120 



Hovedet (se Tab. XIX, Fig. 1 og 11) er af 

 enorm Storrelse, og viser, seet fra Siden, en næsten 

 halvmaanedannet Form. Det fortsætter sig nedad 

 umiddelbart i et særdeles stort, leformig-t knimmet 

 Eostrum, der er rettet skraat nedad og bagud. Dets 

 dorsale Kant er kjolformigt tilskjærpet og danner 

 en fuldkoramen jevn og nafbrudt Bue lige til Spid- 

 sen afEo.strum. Til liver Side sees en anden meget 

 tvdelig og noget uregelmæssig bugtet Kjol, hvorved 

 Hovedets Sideflader deles i en dorsal og en ventral 

 Area. Denne Kjol, der aabenbart svarer til den 

 saakaldte Fornix lu)s Cladocererne og navnlig viser 

 en umiskjendelig Lighed med samme hos Li/nceiderne, 

 begvnder ved Ivindbakkernes Fæste og strækker sig 

 herfra med en ganske svag Krumning skraat fortil, 

 henimod Midten af Hovedets Længde, hvorjjaa den 

 gjor en meget stærk, næsten vinkelformig Boining 

 og lober skraat bagtil langs Siderne af Rostrum, 

 endende med et kort tandformigt Fremspring i 

 nogen Afstand fra S]>idsen. Sees Hovedet lige for- 

 fra (Tab. XVIII, Fig. 4), viser denne laterale Kjol 

 sig stærkt fremspringende i sin proximale Del, idet 

 den her som et Hvælv dækker over Basis af Aarerne. 

 Længere nedad nærmer de 2 Kjole sig til hinanden 

 og gjor derved Indtrykket af en tvdelig Indknibning 

 af Hovedet ved Ba.sis af Rostrum. Dette sidste 

 viser sig i denne Stilling af Hovedet ligesom tredelt 

 i Enden, gaaende i Midten ud i en stærk dolk- 

 formigt tilspidset Fortsats, og til hver Side af 

 denne i et betydelig kortere tandformigt Fremspring, 

 der danner Enden af de laterale Kjole. 



Nakkesegmentet (se Tab. XIX, Fig. 1 og U) 

 er ganske kort og begrændset fra Hovedet ved en 

 vel markeret Tværsutur, ved hvis Ender Ivindbak- 

 kernes ovre Del er fæstet. Det er ganske svagt 

 hvælvet oventil og viser til hver Side en kort, 

 skraat opadgaaende Ribbe, der ])aa en Maade er on 

 Fortsættelse af Hovedets laterale Kjole. 



Truncus er omtrent af Hovedets I^ængde og 

 temmelig tyk fortil, men afsmalnes hurtigt og 

 jevnt bagtil. Den er delt i 12 uniforme Segmenter, 

 li vert 1 lærende et Par Branehialfodder. Dorsalsiden 

 af Segmenterne er ganske glat, nåen Borster. Der- 

 imod udgaar fra Siderne af de 2 bagerste Segmenter 

 et Par eiendommelige, lateralt udliredte Plader, hvor- 

 til intet tilsvarende findes hos andre Phyllopoder. 

 Disse Plader (Fig. 1), 1), som alene forefindes hos 

 Hunnen, er af ikke ubetydelig Storrelse, bladformige, 

 og gaar ud i .'5 triangulært tilspidsede Flige, hvoraf 

 den forreste er storst. Ifolge sin Stilling synes de 

 nærmest at være bestemte til at stotte de 2 kage- 

 formige Ægmasser, som bæres under Skallen. 



The head (see Pl. XIX, figs. 1 and 11) is of 

 enormous size, and when seen from the side, ex- 

 hibits an almost semi-lunar slmpe. It is continued 

 downwards into an exceedingly large, falciformly 

 curved rostrum, which points obli(|uely downwards 

 and backwards. Its dorsal margin is sharpened in 

 the form of a keel, and forms a perfectlj' even 

 and uninterrupted curve right to the point of the 

 rostrum. On each side is visible another very dis- 

 tinct, and somewhat irregularly wavy keel, by which 

 the lateral surfaces of the head are divided into a 

 dorsal and a ventral area. This keel, which evi- 

 dently answers to the so-called fornix in Cladocera, 

 and notably exhilnts an unmistakable resemblance 

 to that in the Li/ncc/chp, commences at the place of 

 attachment of the mandibles, and runs thence with 

 a very gentle curve obliquely forwards to about 

 the middle of the length of the head, wliej'e it 

 makes a very sharp, almost angular bend, and runs 

 backwards along the sides of the rostrum, ending 

 in a short, dentate projection at some distance fr(un 

 the jioint. When tlie head is seen from the front 

 (PL XVIII. hg. 4), this lateral keel appears- very 

 prominent in its proximal part, where it covers the 

 base of the oars like an arch. Farther down, the 

 2 keels approach one another, thereby giving the 

 impression of a distinct contraction of the head at 

 the base of the rostrum. The latter appears, in 

 this po.sition of the head, as if tripaz'tite at the 

 extremit)', being produced in the middle to a strong, 

 mucronate projection, on each side of which is a 

 considerably shorter, dentiform prominence, forming 

 tlie end of the lateral keel. 



The cervical segment (see PI. XIX, tigs. 1 and 

 11) is quite short and separated from the Iiead by 

 a well-marked transverse suture, to tlie ends of 

 which the upper portion of the mandibles is attached. 

 It is very slightly arched .above, and shows, on 

 each side, a short. obli(|uel3'-ascending bar, which 

 in one way is a continuation of the lateral keel of 

 the liead. 



The trunk is of about the same length as 

 the head, and rather thick in front, but tapering 

 rapidly and evenly liehind. It is divided into 12 

 uniform segments, eacli carrying a ])air of brancliial 

 legs. The dorsal surface of tlie segments is quite 

 smootli, and without bristles. On the otlier liand, 

 from tlie sides of the two liin(hnost segments, there 

 issues a pair of peculiar, laterally-extended lamina', 

 to which there is nothing corresponding to be found 

 in other Phvllopoda. These laminæ (tig. 'J, 1) which 

 are only found in the female, are of no inconside- 

 rable size, are foliate and project into 3 triangularl}-- 

 pointed lobes, of which the foremost is the largest. 

 .ludging from their position, they appear to be 

 intended to sujiport the 2 cake-like masses of eggs 

 that are carried beneath the shell. 



