Denne Plade, der er eienddniinelic,- for Slægten 

 Lepidurns. er hos nærværende Art ialniindeli^-lied at' 

 forlicddsvis riii;;-e Storrelse o"- som ottest ikke hen- 

 gere end sidste Halesegment er bredt. Formen er 

 mere eller mindre iidpræg-et tuiigedannet. uden nogen 

 bemærkelig Tndsnoring ^■ed Basis. Den \-arierer for- 

 «vrigt særdeles m^get saavel i Storrelse som Form, 

 livad <ler vil kunne sees af de lier givne Figurer 

 (Fig. 21-i — -?T). og tiltager ialmiudidighr(l i La-ngde 

 med Alderen. Fig. 25 fremstiller Halepladen hos et 

 ganske usædvanlig stort Exi'mplar. Det er imidler- 

 tid meget sjeldent, at den naai- en saa betydelig 

 Storrelse som her angivet. Langs efter Midten har 

 hra]e])laden hos alle Individer en stum]i Kjol besat 

 med et nogft varierende Antal af grove Tagger, 



sædvanliijvis 2 eller ?>. Kantr 



T i sin vdre Del 



grovt og noget uregehnæssigt sagtakkede. Hos de 

 tieste FxeiHjilarer harSpidsen af lia!e])laden et lidet 

 Indsnit i 31idten, hvorved dannes i* korte Fiide 

 la]i|)er, der ofte er asymetriske (se Fig. '21). 



1 le sammensatte Øiiie har, som ovenfor anfort, 

 sin IMads paa den mest fremragende i tel af Hovedets 

 Dorsalside (se Tab. XI, Fig. 1 og :•'., Tab. XIII, Fig. 

 1 og 2). De er, i Modsætning til livad Tilfaddet er 

 hos i>ranehipiididerne, sessile, af nyredannet l'^lrm, 

 og saaledes stillede, at deres Forende ligger nær 

 sammen, medens der bagtil mellem dem er et storre 

 L'uiii, Åt'v iiidtages af et o\alt. noget ojihoiet og 

 skarpt begrauidset Felt. den saiikaldte Postoeular- 

 knude I Tab. XIII, Fig. 1, x. Fig. S \ Umiddelbart 

 foran de sammensatte (.)ine ligger det enkle t)ie 

 (Fig. 1, r>. oe), som dog ialmindelighed kun utydeligt 

 skinner igjennem Integumenterne. Hvad de sanunen- 

 satte t)ines Bygning angaar. saa stenuner denne 

 idethele naar afsees fra deres sessile ('haraeter. 

 overens med samme hos Branehipodiderni', skjoiult 

 ogsaa visse I^overensstemmelser kan paavises F^-a 

 det m(U'kebrune Pigment sees talrige sta'rkt lysbry- 

 dende iiegemer at straale ud til alle Sider Disse 

 liegemer er den ydre Del af l\rystalkeglerne, hvis 

 indre sjiid.st udtrukne Del er dybt indplantet i Pig- 

 mentet. Enhver Krystalkegle viser sig ved nærmere 

 Undersogelse iF"ig. (i, 7i at være sammensat af 4 

 Længdesegnu^nter og forbinder sig indad med den 

 tværstriliede Synsstav. hvortil igjen slutter sig en 

 af de mange Kndetibre, hvori Synsnerven o])lo.ser 

 .sig. Ethvert Syns(dement er isoleret ved en mem- 

 branos Skede, i hvis ^lidte sees 2 tydelige, jevn 

 sides liggende Kjernei' (Fig. 7). 



Forste Pai' hdere (Tab. XII. Fig. 1. a ', Fig. 2) 

 udspringer ])aa Hovedets N'entralside til hver Side 

 af Dveila'bens I'asis og umiddelbart bag den halv- 

 maaneformige 1'aiideduplieat ur. De er nu>get smaa 

 og ialmindelighed rettede skraat udåd og fortil, idet 

 de boier sig om I^agkanten af den ovennævnte 



ding posteriorly between the bases of the 2 i-audal 

 filaments. 



This lamella, whieli is ])eenHar to the genus 

 Lrpidunts, is generally, in the present sjieeies, of 

 comparatively snuiU size, measuring as a rule no 

 more in length than the last caudal segment does 

 in breath. The shape is more or less decidedh- lin- 

 giiiform, without any noticeable constriction at the 

 base. Ft also varies very much both in size and 

 shape, as will be seen tVom the figures here given 

 (tigs •>?> — 27). and generally inereases in length with 

 age. Fig. 2.') rejiresents tlie «audal lamella of an 

 unusually large s]ieeimen ; but it is very seldom 

 that it attains to so eonsideral)le a size as that liere 

 shown Tlie caudal lamella in all specimens lias 

 medially a blunt keid armed witli a rather variable 

 number of coarse denticles, generally 2 or '6. The 

 edges are coarsely and rather irregularly dentated 

 in their outer ]K>rtion. in nuist specimens there is 

 a small indentation in the middle of the extremitv 

 of the caudal lanudla, tiius forming 2 short, termi- 

 nal, often asymmetrical jolies (see tig. 27). 



The compound eyes, as above stated, are situ- 

 ated on the most jiromiuent ])art of tlie dorsal sur- 

 face of the iiead (see PI. XI. tigs. 1. ;{; PI. XIII, 

 tigs. 1,2). Unlike those in the Branchipodida', tliev 

 are sessile, reniforiii in shajie, and so jdaced that 

 tiieir anterior ends lie < lose together, while between 

 them posteiiorly there is a considerable s])aee which 

 is occupied b\- an oval, somewhat idevated and 

 sharply-detined field, the so-called post-ocniar tubercle 

 (PI. XJII, fig. 1 X. tig. S|. Immediately in front of 

 the compound eyes lies the ocellus (figs. 1. f), oc); 

 whi( h. however, is generally only indistinctlv .^een 

 tiirough the integuments. \\'ith regard to their 

 structure, the compound eyes, setting aside their 

 .sessile character, agree with those in Branchipodidæ. 

 though a few points of difference can be found. 

 Xumerous strongly refractive iiodies are seen radi- 

 ating to all sides from the dark lirown pigment. 

 These liodies ai'e the outt>r jiart of the cr\-stalline 

 cones, till' inner pointed part being buried deeply 

 in the pigment. Kadi crystalline cone proves, on a 

 closer examination (figs. (I, 7). to be composed of 

 4 longitudinal segments, and to connect itself interi- 

 orly with the tratisversidy barred ocular rod to 

 which, again, one of the numerous terminal fibres, 

 into which the optie nerve resolves itself, is at- 

 tadied. Each visual clement is isolated in a mem- 

 branous sheath, in tiie middle of which are seen 2 

 distinct nuclei lying side by side (tig. 7). 



The first ])air of autennæ (PI. XII. tig. 1. a'. 

 Kg. 2) spring from the ventral .surface of the head 

 on each side of the liase of the ui)per lip. and imme- 

 diately behind the cre.scent-shajied frontal dujilica- 

 ture. They are very small, and are generalh- di- 

 rected obli(|uel\- outwards and forwards, bending 



