11 



ling af klare Pletter (lucid spots), svarende til de 

 enkelte Bundter af Adductormuskelen (se Fig. 1 ms). 

 Nogen virkelig Laasi-and, saaledes som hos Ostra- 

 coderne og enkelte Phyllopoder (Estheria, Limnetis), 

 er imidlertid ikke tilstede, idet de 2 Valvler dorsalt 

 gaar umærkeligt over i hinanden med en jevn Krum- 

 ning. Seet fra Siden (Tab. I, Fig. 1) har Rygskjoldet 

 en noget uregelmæssig oval, eller næsten rhombisk 

 Form, med omtrent samme Høide fertil som bagtil. 

 Rygkanten er ganske svagt buet og danner med de 

 skraat afskaarne bagre Kanter en meget stump Vin- 

 kel. Fortil udgaar fra Rygskjoldet øverst den be- 

 vægelige Pandeplade, som i denne Stilling tager sig 

 ud som et tilspidset, noget nedadboiet Pandeliorn. 

 Imellem denne og de forreste, noget udbuede Kanter 

 af Rygskjoldet er der et smalt Indsnit, hvorfra 

 Øinene rager frem. De nedre Kanter er i sin for- 

 reste Del stærkt buede, længere bagtil næsten lige, 

 og forbinder sig under en stærk Krumning med de 

 bagre Kanter, hvorved fremkommer til hver Side 

 en afrundetSidelap, der næsten rækker lige til Enden 

 af Bagkroppens 4de Segment. Ovenfra seet (Fig. 2) 

 viser Rygskjoldet sig meget smalt og stærkere 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 særegne Muskler kan snart rettes lige 

 ibrtil, snart indbøies mod Forkanten, i hvilket Til- 

 fælde den ligeaom et Laag dækker fortil for Ind- 

 gangen til Rygskjoldets Hule. Rygskjoldet er gan- 

 ske glat, uden nogen tydeligt iidpræget Sciilptur og 

 uden Børster eller Torner, af temmelig tynd, boielig, 

 chitinøs Consistens og halvt gjennemsigtigt, saa at 

 den indenfor liggende Krop tilligemed dens Lemmer 

 kan skimtes igjennem samme. 



For noiere at kunne undersøge denne sidste, er 

 det imidlertid liensigtsmæssigt at fjerne den ene af 

 Rygskjoldets Valvler (se Tab. II, Fig. 1). Det viser 

 sig da, at Legemet i sin hele Længde er tydeligt 

 segmenteret, og at Segmenterne grupperer sig til 

 vel raarkerede Kropsafsnit. Man kan ialt adskille 

 4 saadanne Afsnit, hvoraf de 2 tilhører Forkroppen, ■ 

 de 2 øvrige Bagkroppen. Det forreste Afsnit af 

 Forkroppen kan passende benævnes Hovedet (Cepha- 

 lon), da det, foruden Øinene, kun bærer de 2 Par 

 Folere og de egentlige Munddele (Over- og Under- 

 lælie, Kindbakkerne og 2 Par Kjæver). Dets dorsale 

 Parti, der er af betydelig større Udstrækiyng end 

 dets ventrale, er fast forbundet med Rygskjoldet, 



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 (PI. 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 qi^ite gently 

 curved, and forms with the obliqueU^ truncated 

 posterior margins a very obtuse angle. The mobile 

 frontal plate is.sues 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, biit 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 beliind, where occurs a deep median, 

 sinus narrowly rounded at the bottom, v^hich 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 

 PI. 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 bi'istles 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 PI. 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 antennæ 

 and the oral parts proper (anterior and postei'ior 

 lips, the mandibles and 2 pairs of maxillæ). Its 



