Gen. Limnadia, Brogniart, 1820. 
Slegtscharacteristik. —Skallen steerkt sammen- 
trykt, meget tynd, glat, uden tydelige Umboner, men 
hos det voxne Dyr med talrige Veextstriber. Hove- 
det forholdsvis lidet og forsynet med et stilket dor- 
salt Fastheftningsorgan, Pandedelen konisk frem- 
springende og sondret fra Rostrum ved en vinkel- 
formig Indbugtning. Foddernes Antal omkring 24 
Par, den dorsale Lap af Exopoditen kun lidet frem- 
ragende; Epipoditen forholdsvis liden. Halepladerne 
udtrukne nedentil i et tilspidset, ikke kloformigt 
Hjorne og fint tandede bagtil. De sammensatte 
Mine tydeligt adskilte, skjondt tet sammenstillede; 
det enkle Mie triangulert. Forste Par Folere for- 
holdsvis korte, men tydeligt lappede i sin ydre Del; 
2det Par med den indre Gren lengere end den ydre, 
begge delte i talrige skiveformige Led, besatte i 
den indre Kant med lange Syommeborster, i den 
ydre med korte Pigge. Aiggene meget smaa, om- 
givne af en turbinformet Skal. Forplantningen ude- 
lukkende parthenogenetisk. Udviklingen en complet 
Metamorphose. 
Bemerkninger. — Slegten Limnadia blev forst 
opstillet af Brogniart allerede i 1820, medens Sleg- 
ten Hstheria daterer sig fra en langt senere Tid, 
hvorfor ogsaa Familien bor beneevnes efter den for- 
ste og ikke, som det ofte er skeet, efter den sidste 
Slegt. Fra Slegten Hstheria er nerverende Slegt 
let kjendelig ved den sterkere sammentrykte og 
tyndere Skal, paa hvilken ingen tydelige Umboner 
findes, ved Hovedets meget forskjellige Form, tildels 
ogsaa ved iste Par Foleres, Foddernes og Hale- 
pladernes Structur. Meget nermere staar den Sleg- 
ten Hulimadia Packard, og den eneste mere vesent- 
lige Forskjel synes at vere, at Arterne af denne 
sidste Slegt er, ligesom de af Sl. Estheria, bisexuelle, 
medens Hanner af Sl. Limnadia endnu ikke, trods 
de omhyggeligste Efterforskninger, er forefundne og 
rimeligvis heller ikke existerer. Man kjender hidtil 
med Sikkerhed kun 2 Arter af denne Slegt, en euro- 
peisk og en amerikansk, LZ. americana Morse. De 
svrige til denne Slegt henregnede Arter synes alle 
at henhore til den neerstaaende Slegt, Hulimadia. 
Limnadia lentiecularis (Lin) 
(Pl. XIV—XVII). 
Monoculus lenticularis, Linné, Fauna Svecica, Edit. 2da, p. 499. 
Daphnia gigas, Herman, Mém. apterol. p. 134, Pl. V, fig. 4, 5, 
Pigs fig. 2. 
Limnadia Hermanni, Brogniart, Mém. du Mus. d’hist. nat., 
Tome VI, p- 84, PI. 18: 
Limnadia gigas, Grube, Archiv f. Naturgeschichte, 19 Jahrg., 
Bd. 1, p. 164. 
Artscharacteristik. — Skallen, seet fra Siden, 
bredt oval, med den storste Hoide foran Midten, 
85 
Gen. Limnadia, Brogniart, 1820. 
Generic Characters. — Shell greatly compressed, 
very thin, smooth, without distinct umbones, but 
with numerous lines of growth in the full-grown 
animal. Head comparatively small and furnished 
with a stalked dorsal affixing organ; frontal part 
conically projecting, and defined from the rostrum 
by an angular sinus. Number of feet, about 24 
pairs; dorsal lobe of the exopodite only slightly 
projecting; epipodite comparatively small. Candal 
lamellae drawn out below to a sharp, not clawlike 
angle, and finely dentated posteriorly. Compound 
eyes quite distinct from one another, though placed 
close together: ocellus triangular. First pair of 
antenne comparatively short, but distinctly lobed 
in their distal portion; 2nd pair with the inner 
ramus longer than the outer, and both divided into 
numerous laminar joints, clothed on the inner edge 
with long natatory bristles, on the outer with 
short spines. Ova very small, surrounded by a 
turbinate shell. Propagation exclusively partheno- 
genetic. Development a complete metamorphosis. 
Remarks. — The genus Limnadia was first 
established by Brogniart as early as 1820, while 
the genus Hstheria dates from a much later time. 
The family ought therefore to be named after the 
first genus, and not, as is so often done, after the 
last. The present genus is easily distinguishable 
from Lstheria by the greater compression and 
thinness of its shell, on which no distinct umbones 
are to be found; by the very different form of the 
head; and to some extent by the structure of the 
1st pair of antenne, the legs, and the caudal lamelle. 
The genus Eulimadia, Packard, is far more closely 
allied, and the only essential difference seems to be 
that the species of this last genus, like those of the 
' genus Lstheria, are bi-sexual, while males of the 
genus Limnadia, in spite of the most careful investi- 
gations, haye not yet been found, and probably do 
not exist. Only two species of this genus are as 
yet known, one European and one American, L. 
americana, Morse. The other species referred to 
this genus would seem all to belong to the nearly- 
allied genus, Eulimadia. 
Limnadia lenticularis (Lin.) 
(Pl. XIV—XVID. ; 
Monoculus lenticularis, Linneus, Fauna Svecica, Edit. 2da, 
p. 499. 
Daphnia gigas, Herman, Mém. apterol. p. 134, Pl. V, figs. 4,5; 
Pl. IX, fig. a. 
Limnadia Hermanni, Brogniart, Mém. du Mus. d’hist. nat. 
Tome VI, p. 84, Pl. 13. 
Limnadia gigas, Grube, Archiv f. Naturgeschichte, 19de Jahrg. 
Bad. I, p. 154. 
Specific Characters. — Shell, seen from the 
side, broadly oval, with the greatest height in front 
