32 
med Spidsen noget bueformigt fortilkrummet. Deres Byg- j 
ning er forovrigt den ssedvanlige. 
Bagkroppens Svommevedhxeng (Fig. 17 — 20) er vel 
udviklede og som ssedvanligt bestaaende af en tyk og musk- 
ulo's Basaldel og 2 Grene. Den indre af disse er paa lste 
Par (Fig. 17) saxrdeles kort af oval Form og langs Kanternc 
tad besat med divergerende Fjasrborster. Hos Hannerne 
har denne Gren (se Fig. 19) en noget mere uregelmsessig 
Form end hos Hunnerne og er ved Enden forsynet med 
et sseregent smalt Appendix. Paa de ovrige Par (se Fig. 
18) er denne Gren vel udviklet, af lancetdannet Form lige- 
som den ydre og langs Kanterne besat med en enlcelt Rad 
af stxerke Fjaerborster. hvortil endnu kommer et lidet smalt 
cvlindriskt Appendix, der er fsestet til den indre Kant foran 
Midten. Paa 2det Par er hos Hannerne (se Fig. 20)' dette 
Appendix dobbelt. 
Det midterste Halevedkseng (Fig. 21) er stserkt for- 
lsenget, betydelig kengere end sidste Segment, og temmelig 
smalt, jevnt aftagende i Brede mod Spidsen, som er tvsert 
aflcuttet og i Midten svagt, men tydeligt udrandet samt til 
hver Side af Udrandingen bevsebnet med 2 saerdeles korte 
Torner (se Fig. 22). Langs Sidekanterne af Vedhsenget 
bemaerkes endnu paa hver Side en Rad af 4 meget smaa 
tandformige Fremspring ligesom en Del korte Bprster. 
De ydre Halevedliamg (Fig. 23). bvis korte Roddel 
gaar ud i en stserk bagudrettet Fortsats. bar Endepladerne 
meget ulige udviklede. idet den indre er betydelig baade 
kortere og smalere end den ydre. Denne sidste viser et 
tydeligt afsat Endesegment og bar den ydre Kant fuld- 
kommen lige samt bagtil gaaende ud i en stank tornformig 
Fortsats. 
Farven er i levende Tilstand sserdeles brillant, nemlig 
overalt smukt morgenrod, noget intensere ved Enden af 
hvert Bagkropssegment. Over Midten af Rygskjoldet be- 
mserkes desuden et stprre uregelmaessigt sadelformigt Felt 
af en mork blaa.bg Farve. Oinenes Pigment er. som oven- 
for anfprt ganske lyst, opakt bvidt, og stikker mserkebgt af 
mod de intensivt rodfarvede 0ienstilke. Artsbensevnelsen 
“ leucopis ” er lientet berfra. 
Lcmgden af det storste erholdte Exemplar er, maa.lt 
fra Enden af 2det Par Fpleres Blad til Spidsen af det 
midterste Halevedbamg 95 mw , en Stprrelse der langt over- 
gaar samme hos de pvrige bekjendte Arter af Skegten. 
Udvikling. Paa et af de indsamlede Exemplarer 
fandtes under Bagkroppen fuldmoden Rogn, og jeg fik her- 
ved Anledning til at anstille nogle Undersogolser over Ud- 
viklingen. Allerede hos den i'orst opdagede Art, B. sim- 
pMdrostris, bavde iEggenes ualmindelige Storrelse vseret mig 
paafaldende og ledet mig paa den Tanks, at dette maaske 
kunde antyde en eiendommelig Udviklingsmaade bos nser- 
vserende Skegt. En lignende paafaldende Storrelse bavde 
iEggene ogsaa hos det undersogte Exemplar af den her 
ombandlede Art (se Fig. 2), og beldigvis befandt de sig 
her netop i det sidste Udviklingsstadium, saa at den ind- 
sluttede Unge tydeligt kunde skimtes igjennem den tynde 
considerably larger than any of the others, and has a some- 
what bow-shaped, anteriorly curving point. 
The natatory appendages of the abdomen (figs. 17 — 20 ) 
are well developed, consisting as usual of a thick and muscular 
basal portion and 2 branches. The inner of these branches 
is on the 1st pair exceedingly short, and densely beset along 
the margins with diverging, plumose bristles. In the males, 
this branch (see fig. 19) has a somewhat more irregular 
form than in the females, and is furnished at the extremity 
with a. peculiar, narrow appendix. On tbe other pairs (see 
fig. 18), this branch is well developed, lanceolate in form, 
like the outer, and beset along the margins with a single 
sei’ies of strong, phimose bristles, as also provided with a 
small, narrow, cylindric appendage, attached, anterior to 
the middle, on the inner margin. In the males (see fig. 
20), the 2nd pair have this appendix double. 
The telson (fig. 21) is greatly prolonged, considerably 
longer than the terminal segment, and rather narrow, gradu- 
ally diminishing in breadth toward the point, which is 
abruptly truncate, and in the middle slightly, but distinctly, 
emarginate, as also, on either side of the emargmation, 
armed with 2 exceedingly short spines (see fig. 22). Along 
the lateral borders of the telson are observed on either side 
a. row of 4 exti’emely small, dentiform projections, together 
with a number of short bx’istles. 
The exterior caudal appendages (fig. 23), whose short 
basal part extends as a strong, posteriorly directed projec- 
tion, have the terminal plates very unequally developed, the 
inner one being alike shorter and narrower than the outer. 
The latter plate exhibits a distinctly developed terminal 
segment, and has its outer margin perfectly straight, ex- 
tending posteriorly as a strong, spiniform projection. 
Colour , in a living state, exceedingly brilliant, every- 
where a magnificent i*osy red, a trifle more intense at the 
end of each segment of the posterior division of the body. 
Extending across the middle of the carapax, is observed 
moreover a large, irregular, saddle-shaped area, of a dark- 
bluish colour. The ocular pigment is, as stated above, 
wholly colourless, viz. an opaque white, and forms a striking 
contrast to the intensely red-coloured eye-stalks. The generic 
appellation “leucopis” is taken from the said characteristic. 
Length of tbe largest specimen, measured from the 
end of the scale of the 2nd pair of antennae to the point 
of tbe telson, 95”™. a size very considerably exceeding that 
observed in any other species of tbe genus. 
Development. — In one of the specimens collected, 
mature roe was found beneath the abdomen, which afforded 
opportunity of examining the development of the animal. 
On tbe discovery of the first species, B. simplicirostris, I 
had been struck by the unusual size of the eggs, and led 
to surmise that possibly it might indicate a peculiar mode 
of development in tbe present genus. The size of the eggs 
was equally striking in the specimen I examined of the species 
treated of here (see fig. 2): fortunately, too, they had reached 
the last stage of development; and hence, the brood could 
be distinctly discerned through the delicate membrane (see 
figs. 24, 25). as also without great difficulty removed from 
