53 



Basaldel er ganske smal og Endedelen sammensat af 12 

 med lange Svømmebørster forsynede Led. 



Bagkropslemmerne er af den for Hunncrne af denne 

 Familie sædvanlige rudimentære Beskaffenhed, kun dannende 

 lancetformige, med fint cilierede Borster besatte ubevæge- 

 lige Plader. 



Det midterste Halevedbæng (Pl. V. Fig. 20) er af 

 et meget eiendommeligt Udseende og uligt samme hos de 

 øvrige bekjendte Mysider. Det er ganske kurt. pladeformigt 

 ng næsten qvadratiskt. kun ubetydeligt afsmalnende mod 

 Enden, der i Midten er dybt indskaaret. Indsnittet. der 

 omtrent indtager i j i af Vedlnengets Længde, er vinkelformigt, 

 med Kanterne næsten lige, stærkt divergerende og i bele 

 sin Længde fint saugtakkede. Paa Spidsen af enhver af de 

 triangulære Endefiiger staar en enkelt Torn og foran denne 

 er til Sidekanterne fæstet en Rad af 8 — 12 meget smaa 

 Torner, der dog kun naar omtrent til Midten af Vedhængets 

 Længde. 



De ydre Halevedbæng (Fig. 21) har Endepladerne 

 temmelig store, af lancetdannet Form og rundt om besatte 

 med de sædvanlige Randbørster. Den indre Plade er noget 

 kortere og smalere end den ydre og viser ved Basis kun 

 en yderlig svag Antydning til det sædvanligt ber forekom- 

 mende Horeapparat. Dens indre Kant er under Rancl- 

 børsterne næsten i sin bele Længde forsynet med en Rad 

 a f korte Torner. 



Paa det under vor Expedition erholdte Individ var 

 bele Legemet gjennemsigtigt. af hvidagtig Farve og uden 

 det mindste Spor af nogen Pigmentering. 



Længden af det største af de to foreliggende Exem- 

 plarer synes at have været omkring 35"""; men det var 

 endnu ikke forsynet med tydeligt udviklede Æggeplader og 

 kan derfor heller ikke autages at have naaet sin fulde 

 Størrelse. 



Forekomst og Udbredning. Af denne mærkelige 

 Mv side blev et enkelt Exemplar under Expeditionens sidste 

 Togt optaget ved Hjælp af Trawlnettet fra det enorme Dyb 

 af UIO Favne i Havet NV af Finmarken (Stat. 295). Det 

 andet mindre Exemplar blev. som ovenfor anført, fundet af 

 R. Collett i Ventrikelen af Rhodichthys regina, der op- 

 toges paa den længere vestlig beliggende Stat. 297 fra et 

 endnu større Dyb. nemlig 1280 Favne. Ogsaa dette Ex- 

 emplar var selvfolgeligt incomplet, men viste dog de for- 

 skjellige Kropsvedhamg bedre vedligeboldte end bos det andet. 



At denne Myside er en i ganske særlig Grad udpræget 

 Dybvandsform. fremgaar ikke blot af Findestederne, men 

 ogsaa af flere Punkter i dens Organisation, navnlig de fuld- 

 kommen rudimentære Øine, de tynde Integumenter og Mangelen 

 af Pigmentering. Da begge Stationer tilhorer den kolde Area. 

 maa den desuden antages for at være en ægte arktisk Form, 

 der rimeligvis er udbredt over hele det dybe Havbasin i 

 Nordhavet. 



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 (Pl. V, fig. 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 ajtpendages (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 3o'" m ; but as 

 vet the animal was not furnished with distinctly developed 

 incubatory plates, and can hardly therefore have attained 

 its full size. 



Occurrenee and Distribution. - Of this remarkable 

 Mysidian, a single specimen was tåken, in the trawl. on 

 the last cruise of the Expedition, at the enormous depth 

 of 1110 fatboms, 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 bad the various 

 appendages to the body in a better state thau 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. 



