2 4 



dannet til en kraftig tilspidset og svagt krummet Eiuleklo. 

 Begge disse Fodpar er temmelig rigeligt besatte med korte 

 Børster. 



Gjellernes Antal er (sp Fig. 21) 5 paa hver Side. 

 svarende til de 5 Par Fødder. I sin Bygning og Udseende 

 viser de intet usædvanligt. 



Bagtroppens Svømmevedhæng (Fig. 24—25) er kraftigt 

 udviklede og rettede noget skraat udåd til Siderne, saa at 

 deres ydre Del viser sig. naar Dyret sees ovenfra (Fig. 1). 

 ragende frem til hver Side. De bestaar a f en særdeles tyk 

 og muskuløs Rodde! eller Stamme, til hvis Ende er ind- 

 leddel 2 uligestore Grener. Den ydre af disse er storst, 

 dannende en langs Kanterne tæt borstebesat, lancetformig 

 Plade af Stammens dobbelte Længde. Den indre Gren er 

 neppe mere end halvt saa lang. paa Iste Par uleddet, paa 

 de øvrige bestaaende af to tydelige Segmenter. Paa de to 

 forreste Par er denne (iren noget ulige hos begge Kjøn. 

 Hus Hunnerne er den paa Iste Par (Fig. 24) af elliptisk 

 Form. men noget vreden, saa at den vanskeligt kan ud- 

 bredes i samme Plan. Hos Haunerne er den (Fig. 26) 

 derimod tydelig indknebet paa Midten og noget udvidet i 

 hver Ende. samt her forsynet med lange og stive, ucilierede 

 Børster. Paa 2det Par er denne (iren hos Hunnerne (Fig. 

 25) fuldkommen af samme Udseende som paa de følgende, 

 bestaaende af 2 med hinanden knæformigt forbundne Seg- 

 menter, hvoraf det yderste er længsl og smalt lancetformigt. 

 Hos Hannerne har den (Fig. 27) et temmelig afvige.nde 

 Udseende. Den bestaar vistnok ogsaa her af 2 Segmenter, 

 men det yderste er her tvedelt eller gaar ud i to ulige 

 lange, med stærke Borster besatte Lapper. 



Det midterste Halevedhæng (Fig. 28). der egentlig 

 forestiller Bagkroppens sidste Segment, er af smal. lancet- 

 dannet form og oventil langs ad Midten noget udhulet. 

 med to stumpe Sidekjøler, hvoraf enhver bag Midten hæver 

 sig til 2 skarpe tornformige Fortsatser. Enden er udtrukket 

 til en triangulær Spids. og til hver Side af denne er ind- 

 leddet en kort Torn. Langs ad Sidekanterne af Vedhænget 

 tindes desuden en tæt Kad af Fjærbørster. 



De ydre Halevedhæng (Fig. 28). der sammen med 

 det midterste danner den saakaldte Halevifte. bestaar af 

 en kort. paa Ydersiden i en stærk tornformig Fortsats 

 udgaaende Eoddel og to omtrent lige lange pladeformige 

 (irene. Den ydre af disse er noget bredere end den indre 

 og har den ydre Kant glat samt lohende bagtil ud i en 

 stærk Torn. hvorfra en tydelig Sutur strækker sig paaskraa 

 tværsover Pladens ydre Del. Kanterne er forøvrigt paa 

 begge Grener forsynede med en regelmæssig Kad af korte 

 Fjærbørster. Den ovre Flade er paa den ydre Gren for- 

 t med to. paa den indre med en enkelt stump Længdekjøl. 



Farven er i levende Tilstand overalt rødlig brun, som 



larger than the 5th. The la>t segment is transformed into 

 a strong, pointed, and slightly curved terminal claw. Both 

 these pairs of legs are rather closely beset with short 

 bristles. 



The branchiæ (see fig. 21) are "i in number on either 

 side. corresponding to the 5 pairs of feet. In their structure 

 and appearance they exhibit nothing uncommon. 



The natatory appendages of the abdomen (figs. 24. 



25) are powerfully developed and directed somewhat obliquely 

 sideways: hence. their exterior part appears, when the 

 animal is viewed from above (fig. 1). to project out from 

 either side. They consist of an exceedingly thick and 

 muscular basal portion, or stem. to the end of which are 

 jointed in 2 branches of unequal size. The outer branch is 

 the larger. constituting a lanceolate plate, twice the length 

 of the stem. and thickly beset with bristles along the edges. 

 The inner branch is scarcely half as long; on the Ist pair 

 it has no articulations. on the others it consists of two 

 disthict segments. On the 2 foremost pairs, this branch 

 differs somewhat in the 2 sexes. In the females, it has on 

 the Ist pair (fig. 24) an elliptic form. but is somewhat twisted, 

 so as with difficulty to admit of being spread out in the 

 same plane. In the males, on the other hand. it is (Hl. 



26) distinctly constricted in the middle, and somewhat ex- 

 pauded at either extremity. as also furnished with long and 

 stift' unciliated bristles. On the 2nd pair, this branch is 

 in the females (fig. 25) of precisely the same appearance 

 as on those succeediug it, consisting as it does of 2 con- 

 nected geniculate segments, of which the outer one is the 

 longer, and narrow lanceolate. In the males, it exhibits 

 (fig. 27) a rather different appearance. True. it consists 

 ul 2 segments; but the outer one is bipartite, or protends 

 in 2 lobes of unequal length. lieset with strong bristles. 



The telson (fig. 28). that strictly represents the last 

 segment of the abdomen. is slender, lanceolate in form, 

 and somewhat hollowed out above. along the middle part, 

 with two obtuse lateral carinæ. each of which. posterior to 

 the middle. rises as an acute spiniform prolation. The 

 extremity is drawn out to a sharp triangular point, on 

 either side of which is jointed in a short spine. Extending 

 along the lateral borders of the appendage, occur moreover 

 a close-set series of plumose bristles. 



The exterior caudal appendices or uropoda (fig. 29), 

 which. togetber with the telson. form the so-called caudal 

 fan. consist of a short basal part, produced on the outer 

 side as a strong spiniform prolation. and of two lamellar 

 branches about equal in length. The outer of these 

 branches is somewhat hroader than the inner. with the 

 exterior margin smooth and projecting posteriorly as a 

 powerful spine. whence a distinct suture passes obliquely 

 straight across the outer portion of the plate. For the 

 rest. the hurders of both branches are furnished with a 

 regular series of short plumose bristles. On the upper 

 surface of the outer branch occur two obtuse. longitudinal 

 carinæ, on that of the inner a single one. 



Colour in a hvina state evervwhere reddish-hrown. as 



