53 
Basaldel er ganske smal og Endedelen sammensat al 12 
rood lange Svommeborster forsynede Led. 
Bagkropslemmerne er af den for Hunnerne al denne 
I ami lie smdvanlige rudimentsere Beskaffenhed, kun dannende 
lancetlormige, med lint cilierede Bprster besatte ubevsege- 
!ige Plader. 
Let midterste Halevedhseng (PL V, Fig. 20) er ;| 1 
et meget eiendommeligt Udseende og uligt sanune bos de 
ovrige bekjendte Mysider. Det er ganske kort, pladelorinigt 
°g nsesten qvadratiskt. kun ubetydeligt afsmalnende mod 
Enden, der i Midten er dybt indskaaret. Indsnittet. der 
onitrent indtager 1 / 3 af Yedhtengets Lamgde. er vinkelformigt, 
med Kanterne nmsten lige, stserkt divergerende og i bele 
s bi Lamgde lint saugtakkede. Paa Spidsen al enliver at do 
triangulate Endefliger staar en enkelt Torn og foran denne 
er til Sidekanterne fmstet en Pad af 8—12 meget sniaa 
lorner, der dog kun naar omtrent til Midten af V edhsengets* 
Laengde. 
Le ydre Halevedhamg (Fig. 21) bar Endepladerne 
temmelig store, af lancetdannet Form og rundt om besatte 
med de smdvanlige Randborster. Den indre Plade er noget 
kortere og smalere end den ydre og viser ved Basis kun 
eu yderlig svag Antydning til det ssedvanligt ber lorekom- 
mende Hpreapparat. Dens indre lvant er under Rand- 
berstorne nrnsten i sin hele Laengde forsynet med en Rad 
al korte Torner. 
Paa det under vor Expedition erlioldte Individ var 
bele Legemet gjennemsigtigt, af hvidagtig F’arve og uden 
( let mindste Spor af nogen Pigmentering. 
Lamgden af det stprste af de to loreliggende Exem- 
plarer synes at have vaeret omkring 35 ram ; men det var 
e ndnu ikke forsynet med tydeligt udviklede iEggeplader og 
ban derfor heller ikke antages at have naaet sin lulde 
Stprrelse. 
Porekomst og Udtoredning. Af denne maerkelige 
%side blev et enkelt Exemplar under Expeditionens sidste 
1 °gt optaget ved Hjselp af Trawlnettet fra det enorme Dyb 
al 1 1 10 Favne i Havet NV af Finmarken (Stat. 295). Det 
11 'det mindre Exemplar blev, som ovenfor anlort, lundet af 
E- Collett i Yentrikelen af Rhodichthys regina, der op- 
t°ges paa den lsengere vestlig beliggende Stat. 297 fra et 
endnu stqrre Dyb, nemlig 1280 Favne. Ogsaa dette Ex- 
emplar var selvfolgeligt incomplet, men viste dog de loi- 
s Kiellig e Kropsvedhaeng bedre vedligeholdte end hos det andet. 
At denne Myside er en i ganske sserlig Grad udprseget 
Dybvandsform. freingaar ikke blot af Findestederne, men 
°gsaa a f Here Punkter i dens Organisation, navnlig de fuld- 
kommen rudimentsere Dine, de tyndelntegumenter og Mangelen 
af Pigmentering. Da begge Stationer tilhorer den kolde Area. 
maa den desudeu antages for at vaere en mgte arktisk Form, 
der rimeligvis er udbredt over hele det dybe Havbasin i 
-bordbavet. 
elongated, being considerably longer than even the stem of 
the leg itself. Its basal part is rather slender, the terminal 
portion consisting of 12 articulations, furnished with long 
natatory bristles. 
The abdominal limbs exhibit the usual rudimentary 
character observed in the females of this family, forming 
merely small, lanceolate, immobile plates, beset with delicately 
ciliated bristles. 
The telson (PI. Y, tig. 20) presents a very peculiar 
appearance, unlike that exhibited in any other known 
Mysidian. It is exceedingly short, lamelliform, and almost 
quadrate, tapering but slightly toward the extremity, which, in 
the middle, appears deeply incised. The incision, which ocupies 
about one-third of the length of the appendage, is angular 
in form, with the margins almost straight, very considerably 
diverging, and, throughout their entire length, finely serrate. 
From the point of each of the triangular terminal lobes, 
springs a single spine, anterior to which are attached along 
the lateral margins a, row of 8—12 very small denticles, reach- 
ing only however to about the middle of the appendage. 
The outer caudal appendages (fig. 21) have the terminal 
plates rather large, lanceolate in form, and beset round the 
edges with the usual marginal bristles. The inner plate is 
somewhat shorter and narrower than the outer, exhibiting 
at the base but an exceedingly faint indication of the audi- 
tory apparatus that usually occurs here. The inner border 
is provided beneath the marginal bristles, throughout its 
entire length almost, with a row of short spines. 
In the specimen obtained on the Expedition, the whole 
body was translucent, whitish, and without the slightest 
trace of pigment. 
The length of the largest of the two specimens ex- 
amined. would appear to have reached about 35"™ ; but as 
yet the animal was not furnished with distinctly developed 
incubatory plates, and can hardly therefore have attained 
its full size. 
Occurrence and Distribution. — 01 this remarkable 
Mysidian. a single specimen was taken, in the trawl, on 
the last cruise of the Expedition, at the enormous depth 
of 1110 fathoms, in the open sea, north-west of Finmark 
(Stat 295). The other and smaller example was, as previ- 
ously stated, found by Mr. R. Collett, in the ventricle of 
Rhodichthys regina. brought up at Stat. 297, lying farther 
west, from a still greater depth — viz. 1280 fathoms. This 
specimen, too, was of course defective, but had the various 
appendages to the body in a better state than the other. 
That the Mysidian treated of here can in a special 
degree lay claim to the character of a true deep-sea form, 
appears not only from the localities where it was met with, 
but also from divers characteristics in its organization, viz. 
the wholly rudimentary eyes, the very thin integuments, and 
the absence of pigment. Both Stations being in the cold area, 
it must, moreover, be regarded as a true Arctic form, dis- 
tributed in all probability throughout the whole of the 
deep basin of the Northern Ocean. 
