal, with the body divided
rather obscurely into two portions, of which the first, or anterior
portion, is largest. This part of the body has five segments, each
of which has at least one pair of appendages. The first, consisting
of the head proper with one of the somites of the body or thorax,
as is discovered by observing that a pair of legs is attached to it, is
the largest segment of the body.

As seen from above, it is triangular and extends in front into a
short, stout beak or snout, like the rostrum of a cray-fish. Above
the beak, in the center of the forehead, is the eye, consisting of
pigment and two lenses, showing that we really have to do with
two eyes confluent on the median line. This is the simplest form
of a compound eye. The same method of compounding the eyes
is exhibited in a more complicated manner by Daphnia and other
Cladocera. On either side of the beak springs an antenna with six
to nine joints of unequal size. The first three joints are profusely

STATE GEOLOGIST. 165

covered with hairs. The fourth joint is more slender than the
preceding, and terminates in a process below, which bears besides a
long hair a peculiar blunt bristle, that serves some unknown
purpose — probably being sensory in function like the similar hairs
on the antennae of some Cladocerae. The next joint is shorter than
the rest, while the remaining three are spined at definite points.
The antennae of the male are curiously altered, or geniculate, on
both sides, as in Cyclops. The three basal joints are shortened,
while more or fewer of the following ones are coalescent, followed
by a hinge joint and two elongated segments.

The second antennae or antenuules are two-jointed, and the basal
joint has a two-jointed branch or palp; the terminal joint is covered
with spines; at the end are longer and curved spines, jointed in the
middle.

The mandible is a flattened plate with digitate teeth at the end,
on one side of which springs a two-jointed palp, and from the other
a blunt process. The maxilla is somewhat like it, but has rudiments
of other elements.

The first pair of feet have two three-jointed rami. The outer
ramus is shorter and with the longer branch is directed forward.
The fourth foot has the inner branch two-jointed. The inner branch
of the third foot of the male is peculiarly modified to form a pre-
hensile organ, as it is this foot which fastens the spermatophore to
the female. The fifth feet are composed of two flat plates.

The second division of the body, the abdomen, consists of five
segments, of which, however, the first two are united in the female.
The last segment of the abdomen bears two stylets, which are some-
times considered as together constituting an additional segment.
Each of these stylets has, with several small spines, two elongated
caudal setae, one of which is usually as long or longer than the
•entire abdomen. The stylets are usually considerably longer than
wide, but the proportions vary somewhat in difi'erent species.

Viscera. The body cavity is traversed by the alimentary canal,
which is a straight tube with no lateral caeca or blind sacs, as in
■some other Copepoda. The canal is divided into four more or less
distinct portions; the first section is a slender, muscular tube, ex-
tending from the mandibles nearly through the first segment,
opening into the stomach proper, which is a muscular and gland-
ular sac or tube, filling the greater part of the thorax ; at the be-
ginning of the abdomen, the sac is constricted and becomes the ia-
testine proper ; near the extremity again there is another change
and the intestine loses its glandular character, and, by a peculiar

166 TWELFTH ANNUAL RIPORT.

adaptation becomes a sort of force-pump, which, durlug life, is con-
stantly pumping water in and out, serving as a means of respira-
tion. This anal respiration is quite common among aquatic ani-
mals in this as well as other orders. This latter section of the canal
is the rectum, and opens beneath a toothed anal plate, above and
between the stylets. No special divarications or caeca are append-
ed to the digestive traat, and the only other organ which is at all
considered to belong to the alimentary system, is what is known as
the "shell-gland," present in most Crustacea, but till recently
thought to be absent in Canthocamptus. It is a coiled tube found
in the lower part of the first segment of the thorax. It is impos-
sible to find this organ in Canthocamptus, in every case, it being
very obscure; and its oflice is uncertain, though it is supposed, per-
haps with little reason, to be hepatic in function.

There is no functional heart in this animal, but its place is taken
by a peculiar apparatus, hitherto undescribed ; this consists of a
tube, surrounding the posterior portion of the alimentary canal.
This sac around a sac is open in front, and serves by a double
mechanism the ofSce of a pulsating heart, though in a very imper-
fect manner.

There are no true haematic or lymph corpuscles in this animal ;.
so far, at least, none have been discovered. The place of these
blood corpuscles is taken by globules of yellowish or red color of
the most diverse size. These nutritive globules, or fat globules, as
they have been called, are undoubtedly reservoirs of nutriment in a
shape convenient for the animal's use, and equally certainly are
deiived from the contents of the intestine. In those Copepoda
which have a functional heart, it is open anteriorly into a general
body-cavity in the same way as in this animal. That a portion of
the vascular system should surround the alimentary canal, is no
unexampled thing, for in Daphnia a large sinus embraces a por-
tion of the canal. The same provision as this described in Cantho-
camptus occurs in the Cyclopidse. The nutritive globules are often
very large, and are frequently extremely abundant, especially in
females soon to become gravid. Three-hundredths mm. is not a
large measurement for the diameter of such drops.

The nervous system is very hard to trace, consisting of a large
pear-shaped ganglion just below the eye, from which extend
commissures around the oesophagus, connecting them with the
ventral ganglia lying between the bases of the feet. The senses
are not apparently well developed, for, excepting the eyes, we can-
not locate with certainty the organs of any sense. There are,

STATE GEOLOGIST. 167

however, two spots which are evidently devoted to special sense:
first, the processes on the fourth joint of the antenna?, which may
be simply the seats of tactile sense, or may have nerves suitable for
perceiving chemical stimuli; second, the area on the forehead bord-
ered by a raised line and covered with little pits, each with a small
bristle. The character of this organ can be but conjectured'; it may
be homologized with the frontal nervous organs of the Cladocera.

The sexual organs are quite extensively developed, and periodical-
ly obscure the remaining viscera. In the male the simple testis is
situated in the second segment, and the single vas deferens after
numerous windings through nearly the entire length of the body,
opens at the base of the first abdominal segment under a spined
plate. A part of the vas deferens is of a glandular character and
secretes an elongate tube., the sjjermatophore, which serves to con-
tain the spermatozoids, and is fastened by the male at the opening
of the median pore of the female; on contact with the water this
tube, which is at first soft, contracts and presses the contents into
the opening of the female organs. So long is the vas deferens that
as many as three spermatophores are sometimes seen in the body
at once. The spermatozoids are very small. The geniculated male
antennae are used in grasping the setae on the tail of the female,
and the curiously modified inner branch of the third foot of the
male may assist in fastening the spermatophore upon her body.
The ovary occupies the same position as the testes, and the two
ducts are coiled in the body from end to end, opening in the median
pore behind the fifth pair of feet. When the eggs are ready to be
laid, they are forced out, carrying with them a film of the secretion
of the lower, glandular portion of the ducts, which is of a collodion-
like consistency, and which forms the enclosing sac. The young be-
come fully developed sexually before they assume their final form,
and it is not unusual to find ova-bearing females which are not only
much smaller than the parent, but with considerable differences
in the various organs.

This sort of heterogenesis is not uncommon among lower Crusta-
cea, for the young may differ much from the mother till after they
have themselves produced young.

Four species have been recognized in America, of which one is
certainly identical with a widely distributed European form, and a
second is probably identical with an English species. C. palustris,
Brady, seems to depart considerably from the norm of the genus
and may prove a type of a marine genus. No true Canthocamptus
is more than accidentally marine.

168 TWELFTH ANNUAL REPORT.

The ten species below enumerated are all that have fallen under
the author's notice, though others may have been mentioned.

Ket TO THE Genus Canthocamptus,

„ f 2-jointed J ^ '"™' 1°"=! basal joint of 5th foot small C. grnfUi; Sara.

? I '0,5 mm. long: basal joint of 5th foot long. C. brevipes, Sara (,?).

. AntennaR thick C crasxus, Sars.

Inner ramus of

2-iointed"o^ I inner ramus ol I ^ntennre ^ C. trUpinosus, i Brady,

2-jomted . ,,j ^^^^ 2-jointed. [ slender. \ c. northumhricrc.. Hrady,

g. 3-jointed. -i

o" I ! Inner raiuus of j Stylets rather long. C minntus, Mueller.

& I I'M foot 3-joiiited. ' Styl. short, oval, C. ilUnoisensis, Forbes

o' . . J Male antenna normal C. hibernictui. Brady.

t» 1.3-Jomtea. -j ^j^jg antenna reduced, hooked at the end C. ? palnstris, Brady.

Canthocamptus elegantulus, C. mareoticus and C. horridus are
uncertain, probably referred to the wrong genus. C. stromii, Baird
( == Dactylopus stromii,) C. rostratus, Claus (= Stenhelia ima.)
C. virescens, C. linearis, and C. roseus of Dana, are marine Harpac-
ticidse of uncertain affinities. C. minutus of Claus is not sufficiently
described, but appears to be the earlier condition of C. minutus,
Mueller (C. staphynalis, Jurine).

Sp. 1. CaDtliocamptus gracilis, Sars,

Is elongated linear, with the abdominal segments smooth. Caudal
stylets long and slender; external caudal seta about one-fourth the
inner. All the feet with two-jointed inner rami; outer branch of
fourth foot longer than the others, inflexed; basal process of fifth
foot slightly expanded. Length 1 mm.

At Decatur, Alabama, was found a species of Canthocamptus
which is different from any American species, and seems in many
points nearest the above but, unfortunately, only a hasty sketch
could be made at the time, and the notes are insufficient to define
it. The form is not remarkably slender; the first and second ab-
dominal segments are very large. The caudal stylets are slender
and elongated, the inner seta being very long and curved, while
the outer is quite short. The anal plate is covered with hairs only.
The antennae are normal, of moderate length, and the fifth foot has
but a narrow process at the base.

1 Distinguished from the following by the presence of only three spines on the prooaes
of the basal joint of the fifth foot.

STATE GEOLOGIST. 169

If this form be worthy a distinctive name, it may he called

Sp. 2. Cantliocamptns tenuicaudis, (Sp. n.)
(Plate 0. Figs. 15 and 16.)

? Sp. 3 . Canthocaiiiptus brevipes, Sars.

This small form is almost certainly the young stage of some other
species; yet I transcribe the description.

"Corporis forma et magnitudine C. pygmseo non dissimilis. Segmenta abdominalia
vero postice magis attenuata seriebusque aculeorum destitiita. Rami caudales elongati
duplo longiores quam latiores, setis apicalibus brevisculis parumque divergentibus, ei-
teriore dimidiam longitudinem interioris non attlngente. Operculum anale absque
dentibus. Antennae 1-nii paris breves, articulis ultimls duobus in unum confluentibus
artlculum. Pedes natatorii brevissimi, ramo exteriore intus setis destitute, iuteriore
biarticulato in pedibus 1-mi paris longitudinem|exteriorissequante, in sequentibusmulto
breviore. Pedum 5-tl paris articulus basalis intus in proeessum foliiformem, sat mag-
num et angustatum, articulum ultimumelongato-ovatum aliquanto superantem, exit.
■Color albidus. Longit. parum supra '/imm."

Sp. 4. Cantliocaniptiis crassus, Sar3.

Robust; segments margined with pectinate bristles. Caudal
stylets oval, contorted, constricted at the base. Antennae thick,
densely covered with long setae. Fifth feet with long setae; basal
process rather small. All the feet excepting the first, with bi-
articulate inner rami. Length 0.75 mm.

Sp. 5. Canthooaniptus trispiuosus, Brady.

(Plate 0. Figs. 6—14.)

This species with the last and next has all the feet save the first
with bi-articulate inner rami. Very near the next, from which it
differs in the form of the fifth foot of the female, which has the
basal process smaller, bearing only three spines, while the next has
six, the second joint being longer and narrow. The male is un-
known. Not yet identified in America.

Sp. 6. Canthocamptus uortliuiubricus, Brady.

Body robust; antennae long as first segment, nine-jointed; man-
dibular palp minute. In the male the inner branch of the third foot
is three-jointed and dactylate, as in C. minutus.

170 TWELFTH ANNUAL REPORT.

Caiithocamptus nortluimbricus, var. americanus. (Var. n.)

(Plate 0: Figs. 6—14, 20—22.)

One of our mjpst common species is very near the English forra,
so near, in fact, that I dislike to remove it from it. A few points
of divergence, however, may be mentioned.

The form and proportions are much like those of C. minutus.
The head is large and ends in a prominent bent beak. The anten-
nae are rather long and slender and have a well marked llagellum.
(Brady figures no flagellum). The palp of the antennule is as in
C. minutus. The mandibular palp is small. The first pair of feet
normal, rather small; all the other swimming feet with two-jointed
inner rami, save in the case of the male third foot. The fifth feet
are exactly as figured by Brady, save that there is a prominence or
tooth of the basal segment near the point of attachment of the
terminal joint which is quite long. The sensory area of the head
is oval and pointed. The male antenna has a long flagellum, not,
as figured by Brady, a very short one. The egg-sac is very large,
oblong. The animal seems to fall short of the size of the English
species, though measuring upwards of 0.65 mm. Our form is very
well distinguished from any other species. It is found in lake
Minnetonka, lake Calhoun, and elsewhere.

Sp. 7. Cauthocamptiis minutus, Mueller.

Monoculus stapJiTjUnus, jurine.

L'anthocamptus minutus, lilljkborg, baird, sars, uljanin, brady, herricic.

Canthocamptus staphylinus, claus, frig.

Canthocamptus minutus, var. occidentalia, herrick.

A well known species which has been frequently described and
seems quite circumpolar in its distribution.

First mentioned from America in a paper by the writer in 1S78.
A pretty full description will also be found in the author's Types
of Animal Life. A very abundant species, frequent in muddy pools,
but somewhat variable in abundance. It may frequently be found
in great numbers in winter.

Sp. 8. Canthocamptus illinoisensis, Forbes.

( Plate 0. Figs. 1—5.)

This robust and pretty species was first taken near Minneapolis^
by Mr. A. W. Jones, a student of the University, who found it in
a peaty ditch. Forbes' description is appended.

"Length 1 mm. Head and first segment united; five abdominal

STATE GEOLOGIST. 171

segments in male, four in female. The suture between the first
and second segments is not wholly obliterated above in the female.

Last abdominal segment is deeply and acutely emarginate.
Branches oi furca as wide as long, inner bristle plumose, a little
longer than abdomen; outer plumose only on outer side, about half
the length of the inner. The second to fifth abdominal segments
have each a row of spinules along ventral portion of posterior,

Male with anterior antenme composed of seven joints, the fourth
joint very short. The front outer angle of the third is produced,
the blunt process bearing three long bristles surrounding a slender
olfactory club which is as long as the three following joints. The
penultimate joint bears a strong spine or slender appressed process
at the middle of its posterior margin. The five outer joints con-
stitute the grasping organ. The posterior antenme bear five long
bristles at tip, three of which are made prehensile by the occurrence
of from eight to twelve short articulations in the middle of the
hair, allowing it to be bent forward. At the base of these articula-
tions on the outer bristle, are two short spinules. Two nearly
longitudinal rows of five or six strong, short spines each appear on
the under surface of the outer joint of the antennule. The secon-
dary flagellum, borne as usual on the middle of the basal joint, is
not articulated, and bears four long bristles, two terminal and two
on distal half of inner side. The outline of the mandible is exactly
like that figured by Claus. but it bears about ten teeth, the upper
thick and blunt, the inner sharp, slender and longer. Several are
notched at tip. The lower angle bears a long simple bristle.
Mandibular palpus two-jointed, second joint with three long ter-
minal hairs and a shorter spine attached at basal third of anterior
margin, jointed at base and directed towards tip, like a dactyl.
The maxilla and maxillarg palpus are scarcely to be distinguished
from those of C. staphglinus.

The first maxillipeds are three-lobed, the outer lobe constituting
a long, strong claw. The second and third are about one-third as
long as the first, and bear each one strong simple spine and one
weak branched hair. The inner lobe is widest, about two-thirds as
wide as long. The dactyl of the posterior maxilliped is spinous on
its inner edge, and the same edge of the hand is ciliate and bears a
short, stout, sparingly plumose bristle at its base, just beyond the
tip of the closed dactyl. The width of this joint (the second) is
nearly half its length.

Basal joint of inner ramus oi first pair of legs nearly or quite as
long as outer ramus, the second wider but only half as long as the

172 TWELFTH ANNUAL REPORT.

third, aud obliqubly truncate. Inner ramus o{ third pair of legs in
male is three-jointed, [the outer two-jointed,]"" chelate. The finger
is o^ate, truncate, terminating in two long plumose hairs. The
dactyl is linear, curved at base, and twice as long as finger. The
inner ramus of the fourth pair of legs is about half as long as
outer, two-jointed, basal joint short, terminal joint about as long
as middle joint of outer ramus. The Jifth imir of legs is best de-
veloped in the female. In the male the length is not over one-
third the width. The basal portion bears three plumose hairs on
its very broadly rounded anterior margin, of which the innermost
is longest. The outer plate is nearly orbicular and bears five
spines on its terminal margin, of which the second from the inter-
nal angle is the longest. Genital plates^ found in male at posterior
border of first abdominal segment, beneath, are short, slightly ex-
panded internally, with internal angles rounded, and externally
bear three sub-equal bristles, jointed at base, the inner largest and
strongest and semi-plumose. The antennce of the female are eight-
jointed, extending backward to the first free segment. The basal
joint of the fifth pair of legs is sub-elliptical in outline, with the
basal half produced externally into a broad, triangular process
which bears the second joint on its posterior margin. The free end
of the basal joint bears six large plumose bristles of which the in-
ner is longest. The greatest width of the joint is nearly equal to
its greatest length. The second or outer joint is ovate, sub-trun-
cate, spined on each margin, and bears four plumose bristles at tip
and one at the middle of its outer margin. Its length is about
twice its breadth."

Sp. 9. Caiitliocamptus liibernicus, Brady.

A small species differing from all others save the next in having
a three-jointed inner ramus of the fourth foot.

"Anterior antennae of the female slender, 8-jointed, about as
lon§ as the first body segment, and mach like that of C. minutus.
Inner branch of the second antenna very small, 1-jointed. Poster-
ior foot-jaw having a broad hand armed with a long apical claw.
Inner branch of the first pair of feet scarcely twice as long as
the outer; first joint longer than the entire outer branch, and near-
ly twice as long as the united second and third joints, both of
which are extremely small. Inner branches of the second, third
and fourth pairs shorter than the outer, and 3-jointed, the first joint

* Evidently a misprint, for It Is the Inner ramus which is chelate.

STATE GEOLOGIST. 173

being very small. Inner segment of the basal joint of the fifth
pair of feet in the female elongated, fringed, bearing two long and
three short apical setae; second or outer joint sub-ovate, finely
fringed internally; externally bearing six long marginal setee. In
the male the limb is smaller, the basal joint short, broad and hav-
ing six short sette of equal length; second joint nearly like that
of the female. Caudal segments somewhat longer than broad; in-
ner seta about twice as long as the outer; anal operculum denticu-
late. Length .65 mm." Not found in America.

'to'

Sp. lO. Canthocamptus palustris, Brady.

(Plate K. Fig. 5.)

A brackish-water species about .9 mm. long, found in a number
of places in the British Isles. The species presents several anom-
alies.

The antennse of the female are 8-jointed; those of the male ro-
bust, the last joint forming a hook. The first four pairs of feet
have both branches 3-jointed; the fifth pair in the female are 2-
jointed, with a short and broad basal joint, the second joint being
sub-ovate, bearing five long apical set?e; in the male the fifth pair
13 obsolete, being reduced to a minute setiferous lobe. Caudal seg-
ments short, bearing two principal setae, the outer half as long as
the inner.

Sp. 11. Canthocamptus minnesotensis. (Sp. n.)

(Plate T. Figs. 1—6.)

Since the manuscript of this genus was finished, a small species
has been found which seems undoubtedly distinct from any of the
above. A single pair were taken in a gathering from Bassett's-
creek containing C. minutus in abundunce. Unfortunately the
characters of the swimming feet are not certainly known, but they
were apparently all three jointed save the last. The antennae are
very short and thick, 8-jointed, with a long flagellum; the anten-
nules are of the usual form, and the mouth parts rather large. The
first pair of feet have the two rami of nearly equal length. The
form is moderately elongate. The caudal stylets are very short,
quadrate in outline and well armed with spines. The fifth foot of
the female has four long and two short spines on the inner lamina,
and the terminal joint has five unequal spines. In the male the
fifth foot has two spines on the lamina and six on the second joint,.

174 TWELFTH ANNUAL REPORT.

one being a small bristle. The male antenna is of peculiar form.
The teeth of the anal plate are large and emarginate (see fig. 4.)
The swimming feet are all armed with very strong spines, aside
from the usual quota of spines at the end of each joint. Length
.65 mm.

Note.— C7. /ronfinalis, Rehberg. This author seems to liave parted with his usual
acumen in the remarl<s upon this species. After describing a Cauthocaniptus with the
inner ramus of the first foot "reiclilich doppeltso lang wie die beiden Grundglieder des
Aussennasts," he draws a moral on the mutability of genera from the fact that Brady
founded the genus Attheyella 'auf grund der Eingliede des innenastes am flerten
Fusspaare und einer derartigen Bildung des ersten Fusses, wie er bie C. frontinalis
beschreiben 1st." Brady says (Bi it. Copepoda, p. 58) : "inner branch of first pair of feet
scarcely at all elongated, and either 2- or 3-jointed," etc. The distinctive characters
being the 1- or 2-jointed 2d and 3d feet and the 1-Jointed inner ramus of the fourth foot,
it is doubtful if C. frontinalis is really new.

II. Genus Attheyella, Brady.

This genus, the diagnostic characters of which have been above
indicated, contains three norjiinal species. It is quite difficult to
say what differences exist between Sars' ''^Canthocamptus^'' pygmceus
and Attheyella spinosa. Brady did not seem to recognize the fact
that his diagnosis included that species. The third species is the
blind A. cyrptorum, of Brady, which it is interesting to compare
with the blind Bradya limicola of the coast of the gulf of Mexico.

PCECILOSTOMATA.

This group, consisting of animals more or less like Cyclops in
appearance, but, during part of their existence, semi-parasitic, has
been very little studied in America. Most of the fresh-water species
inhabit the gill-cavities of fishes. The gills of fishes should always
be examined (if practicable, microscopically) for these interesting
animals.

The mouth parts 9*e greatly reduced and their homologies un-
certain.

Genus Ergasilus, Nordmann.

Body shaped much as in Cyclops; anterior antennae short; anten-
nules in the female large, four-jointed, terminating in a strong
claw. Mouth opening in the center of the very large head, which
is not beaked in front. The mouth parts are inconspicuous, but
the maxilliped is a stout organ terminating in a long claw. The
three anterior pairs of feet are bi-ramose, and each ramus is three-

STATE GEOLOGIST.

175

jointed; the outer ramus of the fourth foot is two-joiuted; the fifth
pair is absent or rudimentary. The abdomen is four or five-jointed,
and the stylets are rather short. Ova-sacs two, large.

Ergasilus depressus, Sars.

(See Forhandlinger i Videnskabs-Selskabet, 1862.)

The form figured in plate S., fig. 1, is known from a gathering
taken under the same circumstances as Sars' specimens, and con-
sisted only of males. The animal is very transparent with deep
blue markings below, especially between the bases of the feet.
Sars thinks the males are always free, while the females early re-
tire to the gill-cavities of fishes. This species may be distinct from
the Norwegian form, but there is no reason for declaring that it is
so.

E. depressus is probably the young of the widel}' distributed E.
sieboldii.

Note. — As the systematic part of this work draws to a close, a
note is received from Prof. Birge, who was so kind as to glance
through advance sheets of the portion upon Cladocera, Prof. Birge
informs me that his Scapholeberis nasuta is the same as S. (Daph-
nia) aurita, Fischer, as published in 1849 in the Bull. Natur-
forsch. Gesellsch. in Moscaii, Bd. 22. This paper I have not seen.
At Prof. Birge's suggestion, then, read on page 43.

Sp. 4, Scapholeberis aurita, Fischer.

Daphnia aurita, fischkr.
Scapholeberis namita, birqe.

176 TWELFTH ANNUAL REPORT.

CHAPTER IV.

COLLECTING, PRESERVATION AND MISCELLANEOUS

NOTES.

The appliances employed in the capture and study of Entomo-
straca are, in the main, those employed by the student of aquatic
vegetation. The first in order of importance is the hand-net and
its accompaniment, long rubber boots, such as cover the entire
leg being preferable. Thus equipped, the student can collect by
far the greater numbe* of fresh- water Crustacea. The net is best
made by obtaining an ordinary gaff or dipping net of extra
strength but small size. If jointed, the ferrule must be unusually
strong, not, indeed, because of the weight or activity of the prizes,
but because it is often necessary to lift a net full of water, which is
a greater strain than the strongest fish would produce in a net
with open meshes. The ring of such a net is furnished with a me-
dium-sized bag of some porous but still rather close fabric. The
writer usually uses for this purpose the thinner variety of flour
sacking. This material fulls a little when wet, and permits the
water to pass rather too slowly, but this is a good fault. The net
is used in shallow water and among weeds. After the net has
been repeatedly filled and permitted to drain nearly empty, the
bottom of the net is seized and the small remaining amount of
water is thrown by a dexterous movement of the hand into a large-
mouthed jar, several of which are needed. By this method the ani-
mals can be secured in any desired degree of concentration, so to
speak, provided care is taken to avoid fouling the net with fine
mud or debris. A single jar should usually contain only a gather-
ing from a single locality. In case the collection is not to be ex-
amined at once, the gathering, which must now be quite free from
admixture of mud and filth, is concentrated as much as possible,

STATE GEOLOGIST. 177

and theu poured into a thin filter-paper or a thin muslin bag.
When nearly dry, the funnel is held over a small bottle, an open-
ing is made in the apex of the filter, and the contents washed
through with slightly dilute glycerine. Soon after pure glycerine
is added so as to bring up the whole to the required degre of con-
centration. A sufficiency must be used to well cover up the whole.
In case of haste the end of the filter containing the gathering may
be torn off and placed at once in a bottle of glycerine or alcohol.

For the collection of Cypridse it is recommended to use a very
thin fine net, and gather as much as possible of the finely commi-
nuted debris.which settles in weedy pools. Spread this material in
shallow pans and in an hour or so skim the surface with a small
spoon-like hand-net, and transfer with the addition of clear water
to shallow porcelain plates. Such gatherings may contain Ilyo-
cryptus, Monospilus, the hook-nosed Pleuroxids (=Pei'cantha) and,
perhaps, also species of Canti;ocamptus.

The entomostraca of the larger lakes must be sought by a differ-
ent method. A net of larger size, and composed of very thin ma-
terial is drawn after a boat which is kept moving in different parts
of the lake. Such a net should be so weighted as to receive water
from the surface as well as from several inches below it. The net
is emptied occasionally with plenty of water into large bottles,
which may preferably be placed in the dark if to be unexamined
for some time. Water kept in the dark will preserve its animal
life for a much longer time than if exposed to the sunlight.

A similar net may be placed in a rapid stream in such a way
chat it remains partly full, but does not overflow. The accumula-
tions of a day may be thus gathered into little space. The faucets
of the city water will frequently afford a good supply of animal
life, and unfortunately in Minneapolis a rather large number of
forms are worms of a suspicious and unpleasant appearance. It
must be observed that for this purpose the faucet must be well
open so that a good current is secured, otherwise most of the im-
purities will be dropped on the way. A friend mentioned that very
little life was found in the city water after long and careful experi-
ment, during which, however, a very small stream was allowed to
trickle through the complicated set of graduated screens. But the
writer at the same time secured a rather large supply both of en-
tomostraca and vegetable forms by simply permitting the water
from the hydrant faucet to flow with full head through a miisliu
net.

But our methods are not yet exhausted. The dipping bottle

12

178 TWELFTH ANNUAL REPORT.

frequentl}^ brings up animals quite different from those collected
by the towing net at the surface. This consists of a large bottle
weighted by a suitable bit of lead or iron and fitted with a tight-
fitting cork or wooden stopple. The stopple is attached to the line
fastened at the neck of the bottle iu such a way that a sudden
twitch of the cord opens the bottle when it has sunk to the re-
quired depth. Another method, when one does not object to ming-
ling forms from all depths, is to lower a net weighted with a heavy
ring to the bottom, there agitating it slightly and drawing it vertical-
ly upward. This serves in a poor way in the place of a dredge and
will secure a larger gathering than the dipping bottle, and is quite
as easily rigged. The collections secured in either of the above ways
are placed in large shallow porcelain plates and, the microscope be-
ing ready, the study may begin. With a rather large hand-mag-
nifier, with which, however, the student will soon be able to dis-
pense entirely, the various forms seen swimming or creeping or
springing about are scanned, chiefly for the purpose of noting
their motions. The little black, brown or yellow imps springing
on the surface are rapidly skimmed off as hindrances, and (if the
student is interested in the Podurte; consigned to a bottle of spirits.
Next a great Belostoma, Corixa, Water-skater, Ranatra, or Dysti-
cus requires the same treatment. Perhaps a half dozen '"whirligig-
beetle" require more time to dispose of, and then a careful remov-
al of the dragon-fly larvse and "water-tigers" leaves the coast com-
paratively clear save for sand-fleas and dipterous larv^ which must
be endured as necessary evils.

With a narrow slip of paper folded trough-wise the desired animal
is captured by a quick movement and the water permitted to drain
off, when the specimen is placed on the object-carrier, and a square
cover glass, one corner of which has been armed with a bit of wax,
is placed over the animal and then adjusted so as to give the re-
quisite amount of pressure to quiet its restless motions. The slip
of paper is, iu every way, more convenient than a dipping tube and
avoids flooding the object-carrier. With a half-inch objective and
suitable eye-piece the whole animal is drawn iu as natural a posi-
tion as possible, either with the aid of a camera or free hand, by the
assistance of careful measurements and a given scale. A one-fifth
inch objective is now substituted and all possible details added. If
any dissections are necessary, the cover glass may be removed, the
slide placed upon a slip of black paper and the parts separated as
far as possible by the aid of a watchmaker's glass or dissecting
microscope.

STATE GEOLOGIST. 179

Up to the present time almost the only reagent which could be
€raplo3'ed for the instantaneous killing of Entoniostraca with the
body in its natural position and the preservation of the same was
osraic acid, which partly on account of its expense, perhaps, seems
rarely to find its way into our laboratories. And even this is but
partially successful or causes such a dark color as to obscure what
one most desires to see. The desideratum seems to have been sup-
plied by the discovpry of Prof. Hermann Fol that ferric perchioride
produces not only an instantaneous death but a fixation of all the
parts with very little coloration or shrinkage. The alcoholic solu-
tion is diluted to about 2 per cent, and applied to a small quantitj^
of water in which the animal is swimming, or a more concentrate
solution is added at once to the water af a vessel containing numer-
ous Eutomostraca. The water is poured off and the animals washed
with alcohol of 70 per cent., to which a few drops of nitric acid
may be added to remove the ferric salts. According to Fol, in
transparent animals the appearance is very little changed b}- this
process. Specimens thus prepared may be preserved in alcohol
and afford preparations for making thin sections. They do not
take color well, but may be stained with gallic acid without diffi-
culty.

As a preservative, glycerine does admirably for Copepoda, tut no
known fluid works satisfactorily for the Cladocera unless after such
treatment as above indicated. Sections may be made by imbedding
in soap, but the tissues of the Cladocera are so delicate that the
writer never succeeded in making permanent preparations of such
sections. Either the alcohol or the balsam as it flows in almost in-
evitably disturbs the natural position. 50 grammes of soap are dis-
solved in 200 cu. cent, heated alcohol of 96 per cent. The soap
should be shaved very thin. A shallow paper trough is prepared
and filled with the still warm mixture, and the animal, which lies
in concentrated alcohol, is transferred into the solution and agitated
till its tissues are permeated with the soap. When cold, the bit of
soap is cut into the required form and is ready to be placed iu the
microtome.

As a preservative medium for Copepoda, Carpenters' gelatine an-
swers well. It consists of clarified gelatine, one ounce to six fluid
dramchs of pure glycerine. The preparations mounted in this re-
quire no cement, as the gelatine is quite firm when cold.

J 80 TWELFTH A]SNUAL REPORT.

APPENDIX.

The previous pages refer to the fresh-water crusj^acea simply and
will give a tolerable idea of the variety exhibited in the fauna of the
lakes and rivers of America. The majority of Copepoda are mariue
and the coasts of the United States will afford the student of
mariue entomostraca a rich harvest of curious forms. These ani-
mals are now being investigated, it is understood, by competent
naturalists. In the meanwhile any notes may be of a temporary
interest. The following jottings, which are the result of a few days
stay on Mississippi sound, will give an idea of the fauna of the gulf
of Mexico. They are extracted from a paper off"ered the Minnesota
Academy of Natural Sciences.

FAMILY CALANID^.

Genus Pseudo-diaptomus. (Gen. n.)

Resembling Metrida and Diaptomus; compactly framed; cepha-
lothorax 6-jointed, last two segments coalescent above; head round-
ed in front, beaked; eye small; antennae appearing 22-jointed in
both sexes, longer than the thorax; the right male antennas genic-
ulate as in Diaptomus; antennules bi-ramose, both rami rather short,
inner one seeming but two- or three-jointed; mandible ten-toothed;
maxillipedes well developed; feet all bi-ramose save the last, both
rami 3-jointed; first feet smaller; fifth feet with inner ramus obso-
lescent, in the male nearly as in Diaptomus, in the female rather
slender, simple, three-jointed; abdomen in the female 3-jointed, in
the male 5-jointed; stylets in the female longer; ova-sac single;
spermatophore pear-shaped.

This genus is of unusual interest on account of its close approach
to the fresh-water section of the family.

The spermatophore in this genus is large and swollen and, as

STATE GEOLOGIST. 181

seen through the hod.y of the male, is liable to be mistaken for
eggs.

Pseiulo-diaptomus pelagiciis. (Sp. n.)

Rgther compact; thorax alike iu the sexes, antennae short,
seeming 22-jointed; first foot small, both rami 3-jointecl; fifth feet
in the male with but small rudiments of the inner rami, basal
portion heavily armed with short teeth, otherwise almost as in
Diaptonms', fifth feet of female slender, alike; abdomen in male
very slender, with short stylets armed with five terminal seta3 and
a series of bristles on the inner margins, distal margin of segments
of abdomen toothed; a series of spines also ornaments the middle
of the first segment below; abdomen of female short and very
spiny, first joint thick, second slender, oblong, third joint short;
leugth of abdomen supplemented by that of the elongated stylets,
which are spiuulous on their edges; ova-sac ovoid, eggs numerous;
opening of operculum vulva3 with lateral projecting lips.

This species is ornamented with irregular markings of brownish
color which give it a strange appearance not observed in any other
copepod. The size is like Temora relax, which the female resem-
bles a little, a resemblance enhanced by the elongated stylets. By
some changes in the definitions of Metrida and Pleuromma these
three genera could be united, but there would then be no valid
excuse for not admitting Diapfomns^ so that, on the whole, it may
be well to let matters stand until we reach some better understand-
ing of the natural generic affioities of these animals.

Habitat, Mississippi sound, gulf of Mexico.

Genus Dias, Lilljeborg.

Slender ; cephalothorax verj' long, narrow in front ; abdomen
with five segments in the male, in the female with three; antennse
20-jointed, nodose ; secondary branch of antennules one-jointed,
small ; labrum lisrge; posterior maxillipeds short; swimming feet
with 2- and 3- jointed rami; fifth feet with a single ramus.

Dias long-ireinis, Lilljeborg ?

Unfortunately the gathering v/as insufficient to determine with
ci;rtainty the identity of our species with the above, but the female
agrees quite well; and those points in the youug males seen

182 TWELFTH ANNUAL REPORT.

which could be compared with the descriptions of D. longiremis
were sufficieutly concordant. This species ranges, iu the eastern
hemisphere, from the North sea to the Mediterranean, and could
be expected here. It is a very active animal and represents a well
differentiated type.

Genus Temora, Baird.

Elongate; thorax five-jointed, fourth and fifth segments closely
combined ; abdomen with four segments in the male, three in
female ; antennae 24- or 25-jointed ; right antenna of the male
geniculate; mouth parts as in Calanus; inner branches of second,
third and fourth pairs of feet two-jointed, of first one- or two-join ted;
fifth feet with but one branch, prehensile in the male.

Temora affinis, Poppe.
= r.. gracilis, hekrick, ms.

The shallow bays and estuaries along the Gulf of Mexico swarm
with a species of Temora but little unlike T, celox.

The body is much less compact, it being rather slender in both
sexes; in like manner the caudal stylets are very much elongate^
being nearly as long as in T. longicornis of Mueller, from which it
is clearly distinguished by many obvious characters, and which
seems to show an approach to Metrida.

The antenna? in male and female are just as in T. velox,, and the
fifth feet are little, if at all, dissimilar ; the spine on the second
joint in the female is not serrated, however, and the basal joint of
the abdomen in this sex has three teeth on either side. The caudal
stylets are about six times as long as broad in the female and
densely spined, as is the last abdominal segment. The stylets are
more slender in the male and have few spines, but the last abdom-
inal segment has three larger spines on either side. Inner ramus
of the first foot one-jointed. The animal is generally colorless, in
autumn at least, but may be variously ornamented with prismatic
colors, the most constant of which markings are a band about the
stylets and across the thorax and between the bases of the feet.
The ova are very numerous and carried as in Diaptomus. This
species is littoral in habitat and ranges from salt-water bays to the
fresh waters of rivers, along with several varieties of Cyclops^
Sida, etc.

STATE GEOLOGIST. 183

FAMILY HARPACTICID.E.

Genus Amyone, Glaus.

Body much compressed; dorsal margin strongly curved; head
very large, produced and angled below; antennae 6- to S-jointed;
antennules palpate, 3-jointed; second maxillipeds long, chelate at
the end; last thoracic and anterior abdominal segments enlarged;
filth feet leaf-like, large.

A very small crustacean, little over 4- mm. long, occurs in the
gulf of Mexico in shallow water among vegetation. Insufficient
material prevented its complete study, but it is nearly allied to A.
splicer ica, Glaus, from which it differs in several particulars.

I can do no better than quote the remarks of Glaus, the original
discoverer of this peculiar genus.

"The body of this highly remarkable form, represents, in its
general form, an intermediate stage between the nauplius (cyclops
larvae) and the mature copepods. The oval, almost spherical form,
the slight development of the abdomen and the enlargement of the
anterior thoracic segment recall the structure of the larva, while
the almost complete segmentation of the body, the jointing of the
antennae and the swimming feet, as well as development of the re-
productive organs, make the maturity of the creature certain. ""
(Beitr. zur Kenntniss der Entoni'^strakeu.)

Genus Laophonte, Philippi.

Rather slender; antenna 4-, 8-jointed; palp of antennules
1-joiuted; mandibular palp l-or-2-jointed; maxilla? palpate; first pair
'of feet slender, outer branch short, 3-jointed, inner branch elon-
gated. 2-jointed; three following pairs with one ramus 3-, the other
2-jointed.

Laophonte similis, Glaus?

The small crustacean which is referred to the above species oc-
curs sparingly in the brackish waters of Mobile bay, and with
Temora seems to be the only entomostracean not also found in the
fresh waters adjacent.

From the few specimens found it could not be certainly deter-
mined that our species is identical with the European. The dif-
ferences are, however, such as might be expected in immature speci-

184 TWELFTH ANNUAL EEPORT.

mens. Brady figures a similar reduction in the number of joints
of the antennae as that seen in oar specimens. The fifth foot too,
is less well armed with spines, but otherwise the agreement is tol-
erably close.

Genus Harpacticus, Milne-Edwards.

Elongate or expanded laterally; head united with the first thor-
acic segment; first and second abdominal segments coalescent:
antennge S-, 9-jointed; mandibular-palp 2-branched, large; second
pair of maxillipeds strongly developed; outer ramus of the first
pair of feet 2- or 3-jointed, inner ramus 2-jointed; first and second
joints of outer ramus elongated, second joint of inner ramus short;
both rami of following pairs of feet 3-jointed; ova-sac single.

Harpacticus clielifer, Mueller, (vai. n. ?)

The species inhabiting the gulf of Mexico resembles H. gracilis,
Claus, in the length of the setaj and some other peculiarities; but
the antennary palp is more liire H. clielifer^ with which it closely
agrees in most respects. Remembering that the eutomostraca
have their highest development in temperate and arctic regions, the
small size and greater proportional length of setse and stylets may
be explained. H. gracilis from the Mediterranean takes the place
of the true H. chelifer of the North sea, and is regarded by Brady
as the same species. Our form would, in. this case, stand more
nearly related to the typical form. Both branches of the first feet
are two-jointed and the antennary palp has three spines on its dis-
tal segment.

■'ti'

Genus Bradya, Boeck. (1872.)

Antennge very short, 6-, T-joiuted; antennules of moderate size
longer than antennas, with a 2- or 3-jointed palp; mandibular palp
large; maxillipeds rather large, outer branch (first foot-jaw of
Brady?) much as in Calaniche; first four pairs of feet nearly alike;
fifth pair small, not lamellate.

This peculiar genus is not yet well circumscribed and defined,
and it is much to be regretted that lack of time prevented from
ascertaining how far the western species agrees with the generic
characters of the European form and thus determining the validity
of the assumed generic criteria. That our species is a member of
the genus can not be doubted, but the hurried examination which
could be devoted to it failed to cover the entire structure.

STATE GEOLOGIST. 185

Braclya liiuicola. (Sp. n.)

Body flattened ; free margins of the segments of the dorsal cara-
pace rather long; little separation between abdomen and thorax;
abdomen cj'lindrical, rather long; stylets short; distal margin of
the segments spined ; antennas ver}^ short, 6- or 7-jointed, hardly
longer than the movable beak ; second antennae much longer,
3-jointed; palp long, two-jointed-; mandibles palpate, teeth fine,
m.uch as in Calanid^; palp bi-ramose, second ramus very small ;
maxillffi of moderate size; maxillipeds large, outer one as in Cala-
nidse; first four pairs of feet bi-ramose, each ramus 3-jointed ; fifth
foot small, with two terminal digitate processes and a seta on either
side. The male is at least a third smaller and has longer caudal
stylets; the antennas are modified, but very short. The eyes are
wanting in both sexes. This very interesting species was collected
in the brackish water of a ditch shaded by high sedges so that the
sun could hardly panetrate. I did not find any representative
of the genus in the open waters neighboring, but it is hardly to be
doubted that such exist. This species is quite distinct from Bm-
di/a tijpica of north Europe.

The only other blind copepod with which I am familiar is
Att/iei/eUa, which is circumstanced somewhat as the above.

The European B. fi/pica is pelagic; ours dwells in darkened
ditches and seems to furnish another illustration of the effects of
seclusion upon the visual organs. Brady seems to have transposed
the maxillipeds; these are really but branches of the same organ,
as shown by the development, and the outer ramus is, probably,
what Brady usually calls second foot-jaw but here first foot-jaw.
In the characters of the mouth parts and fifth feet our species
seems to show an affinity with the elongated higher copepoda.

Ocean Springs, Mississippi.

Calig-us americaims, Dana and Pickering ?

A species of Caligus was collected at dusk far out in Mississippi
sound in considerable numbers. The anmials were floating in a
bank of vegetation and swam freely. They seem not to differ
greatly from the species described by Dana and Pickering in 1838
from the cod near New York. The fish lice are remarkable for
their flattened bodies and the paired sucking organs on the head.

A species of Corycceas allied to C. varit(s uf Dana was also col-
lected.

186

Note. — Prof. Forbes, to whom advance sheets of the portion ou
Copepoda were sent, writes me that he somewhat questions the
identity of the Minnesota species of Diaptomus referred to D.
leptopus with the species for which that name was proposed. I do
not know of any facts casting doubt upon the reference, but wish
to call the reader's attention to the suggestion of Prof. Forbes.

INDEX

Page. Page.

Acanthocercus rigidus 73 A. tenuicaudis 95

Acanthocercus sordidus 76 A. testudiuaria 90

Acantholeberis, Genus 73 Alonella, Section 101

A. curvirostris 78 A. excisa 103

A. dentata 73 A. exigua 105

Acroperus, Sub-genus 81 A. grisea 105

A. angulatus 82 A. pulchella 103

A. cavirostris 82 A. pygmsea 105

A. harpje 81 A rostrata 102

A. iutermedius 85 A. striata 106

Alona, Sub-genus. 92 Alonopsis, Genus 85

Alona, Section 92 A. elongata 85

Alona, Key to section 93 A. latissima 86

A. affinis 98 A. media 86

A. angulata 95 Amyone, Genus 183

A. camptocercoides 95 A. sphterica 183

A. costata 97 Anchistropus, Genus 118

A. dentata 99 A. emarginatus 118

A. elegans 99 Appendix 180

A. elongata 85 Attlieyella, Genus 1 74

A. esocirostris. . 90 A. cryptorura 174

A. glacialis 100 A. pygmtea 174

A. glacialis, var. tuberculata 101 A. spinosa 174

A. glacialis, var. Icevis 101 Bosminidse, Family 65

A. guttata 94 Bosmina, Genus 65

A. intermedia 101 B. brevirostris 65

A. lineata 96 B. cormita 65

A. modesta 97 B. curvirostris 65

A. oblonga 97 B. diaphana 66

A. parvula 99 B. lacustris 66

A, parvula, var. tuberculata 100 B. lilljeborgii 65

A. porrecta 99 B. longirostris 65

A. quadrangularis 97 B. longispina 6o

A. rectangularis 96 B. macrorhyncha 65

A. reticulata 90 B. maritima 65

A. sanguinea 95 B. microps 65

A. sulcata 97 B. nitida 65

188 IND

B. obtusirostris 66

B. striata 66

Bradya, Genus 184

Bythotrephes 122

Calaniclte, Family 129

Caligus 18

Calyptomera, Sub-order 15, 18

Camptocercus, Genus 81

C. biserratus 83

C. latiiostris 84

C. lilljeborgii 84

C macrurus 83

C. rectirostris 84

C. rotundus 84

Canthocamptus, Genus 164

C. brevipes 169

C. crassus 169

C. frontiualis 174

C. gracilis 168

C. hibernicus 172

C. illinoisensis 170

C. minnesotensis 173

C. minutus 170

C. northumbricus 169

C. palustris 173

C. staphylinus 172

C. tenuicaudis and trispinosus . . 169

C. pygmiieus 174

Carpenter's gelatine 179

Ceriodaphnia, Genus 35

C. alabamensis 38

C. consors 40

C. cristata 37

C.dentata 38

C. laticaudata 39

C. megops 36

C. nitida 41

C. pulchella 37

C- punctata 39

C. quadrangula 40

C. reticulata 38

C. rotunda 37

C. scitula 40

C. textilis 41

Chydorus, Genus 115

C. albicans 118

C. cffilatus 117

EX.

Page.
C. globosus 116

C. latifrons 118

C. latus 117

C. nitidus .117

C. ovalis 117

C. piger 118

C. sph?ericus 116

Circulatory system of Daphni-

dre 23

Circulatory system of Cantho-
camptus 166

Cladocera, Order 13

Copepoda, Order 124

Corethra, A new species of 10

C. appendiculata 11

C. plumicornis 10

Corj'C8eus, Genus 185

Ctenopoda, Tribe 18

Crustacea, Distribution of fresh-
water 1, 6, 7

Cucullanus elegans 9

Cyclopidse, Family 143

Cyclops, Genus 144

C. abyssorum 149

C. adolescens 161

C. sequoreus " 163

C. afflnis 161

C. agilis 157

C. albidus 153

C. annulicornis 153

C. ater i45

C. bicolor 160

C. bicuspidatus 151

C. bisetosus 151

C. brevicaudatus 147

C. brevicornis 145

C. brevispinosus 148

C. canthocarpoides 161

C. capillatus 156

C. clausii 153

C. coronatus 153

C. crassicaudis 156

C. crassus 1 46

C. crassicornis 162

C. diaphanus 157, 160

C. elegans 158

C. elongatus 144

i^PEx. 189

C. fimbriatus 162 C. simplex 150

C. fischeri 163 C. spinulosus 159

C. fluviatilis 159 C. streuuus 147

C. f urcifer 147 C. teuuissimus 150

C. gigas 145 C. tenuicornis 153

C. helgolandicus 155 C. thomasi 151

C. helleri 162 C. uniaugulatus 149

C. hj-alinus 150 C. varicans 157

C. ignens 163 C. vernalis 147

C. ingens 145 C. viridis 145

C. insectus 151, 152 C. vulgaris 145

C. insignis . .' 155 Daphnella, Genus 21

C. lascivus 161 D. brachyiua 21

C. lacustris 146 D. braudtiana 22

C. languidus 154 D. expinosa 21

C. latissimus 163 D. wincbelli 21

C. leuckartii 146 D, wiugii 21

C. leemvenhoekii 150 Daphnidse, Family 23

C. longicaudatus 163 Daphnia, Genus 49

C. longicornis 157 D. apicata 63

C. lubbockii 155 D. aurita 175

C. lucidulus 147 D. berolinensis 63

C. macrurus 158 D. carinata 58

C. magniceps 162 D. cavifrons 58

C. magnoctavus 159 D. cederstromii 64

C. minutus 160 D. cristata 63

C. modestus 154 D, cucullata 63

C. navus 152 D. dubia 61

C. nanus 162 D. galeata 60

C. uavicularis 163 D. bastata 57

C. obesicornis 153 D. hj^alina 60

C. oithonoides 150 D. kalbergensis 63

C. ornatus 162 D. lacustris 59

C. parens 148 D. Isevis 60

C. pauper 162 D. lougiremis 63

C. pectinifer 157 D. longispina 58

C. phaleratus 161 D. magna 55

C. pictus 147 D. magniceps 64

C. poppei 162 D. miunehaha 57

C. pulcbellus 155 D. obtusa 57

C. pygmceus 161 D. ovata 56

C. quadricornis, var 153 D. pennata 56

C. robustus 147 D. pellucida 60

C. scutifer 149 D. psittacea 55

C. serrulatus 157 D. pulex 57

C. signatus 153 D. pulex, var. nasuta 57

C. signatus, var. faciacornis .... 153 D. retrocurva 64

190

INDEX.

Page.

D. rosea 59

D. schffifferi 55

D. schoedleri 57

D. similis 59

D. vitrea 64

Daphnia, Development of 50

Diaphanosoma brandtianum 21

Dias, Genus 181

D. longiremis 181

Distomum 9

Drepanothrix, Genus 73

D. dentata 73

D. hamata 73

D. setigera 73

Diaptomus, Genus 135

D. armatus 139

D. castor 137

D. kentuckyensis 142

D. gracilis 141

D. giganteus 139

D. laticeps 141

D. leptopus 140

D. longicornis 140

D. minnetonka 138

D. pallidus 142

D. sanguineus 138

D. sicilis 142

D. similis 141

D. stagnalis 139

D. westwoodii 137

Enemies of Entomostraca 8

Epischura, Genus 130

E. fluviatilis 132

E. lacustris 131

Ergasilus, Genus 174

E. depressus 1 74

E. sieboldii 174

Eurycercinse, Sub-family 80

Eurycercus, Genus 80

E. lamellatus 80

E. laticaudatus 80

Evadne 122

Ferric perchloride 179

Graptoleberis, Genus 89

G. inermis 90

G. reticulata 90

G. testudinaria 90

Pafte.
Gymnomera, Sub-order 120

Ilarpacticidre 183

Harpacticus, Genus 184

n. chelifer 184

H. gracilis 184

Harporhynchus falcatus 114

Heterocope, Genus 130

H.alpina 130

H. appendiculata 130

H. saliens 130

HolopedidjB, Family 22

Holopedium, Genus 22

H. gibberum 22

Ilyocryptus, Genus 76

I. acutifrons 77

I. sordidus 76

I. spinif er 77

Introductory 5

Lagenella mobilis 12

Laophonte 183

Lathonura, Genus 71

L. rectirostris 71

L. spinosa 71

Latona, Genus 22

L. setifera 22

LeptodoridoB, Family , . 122

Leptodora, Genus 123

Leydigia, Genus 88

L. acanthocercoides 89

L. quadrangularis 88

Limnocalanus, Genus 142

L. macrurus 143

Limnosida, Genus 21

L. frontosa 21

Lophophorus 143

Lyuceidaj, Family 77

LynceiTia3, Sub- family 81

Lynceus, Genus. (See Alona and

Pleuroxus).

Lynceus acanthocercoides 89

L. affinis 98

L. excisus 103

L. exiguus 105

L. lamellatus SO

L. laticoruis 68

L. leucocepbalus 81

L. lineatus 96

IXDEX.

191

Pape.

L. macrurus 83

L. nanus lOo

L. quadrangularis 88

L. reticularis 90

L. rostratus 102

L. splijericus 116

L. tenuirostris .119

L. testudinarius 90

L. trigonellus 108

L. truncatus 112

Lyncodaphnida?, Family 66

Lyncodaphnia, Genus 74

L. macrothroides 75

Macrotlirix, Genus 68

M. laticornis 68

M. pauper 70

M. rosea 69

M. tenuicornis 70

Metrida 182

Misophria 143

Monoculus ( = early synonym for
Lynceus, etc.)

Monospilus, Genus 119

M. dispar 119

oSTote to Cladocera 1 75

Note to Copepoda 186

Oithona 143

Osphranticum, Genus 134

O' labronectum ■ 134

Pasithea 71

Percantha truncata 112

Plirixura, Genus 114

P. rectirostris 115

Pleuroxus, Sub-genus 106

P. acutirostris 109

P. adunctus 109

P. affinis Ill

P. bairdii 109

P. denticulatus 110

P. glaber 113

P. hamatus 110

P. nasutus 114

P. personatus 113

P. procurvus 113

P. trigonellus 108

P. truncatus 112

P. uncinatus 114

Paee.
P. unidens Ill

Podon, Genus 122

Poecilostomata, Order 174

Pontellidte 129

Polyphemidpe, Family 120

Polyphemus, Genus 121

Potamoicbetor 134

Pseudo-cjclops 143

Pseudo-diaptomus, Genus 180

P. pelagicus 1 80

Pseudo-sida, Genus 20

P. bidentata 20

Eypophilus ' 107, 113

Scalicerus pediculus 121

Scapholeberis, Genus 41

S. angulata 44

S. armata 43

S. aurita 1 75

S. cornuta 43

S. mucronata 42

S. nasuta 43

Scopliipbora vagans 1 80

Sectioning entomostraca 179

Sida, Genus 19

S. crystallina 20

S. elongata 20

Sidida3, Family 19

Simocephalus, Genus 44

S. americanus 47, 48

S. congener 48

S. daphnoides 48

S. expinosus 47

S. rostratus 47

S. serrulatus 46

S. vetulus 46

Streblocercus, Genus 72

S. minutus 72

Tachidius 129

Temora, Genus 133, 182

T. affinis .....133, 182

T. armata 133

T. finmarchia 133

T. gracilis 133, 182

T. longicornis 133

T. velox 133, 182

Thorellia 143

Utricularia vulgaris 8

PLATES OF PART V.

13

PLATE A.

Fig. 1. abdomen of Moina paradoxa,, female, from Minnesota.

Fig. la. spine from post-abdomen.

Fig. 2. post-abdomen of Moina rectirostris.

Fig. 3. head of M. paradoxa^ female, showing (a) eye with pig-
ment and lenses, (b) supra-oesophagal ganglion, anten-
nule with (c) its muscle, (d) its nerve, and (e) its terminal
sensory filaments, (f) the cascum of stomach, (g) optic
ganglion, (h) stomach, (i) oesophagus, (j) the muscles
which move the eye, also part of the labrum.

Fig. 4. antennae of same.

Fig. 5. ephippium of M. rectirostris.

Fig. 6. " of M. paradoxa.

Fig, 7. seminal cell of M. paradoxa ; 7a, a group less magnified.

Fig. 8. seminal cells of M. rectitvstris.

Fig. 9. first foot of male of M. paradoxa.

Fig. 10. " " " " '■ ;i^, rectirostris (from Weismann),

Fig. 11. male M. rectirostris (from Weismann).

Fig. 12. head of Ceriodaphnia rotunda. ( This and the following
numbers after P. E. Mueller.)

Fig, 13. head of C. pimctata.

Fig. li. " C. pulchella.

Fig. 15. " C. reticulata.

Fig, 16. " C. quadraufjula.

Fig. 17. " C. quadrangida.

Fig, 18. post-abdomen of C. quadrangida.

Fig. 19. '' C. pulchella.

Fig. 20. " C. megops.

Fig. 21. " C. reticulata.

Fig. 22. " C. laticaudata.

Fig. 23. " C. rotunda.

MINNESOTA CRUSTACEA

12tK Annual Report PLATE A.

GeoL & Nat. HistSur. Minn.

PLATE B.

Fig.

1.

Fig.

2.

Fig.

3.

Fig.

4.

Fig.

5.

Fig.

6.

Fig.

7.

Fig.

8.

Fig.

9.

Fig.

10.

Fig.

11.

Fig.

12.

Fig.

13.

Fig.

14.

Fig.

15.

Ceriodaphnia rotunda, male (after Kurz).

C. cdahameHsis. female.

C. retkidata, post-abdomen of male with opening of vas

deferens (after Weismann).

C. consors ? ?

C. scitula, head of female.

do., post-abdomen.

do., antennule of male.

do., semen cell of male.

Scapholeberis angulala, adult female; 9a. first foot.

Schapholeberis armata^ "

do., view from below.

Lijrxodaphnia macrotJiroides, youag.

do., labrum.

do., antennule.

do., last foot, purple pigment in lower part.

MINNESOTA CRUSTACEA.

m tfi Annual Report

PLATE B.

Geol & 2^at Hist. Sur Alinn.

PLATE B'.

Fig. 1. LijncodapJinia macrothroides (= Ofnjoxus?), adult female,
showing coiled intestine, elevated anus, long antennules,
elongated seta of second antennae, anterior caeca, etc.

Fig. 2. post-abdomen of the same.

Fig. 3. antennule.

Figs. 4—6. Polyphemus pediculus, young and adult females.

MINNESOTA CRUSTACEA.

From the 10th Annual Report. PLATE B i . Geol. & Nat. Hist. Sur. Minn. *

PLATE C.

Fig. 1. Macrothri.r teniiicornis, la. labrum.

Fig. 2. do., first foot.

Fig. 3. do., antenuye of young.

Fig. 4. Macrothrix pauper.

Fig, 5. il/rtc>'o/Ari> rosm, antenna of male.

Fig. 6. do., spines of shell-margins.

Fig. 7. do., post-abdomen.

Fig, 8. Macrothrix laticornis, male.

Fig. 9. do., semen cells.

Fig. 10, Pasithea rectirostris, male antenna.

Fig. 11. Macrothrix rosea, post-abdomen.

Fig, 12, Macrothrix fenuicornis, "

Fig, 13. Macrothrix rosea, post-abdomen of male.

Fig, 14. Drepanothrix clentata, antenna.

Fig. 15, Ihjocrijptus sordidus, marginal spines.

Fig, 16. do,, antenna.

Fig, IT. do,, post-abdomen.

Fig. 18. Ilyocrijptiis spinifer, 18a. marginal spines.

Fig. 19. do., antenna.

Fig. 20. Macrothrix fenuicornis, heart and accompanying vessels

Fig. 21. Ihjocrijptns spinifer, post-abdomen.

MINNESOTA CRUSTACEA.

i'' ^Annual Report

PLATE C.

Geol & Nat Hist. Sur. Minn..

;g\CAr

PLATE D.

Fig. 1. Lathonura rectirostris.

female, from above, a. eye. b. optic ganglion, c. mus-
cles of eye. d. muscles of antenna, e. dorsal sucking
disc, f stomach, g. young in brood cavity.

Fig. 2. female, from side.

Fig. 3. head seen from below.

Fig. i. maxillee.

Fig. 5. first foot.

Fig. 6. ovary.

Fig. 7. antennule.

Fig. 8. last foot.

MINNESOTA CRUSTACEA.

ISth^nnuaZ Report

PLATE n.

Geol &NcU.Hist. Sur. Minn.

PLATE E.

Fig. 1. Alona quadrangular is, female.

A. anteunule. Lb. labrum. Md. mandible. P-a. post-
abdomeu. Au. anus. F, c. musculus flexor caudalis.
E. c. musculus extensor caudalis. A. g. anal gland,
n. g. nutritive globule in embryo, t. tail of embryo.
I, II, III, IV, V. five pairs of feet of embryo, mx. maxilla
of embryo, at^. antennae of embryo, at^ antennules
of embryo. H. heart. Sh. g. shell gland. Ov. ovary.
Md. m. muscle of mandible. At.^m. muscle of antennae.
E. eye, s. ce. g. supra-cesophagal ganglion. P. F. pig-
ment fleck.

brain, eye and pigment fleck of same.
Pleuroxus procurvus, female,
foot of same.
Acroperus leucocephalus.
Alonella excisa, female; 6a. shell of same,
antennae of same.
Alonopsis latissima, female.
Alonopsis media, female.
Camptocercus macrurus, post-abdomen,
lower angle of shell of same.

Fig.

2.

Fig.

3.

Fig.

4.

Fig.

5.

Fig.

6.

Fig.

7.

Fig.

8.

Fig.

9.

Fig.

10.

Fig.

10a,

MINNESOTA CRUSTACEA.

12 1/^ Annual Report

PLATE E.

GeoL & IfiU. Hist. Sur. Min n.

-'"' LJLJ""' ' ' , t q/

y#r^^c«.

PLATE F.

Fig. ]. Chijdorus globosus.

Fig. 2. do., first foot.

Fig. 3. do., eud of post-abdomen.

Fig. 4. Chydorns spliicricus^ mdXc.

Fig. 5. Chydonis nitidus, post-abdomen of female.

Fig. 6. Chydorus nitidus, head.

Fig. 7. Chydorus spluericus^ ephippial female.

Fig. 8. do., female.

Fig. 9. Chydorus globosus, post-abdomen of male.

Fig. JO. Chydorus sphxrricus^ from above.

Fig. 11. Chydorus oralis.

Fig. 12. Chydorus ccdatus.

Fig. 13. Crepidocercus setiger.

Fig. 14. Alona offinis.

Fig. 15. Pleuroxus unidens; 15a. antenna.

MINNESOTA CRUSTACEA.

1^ tfi Annual /it^porf

PLATE F.

Geo I & 2^at Hist Siir Minn..

PLATE G.

Fig. 1. Alonopsis latissima^ male.

Fig. 2. Alona glacialis ? female.

Fig. :^. do., male.

Fig. 4. Alona tuhercnlata.

Fig. 5. do., post-abdomen.

Fig. 6. do., labrum.

Fig. 7. do , antenna, setose branch.

Fig. 8. Alona glacialis, antenna.

Fig. 9. Alonopsis latissinia, feot.

Figs.lO, 11. Alonella excisa, details of shell sculpture.

Fig. 12. PleuroxHS denticiUatiis, female; 10a. outline of ephippiura.

Fig. 13. do., common variety.

Fiar. 14. Alona tuberculata. var.

MINNESOTA CRUSTACEA.

J~ t^ Annital Rpport ^

PLATE G.

Ceol. & tTat Hist Sur Minn.

PLATE H.

Fig. 1. Pleuroxus Jmrnatus, post-abdomen and antenna.

Fig. 2. Pleuroxus affinis.

Fiff. 3. Alona modestu {= lineata?)

Fig. 4. Leydigia quadrangularis.

Fig. 5. Euri/cercus lamellatus, male; 6&. i^osterior margin.

Fig. 6, do, antenna of female.

Fig. 7. Ahnella pygmwa.

Fig. 8. Temora qfinis, Foppe. female.

Jfig, 9. do., abdomen of female.

Fig. 10. do,, male.

Fig. 1 1. do., abdomen of male.

Fig. 12. do,, fifth feet of male.

Fig. 13. do., '' " of female.

Fig. U. do., jaw.

Fig. 15. do., antennule.

Fig. 16. ' Nauplius larva of this or a related species.

MINNESOTA CRUSTACEA

^'^\><Annijninrport PLATE H.

GeoL & 2fai. Hist. Sur. Minn.

I

PLATE I.

Camptocercus rectirostris^ post-abdomen of female.

do. post-abdomeu of male.

do. male.

Camptocercus biserratus, head.

Camptocercus latirostris, head of male.

do., head of female,

Camptocercus lilUjehorgii^ head.

do., post-abdomeu of female.

Acroperus leucocephalus, post-abdomen of male.

Acroperus angustatus, '^ ''

Alona temiicaudis, post-abdomen.

Alona dentata, post-abdomen.

do. female.

Alona elegans.

Alona intermedia.

Pleuroxus hastatns.

Leptorhynch us falcatus.

Phrixura rectirostris.

Eurycercus lamellatus, first foot of female,

Alona sanguinea? shell markings.

Monospilus dispar; 21a. do., head seen from in front.

Figures 19-21 original, others from Kurz, P. E. Mueller and Schoedler.

Fig.

1.

Fig.

2.

Fig.

3.

Fig.

4.

Fig.

5.

Fig.

6.

Fig.

7,

Fig.

8.

Fig.

9.

Fig.

10.

Fig.

11.

Fig.

12.

Fi-.

13,

Fig.

14.

Fig.

15.

Fig.

16.

Fig.

IT,

Fig.

18.

Fig.

19.

Fig.

20.

Fig.

21.

MINNESOTA CRUSTACEA.

12th Annual Rt^porl J^LATE I. Geol & Xat Hist Sur Minn.

4

PLATE J.

Ceriodaphnia scitula^ (small var.) ephippial female.
Bosmina longirostris.

Bosmina lilljehorgii. After P. E. Mueller.
Bosmina^ hook on the first foot of male.
Scapholeberis m ucronata .
Scapholeberis cormita, head.
Scapholeheris angulafa, head; 7a. angle of shell.
Pleuroxus denticulatiis, male.
Simocephalus americamis, head of female.
Fig. 10. Bosmina, post-abdomen of male (after Weismann).

Fig.

1.

Fig.

2.

Fig.

3.

Fig.

4.

Fig.

5.

Fig.

6.

Fig.

7.

Fig,

8.

Fig.

9.

MINNESOTA CRUBTACeA-

1" */<■ AnniLol Rr.port

PLATE J.

Geol & Nat. Hist. Stir Afinrt.

,C.lt//or/-i.ok.

PJLATE Ji.

Fig. 1. Bosmina striata.

Fig. 2. Bosmina longirostris. (See plate J, fig. 2.)

Figs. 3-5. Bosmina cornuta.

Figs. 6, 7. Pleuroxus procurvatus.

Fig. 8. Graptoleheris inermis.

Fig. 10. Acroperus sp.

Figs. 11, 12. Graptoleheris inermis.

MINNESOTA CRUSTACEA.

From the 10th Annual Report. PLATE J i . Geoh cC- Nat. Hist. Sur. Minn.

P1.ATE K.

Fig.
Fig.
Fig.
Fig.
Fig.

1.
2.
3.
4.
5.

Fig. 6.

Fig. 7.

Fig. 8.

Fig. 9.

Fig. 10.
Fig. 11.
Fig. 12.

Daphnia niinnehaha, male.

" " part of feet of first and second pair.

Canthocamptus hibernicus, antenna of female.

'^ fifth foot of female.

palustris, antenna of male.
frispinosus, fifth foot of female.
■minutus, young.

" nauplius form.
Pseudo-sida hidentata, adult female, antennule, labrum,
augleof shell and post-abdomen.
Daphnia rosea^ young female.
'' " post-imago.

'^ beak.

12 Oi Annual, Rpport

MINNESOTA CRUSTACEA

PLATE K.

GeoL & Nkt. Hist. Sur. Minn.

Q^ti^rrxcK,

PLATE L.

Wig.
Fig.

:Fig.

Fig.

:Fig.

Wig:.

1.

2.
3.
4.

5.

7.

iFig. 8.

Daphnia minnehaha, young female.

" head of female; 2a. post-abdomen.

hi/alina, young female.

young.

' post-imago.
dubia, young.
" older female.

MINNESOTA CRUSJACEA

12 th'Annual Report PLATE L, .

Gcnl & Xai Hist'Sur. ^Iinn.

CJ-Ht-rru:^

PLATE M.

] Fig. 1. Daphnia schceferi, post-abdomen of female.

Fig. 2. " '' - "male.

Fig. 3. " " male antennule.

Fig. 4. " " brain and nerves.

inf. ce. g. infra-oesophagal ganglion with nerves to anten-
nae; ce. oesophagus; n f. frontal nerve; g. opt. optic gang-
lion; ra. opt. muscles which move the eye; p. f. pigment
fleck; n. opt. optic nerve.

Fig. 5. Daphnia scha'fferi, posterior part of embryo.

- Fig. 6, Eiirycercus lamellatus, heart, showing the anterior bifid

portion between the lobes of which is the arterial opening
and valve. The vaned arrows represent deeper currents
while the unvaned indicate superficial ones^ The dotted
line represents the position of the pulsating membrane
separating the venous from the arterial currents and seen
in section at (a).

- Fig. 7. Daphnia similis, anterior part of the nervous system seen

from below, a. optic nerve; b. optic ganglion; c. Irontal
nerve; d. nerve to antennules; e. commissure connecting
upper and lower oesophagal ganglion; f. nerves to antennae
and mandibles.

MINNESOTA CRUSTACEA.

i'^i^ Annual Report

PLATE M.

Geol & Nat. Hist. Sur. Minn.

PLATE N.

Fig. 1-4. Daphnia jmlex, var. nasutiis.

Fig. 5. outliue of head and (a) beak of D. similis.

Fig. 6. Leptodora hyalina, seen from above.

Fig. 7. '' '' larva.

Fig. 8. Latona setifera, female.

Fig. 9. Limnosida frontosa^ female.

Fig. 10. " " auteunule of male.

Fig. 11. Holopedium gibherum, female.

Fig. 12. Sida elongata, head outline.

Fig. 13. Sida cnjstallina, head outline of young female.

Fig. 14. " '' antennule of male.

Fig. 15. '' " '' of female.

Fig. 16. Daphnia galeata, outline of head.

Fig. IT. '' ''vitrea'' " ''' "

MINNESOTA CRUSTACEA.

12 OCAnnualRr^port JlL'ATE 'N. ^^^^ &'J^6i'mst. Sur. Minn.

15

PLATE O.

Fig. 1. Canthocamptus illinoisensis, antenna oMemale.

Fig. 2. " " fifth foot of female.

Fig. 3. " " antennule.

Fig. 4. " '' firstfoot.

Fig. 5. " " caudal stylet.

Fig. 6. CantJiocamptus northumhricus^ var. americanus, fifth

foot of female.
Fig. 7. " " antenna of female.

Fig. 8. " '* maxilliped.

Fig. 9. " " caudal stylet.

Fig. 10. " " antenna of male.

Fig. 11. " " first foot.

Fig. 12. " " fourth foot.

Fig. 13. '' " fifth foot of male.

Fig. 14. " " frontal area.

Fig. 15. CantJiocamptus tenuicaudis, stylets.
Fig. 16. " " fifth foot of female.

Fig. 17. Cyclops serridatus, fifth foot. .
Fig. 18. '" " fourth foot.

Fig. 19. " " outer ramus of first foot.

Fig. 20. Cantliocamptus northumbricus, inner ramus of third

male foot.
Fig. 21. " " beak.

Fig. 22. " " maxilla.

MINNESOTA ^CRUSTACEA.

J2 *>^ Annual Rfport

PLATE O.

Geol & 2^at Hist. Sur'Minn.

PLATE P.

Fig. 1. Heart of Simocephalus vetulus. a, tendons attached to
lateral walls of heart, b, venous opening of heart, c,
muscular bands supporting the abdomen, connected by
transverse bands, d, cells of nutritive matter hiding the
arterial opening, e, thin membrane seen in section
which separates the venous from the arterial blood cur-
rents, is in focus near the side, but its situation in the
center is shown by the dotted line. Above this or out-
side it is the attachment of the powerful antennary
and mandibular muscles, f, posterior arterial sinus, g,
brood-sac. h, alimentary canal with thick glandular
cell walls, i, shell gland or excretory organ, j, power-
ful muscles supporting and moving the abdomen.

Fig. 2. An early stage of the embryo of Daphnia schcefferi. a,
anus, n, nutritive globules or fat drops characteristic
of the summer embryo. m\ m\ outer and inner enve-
lope of the embryo. This is a nauplius stage, but not
the first or proper nauplius. The portion darkly shaded
is nutritive yolk.

Fig. 3. A well advanced winter embryo of Z). scluefferi. a, shell
growing over the eyes. b. c, inner shell, d. outer shell,
e, lateral part of the head, f, antennules. g, labrum.
h, mandibles, i, maxilla, j, second maxilla ? k^, V,
m^, n^, branchial appendages of the 2d-5th pairs of feet,
represented by k, 1, m, n. o, first foot. p. antenna,
q, anus and intestine partly completed, s, shell growing
out from the maxillary region.
Older embryo bursting outer shell.
Egg after extrusion into the brood cavity.
Head of young embryo, a, lenses in formation, b, eyes
appearing as dark flecks, c, shell growing over the
head, d, labrum. e, antennule.
Longitudinal section through an ephippium.
Vertical section through an ephippial Daphnia schcefferi.
Somewhat oblique section through the ephippium (a,
b, c), heart (h), mandibles (m), and labrum (1).

Fig. 10. A vertical section through the ephippium and its egg.

Fig.

4.

Fig.

5.

Fig.

6.

Fig.

7.

Fig.

8.

Fig.

9.

MINNESOTA CRUSTACEA.

J^V} Annual R/'port

PLATE I'.

Gcol & Sat Hist Sur Minn..

PLATE Q.

Fiff

F
F
F
F
F
F
F
F
F
F
F
F
F
F
F
F
F

1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
g.l4.
g. 15.
g.l6.
g.l7.
g. 18.

g

g

Alonella pulchella, female.

" reticulations.
" post-abdomen.
Alona modesta^ male.
Diaptomus similis, female. 5a. jaw.

" fifth foot of male.
" " " " female.
minnetonka, fifth foot of male.
" " " female.
" abdomen of female.

stagnalis, margin of last thoracic segment.
sanguineus, " " " "
stagnalis, fifth foot of the male.
Epischura fiuviatilis, abdomen of male.
" lacustris, fifth feet of male.

'• fiuviatilis, " " " "
Diaptomus pallidus " " " " inner ramus.
" sicilis ''

it

♦ <

Ik

ll

MINNESOTA CRUSTACEA.

I'i'tA Annual Report PLATE Q. Ceol & Xat Hist . Suj: Minn.:-

PLATE Q 1 .

Fig. 1. Diaptomus sp. Young male; external parts as yet but
partly developed showing alimentary and reproductive
systems as well as a portion of the muscular system.
The looped tube is the vas deferens. The small irreg-
ularly coiled tube anteriorly is the shell-gland or
kidney.

Fig. 2. female with ovary , oviducts and heart.

Figs. 3-4. Nauplius larva of same.

Figs. 5-6. fifth pair of feet of male and female.

Fig. 7. mouth appendages, anteriorly the base of antennae fol-
lowed by antennule, labrum, mandible with palp, max-
illa and maxilliped.

^1 MINNESOTA [CRUSTACEA.

From the 10th Annual Report. PTiATE Qi . Geol. <£- Ned. Hist. Sur. Minn,

PLATE Q

Fig.

1.

Osphranticum lahroi

Fig.

2.

antenuule.

Fig.

3.

maxilliped.

Fig.

4.

fifth feet of male.

Fig.

5.

palp of mandible.

Fig.

6.

end of abdomen.

Fig.

7.

feet of first pair.

Fig.

8.

eye.

Fig.

13.

maxilla.

Fig.

14.

mandible.

Fig.

9.

Cyclops afer, female

Fig.

10.

abdomen.

Fig.

11.

maxilliped.

Fig,

12.

antenna.

MINNESOTA CRUSTACEA.

From the ICth Annual Bepori. PLATE Q2. Geoh d- Nat. Hist. Sitr. Minn.

PLATE Q3.

Fig.

1.

Fig.

2.

Fig.

3.

Fig.

4.

Fig.

5.

Fig.

6.

Fig.

7.

Fig.

8.

Fig.

9.

Fig.

10.

Fig.

11.

Fig.

12.

Fig.

13.

Fig.

14.

Cyclops ingens, first segment of abdomen of female.

antenna.

fifth foot.

antenna of young male.

stylets of mature female.

stylets of young male.

niaxilliped.

mandible.

Cyclops Jimbriattis, female.

antenna.

terminal portion of abdomen.

female fifth foot,

second antenna.

Nauplius form.

MINNESOTA CRUSTACEA.

From the 10th Annual Bejjort. PLATE Q3 . Geol. d- Xat. Hist. Sm: Minn.

PLATE Q4.

Fig. 1. Cyclops tenuicornis, female.

Fig. 2. mandible.

Fig. 3. maxillae.

Fig. 4. stylet.

Fig. 5. fifth foot.

Fig. 6. maxillipedes.

Fig. 7. antennae.

Fig. 8. Cyclops '"''signatus,''' abdomen.

Fig. 9. antenna.

Fig. 10. fifth foot.

Fig. 11. male antenna.

Fig. 12. Cyclops parens, abdomen.

Fig. 13. antenna.

Fig- 14. fifth foot.

Fig. 15. Cyclops '''' adolesceiis,"" opening of spermatheea and

cement gland.

Fig. 16. Cyclops '"''adolescens^' abdomen.

Fig. 17. foot.

Fig. 18. antenna of female.

Fig. 19. eye.

Fig. 20. antenna of male.

Fig. 21. C?/c/o;:»s "s?^72cr/?^6-," end of antenna.

MINNESOTA CRUSTACEA.

From the 10th Annual Report. PLATE Q-t. Geol. & Nat. Hist. Sur. Mmn.

PLATE Q 5.

Fig. 1. Cyclops fluviatilis, female.

Fig. 2. antenna.

Fig. 3. antenna of young.

Fig. 4. abdomen of young.

Fig. 5. foot of young.

Fig. 6, foot of adult.

Fig. 7. fifth foot.

Fig. 8. eye.

Fig. 10. C. serrulatus, young.

Fig. 11. Daphtiella hrachyura, female.

Fig. 12. Daphnella brachyiira, male.

Fig. 13. edge of valves.

Fig. 14. abdomen of male.

Fig. 15. abdomen of female.

Fig. 16. antenna of male.

MINNESOTA CRUSTACEA.

From the 10th Annual Report. PLATE Q5 . G^ol. d-Xat. Hist. Sar. Minn.

16

PLATE K.

Fig. 1. Cyclops modestus.

Fig. 2. " " end of abdomen.

Fig. 3. '' " outer ramus of first foot.

Yia, 4. " " ''' " " second foot.

Fi^. 5. " " fifth foot.

Fig. 6. " phaleratus, fourth foot.

Fig. 7. '• " outer ramus of first foot.

Fig. 8. " " fifth foot.

Fig. 9, " " caudal stylets.

Fig. 10. " " antenna of young otherwise perfect.

Fig. 11. " fmbriatus. end of abdomen.

Fig. 12. " diaphanns, abdomen.

Fig. 13. " ater, inner ramus of first foot.

Fig. 14. " " outer '' '' '' ''

Fig. 15. '' " " u u fo^^rtii foot.

Fig. 16. " ''signatus,'^ fourth foot.

Fig. IT. " afe)\ inner ramus of fourth foot.

Fig. 18. '' " st>let.

Fig. 19. " sp.? firstfoot.

Figs. 20, 21. " " terminal segments of fourth foot.

Fig. 22. " " fifth foot.

Fig. 23. Clujdorus glohosus, first foot of male.

MINNESOTA CRUSTACEA

1 'J thAnnLLal Rr.port ^^^ "^^ ^ ■

Geoi <S Nat Hist Sur. Minn.

PLATE S.

Fig.

J..
2.

Fig.

3.

Fig.

4.

Fig.

5.

Fig.

6.

Fig.

7.

Fig.

8.

Fig.

9

Fig.

10.

Fig.

11.

Fig.

12-

Fig.

13.

Ergasilus depressu&, male.

Cyclops oithonoides (Amer. C tenuissimus, var.), stylets.

fifth foot.

" " antennules.

" " fourth feet.

" " antenna of male.

" " brevispinosus, stylet.

" ♦' ''■ inner maxilliped.

" " " swimming foot.

<i

" " fifth foot,

" " antennule.

" » " opening of spermatheca.

Cyclops sp.?, nauplius.

MINNESOTA CRUSTACEA.

'" tf^ Annual Rfport

PLATE S.

GeoL & Xat Hist Sur Minn..

:oRA

PLATE T.

Fig. 1.
Fig. 2.
Fig. 3.
Fig. 4.
lig. 5.
Fig. 6.
Fig. 7.
Fig. 8.
Fig. 9.
Fig. 10.
Fig. 11.
Fig. 12.
Fig. 13.
Fig. 14.
Fia. 15.

Canthocanqjfus minnesotensis, first foot.

stylets.

Ik

antenna of female,
fifth foot of female.

'' '' male,
antenna of male.

Daphnia galeaia^ young.

" " male.

Camptocercus leucocephalus, male,
AloneUa exc'sa, male.
Cyctops insignis, first foot, outer ramus.

fifth foot,

fourth foot.

stylet.
Worm parasitic in arterial sinus of Daphnia schcefferL

I.'

JToTE. On pages 43 and 44, for ' Plate T." read Plate J.

MINNESOTA CRUSTACEA.

1^ th Annual Report

PLATE T.

Gcol & yiU Hist Sun .\finn.

PLATE U.

Fig.

1.

Fig.

2.

Fig.

3.

Fig.

4.

Fig.

5.

Fig.

6.

Fig.

7.

Fig.

8.

Fig.

9.

Fig,

10.

Fig.

11.

Daphnia kalbergensis, of moderate size.
" " antennule of malo.

head of var.
Cyclops thomasi^ fourth foot.

" " outer ramus of first foot.

Daphnia galeata, typical form,
Cyclops thomasi^ fifth foot.

stylet.
Cyclops (insectus?), fourth foot.
Bythotrephes longimanus, female.

A curious large protozoan; a. infundibulum frame work
b. pulsating vacuole; c. nucleus; d. food and digested mat-
ter; e. protective rods; 11a. spicules of the infundibulum.

MINNESOTA CRUSTACEA.

^- i^ Annual Report

'PLATE T^

Geol & yat Hist Sun Minn.

PLATE Ui.

Figs. 1-1 Jr. Limnetes goiddii^-AiYd.
Fig. 15. Daphnia magniceps, female.
Fig. 16. Daphnia minnehaha, female.

MINNESOTA CRUSTACEA.

From the lOth Annual Eeport. PLATE Ui. Geol.d: Nat. Hist. Sur. Minn.

PLATE V.

Fig. 1. Corethra appendicidata, head of larva.

Fio- 2 " " Dortion of heart with its muscles,

a. chitinous projection of the body wall to which are at-
tached two muscular threads; b. peripheral muscle; c.
proximal muscle attached to the wall of the heart; d.
muscles scattered over the surface of the heart, serving
as contractors; e. venous opening.

Fig. 3. do., extremity of body.

Fig. 4. do., abdomen of the pupa.

Figs. 5, 6, 7. Rotifera found with entomostraca in Minnesota.

Fig. 8. Flask-shaped rotifer, hermaphrodite, with eggs and sperm.
a. jaws and head; b. shell gland; c. glandular portion of
the stomach; d. testes; e. oesophagus; f. one of several
embryos.

Fig. 9. jaws of the above.

Fig. 10. similar animal, female, deadly enemy to Chydorus.

Fig. 1 1 . jaws of same.

Figs. 12, 13. ? pedicularis, ecto-parasite of Z)/ap^owMS.

MINNESOTA CRUSTACEA.

^''iifi Annual Report PLATE V.\ GeoLAJ^atHistSurMinrt.

CAH^rricJ^

ot

-5 *

• a

^

^fst:^