Hudskelet af Stichaster albulus og Fig. 16, Tab VI, et 
lignende af Stichaster roseus. 
Hudskelettet hos Slegten Asterias dannes, som tidli- 
gere berort, af storre og mindre Kalkstykker, der ogsaa 
kan siges at vere taglagte, rigtignok paa en anden Maade, 
idet de. korte, smale Kalkstykker legge sig med deres af- 
stumpede Ender paa hverandre og danne længere Tver- 
bjelker, der ved at støde til de store, regelmæssigt formede 
og i Længderækker taglagte Kalkplader danne store Masker, 
hvori flere Tentakelrør optages, se Fig. 10, Tab. IV. 
Sammenligner man Ryggens Hudskelet hos Asterias 
rubens med det hos Stichaster roseus, saa vil man finde, 
at Kalkstykkerne ere tildels forskjellige i Form; men væ- 
sentligst forskjellige ere de 1 deres Anordning. Hos Aste- 
rias rubens danne de meget vide Masker, der optage flere 
Tentakelrør, imedens de hos Stichaster ere meget tæt tag- 
lagte, hvorved Maskerne blive yderst smaa og give Plads 
kun for 1, hoist 2 Tentakelrør. Hos Asterias rubens bæ- 
rer hver Kalkplade paa Rygsiden 1 Regelen kun 1 Pig; 
hos Stichaster roseus er der flere Pigge. 
Efter dette skulde man tro, at Slegten Stichaster var 
forsaavidt vel begrundet, som man vil lade Hudskelettet 
vere afgjorende for en Slægts Dannelse. Men nu kommer 
Overgangsformerne, hvortil vi maa henregne Asterzas spits- 
bergensis og hyperborea samt Asteracanthion albulus, og da 
udfyldes Kloften mellem Slægterne Asterias og Stichaster 
temmelig betydeligt, saa at der opstaar Tvivl om, til hvil- 
ken Slægt de nævnte Arter skulle henføres. 
Asterias stellionura, Edm. Perrier. 
Tab. IV, Fig. 19. 
Asteracanthion stellionura, Valence. Coll. Mus. manuserit. 
1869. Asteracanthion stellionura, Ed. Perrier. Recherches 
sur les Pédicellaires, pag. 240, pl. 17, fig. 10, a, 
b, c, d. Annales des sciences naturelles 5° Sér. 
Tome XII. 
1875. Asterias stellionura, Ed. Perrier. Archives de Zoo- 
logie expérimentale et générale. Tome 4, pag. 310. 
1878. Asterias stellionura, Verrill. Marine Fauna of North 
America, American Journal of Science and Arts, 
3™ Series, Vol. XVI, pag. 214. 
Søstjernens Diameter 260". Skiven er liden, omtrent 
30”” 1 Gjennemsnit, kun lidet hvælvet. De 5 Arme ere 
fra 110—120"" i Længde, temmelig flade; 18”” ved Grun- 
14 
Pl. VIII, fig. 15, dermal skeleton of Stichaster albulns and 
Pl. VIII, fig. 16, dermal skeleton of Stichaster roseus, will 
serve for comparison. 
The dermal skeleton in the genus Asterias is formed, 
as previously stated, of larger and smaller calcareous os- 
sicles, which may also be said to be imbricate, although in 
another manner, in as much as, that the short narrow cal- 
careous ossicles lie on each other with their truncated ex- 
tremities, and form longer transverse ribs, which by unit- 
ing with the large, imbricate calcareous plates arranged 
in regular longitudinal series, produce large meshes, in which 
several tentacular tubes are visible, vide Pl. TV, fig. 10. 
If we compare the abactinal dermal skeleton in Aste- 
vias rubens with that of Stichaster roseus, we find that the 
calcareous ossicles differ, partially, m form, but still more 
particularly, im arrangement. In Asterias rubens, they form 
very wide meshes which include several tentacular tubes, 
whilst in Stichaster, they are very closely imbricate, pro- 
duce extremely small meshes, providing space for 1, or at 
most 2 tentacular tubes. In Asterzas rubens, each calear- 
eous plate carries, as a rule, only I spine on its dorsal 
surface, whilst in Stichaster roseus, it carries several spines. 
From this we may gather that the genus Stichaster, 
was, in so far, well substantiated, if we assume the der- 
mal skeleton to be the decisive feature in the formation 
of a genus. But, now come the transition-forms, to which 
we must assign Asterzas spitsbergensis and Asterias hyper- 
borea, as well as Asteracanthion albulus, and then the gap 
between the genera Asterias and Stichaster is so much 
reduced, that there arises a doubt as to which genus, the 
species named ought to be assigned. 
Asterias stellionura, Edm. Perrier. 
PI. IV, fig. 1—9. 
Astcracanthion stellionura, Valence. Coll. Mus. manuscrit. 
1869. Asteracanthion stellionura, Ed. Perrier. Recherches 
sur les Pédicellaires, pag. 420, Pl. 17, fig. 10, a, 
b, c. d. Annales des sciences naturelles 5° NSér. 
Tome XII. 
1875. Asterias stellionura. Ed. Perrier. Archives de Zoo- 
logie, expérimentale et générale. Tome 4, pag. 310. 
1878. Asterias stellionura. Verrill. Marine Fauna of 
North America, American Journal of Science and 
Arts 3" Series, Vol. XVI, pag. 214. 
The diameter of this starfish is 260". The disk is 
but small, being only about 30”” in diameter, and it is 
only slightly convex. The tive rays are rather flat; they 
