10 
son. 
observeret af andre Forskere. Fra den folgende 
meget nerstaaende, skjondt sikkert specifiskt for- 
skjellige Form er den strax kjendelig ved de vel 
udviklede og med tydeligt Pigment og Synselementer 
forsynede Mine, samt ved Pandepladens forskjellige 
Form. 
Beskrivelse af Hunnen.. 
- Legemets Lengde, regnet fra Spidsen af Pande- 
pladen til Enden af de sammenlagte Halegrene, er 
hos de sterste af mig observerede Exemplarer, tagne 
ved Lofoten, omtrent 12 mm. Exemplarer fra vor 
Syd- og Vestkyst er ialmindelighed noget mindre. 
Legemets Form (se Tab. I, Fig. 1 og 2) maa 
idethele siges at vere temmelig slank, iser naar . 
man observerer Dyret i levende Tilstand. Paa de 
i Spiritus opbevarede Exemplarer synes ialmindelig- 
hed Legemet noget kortere og mere undersetsigt 
paa Grund af en ved Spiritusens Action frembragt 
kjendelig Contraction i Ledfoiningerne mellem de 
forskjellige Segmenter; noget der ogsaa bemerkes 
paa de fleste af andre Forskere givne Figurer af 
dette Dyr. Hele den forreste Halvpart af Legemet 
dekkes mere eller mindre fuldstendigt af Rygskjol- 
det, bag hvilket den bagtil successivt afsmalnende 
og meget bevegelige Hale rager frit frem. Den 
habituelle Lighed med en Copepode (navnlig visse 
Herpacticider) er umiskjendelig og bliver endmere 
paafaldende, naar man observerer Dyret i levende 
Tilstand, idet Bevegelserne foregaar paa en fuld- 
kommen lignende Maade. 
Rygskjoldet er meget sterkt sammentrykt fra 
Siderne, saa at dets Brede kun lidet overgaar den 
halve Heide, og, da det desuden mellem sine Side- 
dele fuldstendig indeslutter ikke blot Munddelene, 
men ogsaa alle folgende Forkropslemmer (Branchial- 
fodderne), har .det mere Lighed med en tveklappet 
Skal, saaledes som vi finder det hos visse Phyllo- 
poder og Cladocerer. Ogsaa i andre Henseender er 
denne Lighed tydeligt fremtredende. Saaledes vil 
man finde, at dette Rygskjold kun paa et meget 
indskrenket Omraade helt fortil og oventil, dan- 
ner den umiddelbare Kropsveg (se Tab. II, Fig. 1), 
medens det forovrigt kun ganske lost dekker Le- 
gemet, som dertor frit kan beveges indenfor samme. 
Endelig kan de 2 Sidedele, eller Valvler, ligesom 
hos de ovennevnte Branchiopoder, beveges imod 
hinanden ved Hjelp af en sterk transversal Ad- 
ductormuskel (Tab. II, Fig. 7, ms), der lige bag 
Munddelene forbinder de 2 Valvler med hinanden. 
Insertionen af denne Adductormuskel er ogsaa ud- 
vendigt meget tydeligt at se i den forreste Del af 
hver Valvel, nermere Dorsalsiden, i Form af en vel 
begrendset oval Area, hvori bemerkes en Ansam- 
Overhovedet synes kun denne ene Art at vere | Altogether, only this single species appears to have 
been observed by other investigators. From the 
following very closely related, although certainly 
specifically different, form, it is immediately distin- 
guishable by the well developed eyes furnished 
with distinct pigment and visual elements, and also 
by the different form of the frontal plate. 
Description of the female. 
The length of the body measured from the tip 
of the frontal plate to the extremity of the folded . 
caudal rami is, in the largest specimens that I 
have observed, taken off Lofoten, about 12 mm. 
Specimens from the south and west coasts of Norway 
are generally somewhat smaller. 
The form of the body (see Pl. I fig. 1 and 2) 
must be said to be, on the whole, rather slender, 
especially when the animal is observed in the liy- 
ing state. In specimens preserved in alcohol, the 
body appears, in general, to be somewhat shorter 
and stouter, owing to an appreciable contraction of 
the articulations between the various segments, pro- 
duced by the influence of the alcohol, a circumstance 
also noticed in the illustrations of this animal sup- 
plied by most other naturalists. The entire fore- 
most half of the animal is covered more or less 
completely by the carapace, behind which the grad- 
ually backwards-diminishing and very mobile tail 
projects freely. The habitual resemblance to a 
Copepod (especially certain Harpacticids) is unmis- 
takeable and becomes still more conspicuous when ~ 
we observe the animal in the living state, as the 
movements occur in an exactly similar manner. 
The carapace is very strongly compressed from 
the sides, so that its breadth but little exceeds half 
the height, and, besides, as it completely encloses 
between its lateral parts not only the oral parts 
but also all the succeeding appendages of the anterior 
division of the body (the branchial legs), it has 
more of resemblance to a bivalve shell, such as we 
find it in certain Phyllopods and Cladoceres. Also 
in other respects is this resemblance distinctly pro- 
minent. We may thus observe that this carapace 
forms, only within a very limited space quite in 
front and above, the immediate wall of the body 
(see Pl. If fig. 1), whilst it, otherwise, only quite 
loosely covers the body, which can therefore move 
itself freely within it. Finally, the 2 lateral parts 
or valves can, as in the above-mentioned Branchio- 
pods, be moved towards each other with the aid of 
a powerful transversal adductor muscle (see Pl. IL 
fig. 7, ms.) which immediately behind the oral parts 
connects the 2 valves to each other. The insertion 
of this adductor muscle may also be very distinctly 
observed from the exterior, in the foremost part 
of each valve next the dorsal side, in the form of 
