120 



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

 enorm Storrel.se, og viser, seet fra Siden, en iiæ.sten 

 halvmaanedannet Form. Det fortsætter sig nedad 

 umiddelbart i et særdeles stort, leformigt krummet 

 Rostrum, der er rettet skraat nedad og bagud. Dets 

 dorsale Kant er kjolformigt tilskjærpet og danner 

 en fuldkommen jeA'n og uafbrudt Biie lige til Spid- 

 .sen af Rostrum. Til liver Side sees en anden meget 

 tydelig 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 hos Cladocererne og navnlig viser 

 en umiskjendelig Lighed med samme hos Lynceiderne, 

 begynder ved Kindbakkernes Fæste og strækker sig 

 herfra med en ganske svag Krumning skraat fortil, 

 henimod Midten af Hovedets Længde, hvorpaa den 

 gjor en meget stærk, næsten vinkelformig Boining 

 og lober skraat bagtil langs Siderne af Rostrum, 

 endende med et kort tandformigt Fremspring i 

 nogen Åfstand fra Spidsen. 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 overBa.sis af Aarerne. 

 Længere nedad nærmer de 2 Kjole sig til hinanden 

 og gjor derved Indtrykket af en tydelig Indknil>ning 

 af Hovedet ved Basis 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. 



Nalckesegmentet (se Tab. XIX, Fig. 1 og 11) 

 er ganske kort og begrændset fra Hovedet ved en 

 vel mai-keret Tværsutur, ved hvis Ender Kindbak- 

 kernes ovre Del er fæstet. Det er ganske svagt 

 hvælvet oventil og viser til hver Side en kort, 

 skraat opadgaaende Ribbe, der paa en Maade er en 

 Fortsættelse af Hovedets laterale Kjole. 



Truncus er omtrent af Hovedets Længde og 

 temmelig tyk fortil, men afsnialnes hurtigt og 

 jevnt bagtil. Den er delt i 12 uniforme Segmenter, 

 hvert bærende et Par Branchialfodder. Dorsalsiden 

 af Segmenterne er ganske glat, uden Borster. Der- 

 imod udgaar fra Siderne af de 2 bagerste Segmenter 

 et Par eiendommelige, lateralt udbredte Plader, hvor- 

 til intet tilsvarende tindes hos andre Phyllopoder. 

 Disse Plader (Fig. 9, 1), som alene foretindes lios 

 Hunnen, er af ikke ubetydelig Størrelse, bladformige, 

 og gaar ud i 3 triangulært tilspidsede Flige, hvoraf 

 den forreste er storst. Ifolge sin Stilling synes de 

 nærmest at være bestemte til at støtte de 2 kage- 

 formige Ægmasser, som bæres linder Skallen. 



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

 enoi'mous size, and \vlien seen from the side, ex- 

 hibits an almost semi-lunar shape. It is continued 

 downwards into an exceedingly lai'ge, falciformly 

 curved rostnim, wliich points obliquely downwards 

 and backwards. Its dorsal margin is sharpened in 

 the form of a keel, and forms a perfectly even 

 and uninterrujited curve right to the point of the 

 rostrum. (_)n each side is visilde another very dis- 

 tinct, and somewhat irregularly wavy keel, b^- 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 notablj' exhil>its an unmistakable resemblance 

 to that in the Lyncei(l(p, commences at tlie place of 

 attachment of the mandibles, and runs thence ^^dth 

 a very gentle curve obli(|uely forwards to about 

 the middle of the length of the head, where 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 from 

 the point. When the head is seen from the front 

 (PI. XVni, fig. 4), this lateral keel appears very 

 prominent in its proximal part, w^here 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 position of the head, as if tripartite at the 

 extremity, being produced in the middle to a strong, 

 mucronate projection, on each side of which is a 

 considerably shorter, dentiform prominence, forming 

 the end of the lateral keel. 



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

 11) is ([uite short and separated from the head by 

 a well-marked transverse suture, to the ends of 

 which the iipper portion of the mandibles is attached. 

 It is very slightly arched above, and shows, on 

 each side, a short, obliquely-ascending bar, which 

 in one way is a continuation of the lateral keel of 

 the head. 



The trunk is of about the same length as 

 the head, and rather thick in front, but tajiering 

 rapidly and evenly behind. It is divided into 12 

 uniform segments, each caiTving a pair of branchial 

 legs. The dorsal surface of the segments is quite 

 smooth, and withoiit bri.stles. On the other hand, 

 from the sides of the two hindmost segments, there 

 issues a pair of peculiar, laterally-extended laminæ, 

 to which there is nothing cox'responding to be found 

 in other Phyllopoda. These laminæ (fig. 9, 1) which 

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

 rable size, are foliate and project into 3 triangularly- 

 pointed lobes, of which the foremost is the largest. 

 Judging from their position, they appear to be 

 intended to support the 2 cake-like masses of 

 that are carried beneath tlie shell. 



