ling af klare Pletter (lucid spots), svarende til de 
enkelte Bundter af Adductormuskelen (se Fig. | ms). 
Nogen virkelig Laasrand, saaledes som hos Ostra- 
coderne og enkelte Phyllopoder (Estheria, Limnetis), 
er imidlertid ikke tilstede, idet de 2 Valvler dorsalt 
gaar umerkeligt over i hinanden med en jevn Krum- 
ning. Seet fra Siden (Tab. I, Fig. 1) har Rygskjoldet 
en noget uregelmessig oval, eller nesten rhombisk 
Form, med omtrent samme Hoide fortil som bagtil. 
Rygkanten er ganske svagt buet og danner med de 
skraat afskaarne bagre Kanter en meget stump Vin- 
- kel. Fortil udgaar fra Rygskjoldet overst den be- 
veegelige Pandeplade, som i denne Stilling tager sig 
ud som et tilspidset, noget nedadboiet Pandehorn. 
Imellem denne og de forreste, noget udbuede Kanter 
af Rygskjoldet er der et smalt Indsnit, hvorfra 
@inene rager frem. De nedre Kanter er i sin for- 
reste Del sterkt buede, lengere bagtil nesten lige, 
og forbinder sig under en sterk Krumning med de 
bagre Kanter, hvorved fremkommer til hver Side 
en afrundet Sidelap, der neesten reekker lige til Enden 
af Bagkroppens 4de Segment. Ovenfra seet (Fig. 2) 
viser Rygskjoldet sig meget smalt og sterkere af- 
smalnende fortil end bagtil, hvor det har en dyb, 
i Bunden smalt afrundet median Indbugtning, der 
skiller de 2 Sidelappe fra hinanden. Ved den for- 
reste Ende af Rygskjoldet sees Pandepladen, som 
nu viser “en smal tungedannet Form, med Enden 
jevnt afrundet (se ogsaa Tab. II, Fig. 2). Den er 
forbundet med Rygskjoldet ved et tydeligt Led, saa 
at den ved seregne Muskler kan snart rettes lige 
fortil, snart indboies mod Forkanten, i hvilket Til- 
feelde den ligesom et Laag dekker fortil for Ind- 
gangen til Rygskjoldets Hule. Rygskjoldet er gan- 
ske glat, uden nogen tydeligt udpreget Sculptur og 
uden Borster eller Torner, af temmelig tynd, boielig, 
chitines Consistens og halvt gjennemsigtigt, saa at 
den indenfor liggende Krop tilligemed dens Lemmer 
kan skimtes igjennem samme. 
For noiere at kunne undersege denne sidste, er 
det imidlertid hensigtsmessigt at fjerne den ene af 
Rygskjoldets Valvler (se Tab. II, Fig. 1). Det viser 
sig da, at Legemet i sin hele Lengde er tydeligt 
segmenteret, og at Segmenterne grupperer sig til 
vel markerede Kropsafsnit. Man kan ialt adskille 
4 saadanne Afsnit, hvoraf de 2 tilhorer Forkroppen, 
de 2 evrige Bagkroppen. Det forreste Afsnit af 
Forkroppen kan passende benzevnes Hovedet (Cepha- 
lon), da det, foruden Minene, kun berer de 2 Par 
Folere og de egentlige Munddele (Over- og Under- 
lebe, Kindbakkerne og 2 Par Kjever). Dets dorsale 
Parti, der er af betydelig storre Udstrekning end 
dets ventrale, er fast forbundet med Rygskjoldet, 
11 
a well defined oval area, in which are observed a@ 
number of lucid spots corresponding to the indivi- 
dual bundles of the adductor-muscle (see fig. 1, ms). 
A true cardinal margin, such as appears in the 
Ostracods and some Phyllopods (Estheria, Limnetis), 
does: not, however, exist, as the 2 valves pass dor- 
sally, imperceptibly into each other by an even 
curvature. Viewed laterally (Pl. I, fig. 1) the cara- 
pace has a somewhat irregular oval or almost 
rhomboid form, having nearly the same height in 
front as behind. The dorsal margin is quite gently 
eurved, and forms with the obliquely truncated 
posterior margins a very obtuse angle. The mobile 
frontal plate issues anteriorly from the upper part 
of the carapace, and in this situation appears as 
an acuminate, somewhat downwards-bent rostrum. 
Between it and the foremost somewhat bulging edges 
of the carapace, there is a narrow incision from 
which the eyes project. The lower edges are in 
their foremost portion greatly curved, but further 
back almost straight, and unite with a strong curve to 
the posterior edges, whereby is formed on each side a 
rounded lateral lobe that almost extends to the extrem- 
ity of the 4th segment of the posterior division of the 
body. Viewed from above (fig. 2) the carapace ap- 
pears very narrow and diminishing more rapidly 
in front than behind, where occurs a deep median, 
sinus narrowly rounded at the bottom, which sepa- 
rates the 2 lateral lobes from each other. At the 
foremost extremity of the carapace appears the fron- 
tal plate, which now exhibits a narrow linguiform 
shape with the extremity evenly rounded (see also 
Pl. II fig. 2). It is connected to the carapace by 
a distinct articulation, so that it can by means of 
special muscles be directed, now straight forward 
now bent in towards the anterior margin, in which 
case it, like a lid, covers in front the entrance to 
the cavity of the carapace. The carapace is per- 
fectly smooth, without any distinctly marked sculp- 
' ture, and is devoid of bristles or spines; of rather 
thin, flexible, chitinous consistency and semi-trans- 
parent, so that the enclosed body with its appen- 
dages may be observed through it. 
In order to closely investigate the last-named, 
it becomes desirable to remove the one of the valves 
of the carapace (see Pl. II fig. 1); it then appears, 
that the body throughout its entire length is dis- 
tinctly segmented, and that the segments group 
themselves into well defined sections of the body. 
We are able to distinguish in all 4 such sections, 
of which 2 pertain to the anterior division, and the 
other 2 to the posterior division of the body. The 
front section of the anterior division of the body 
may be suitably termed the head (cephalon), as it, 
besides the eyes, only bears the 2 pairs of antenne 
and the oral parts proper (anterior and posterior 
lips, the mandibles and 2 pairs of maxille). Its 
