70 



ere meget talrigere, større og stillede i 4 lige Længdera- 

 der og i Tværretning dannende skraa Rader, bemærkes 

 en ForsJcjel i AmbulacralsTcelettet mellem denne og de 2 

 andre Arter af Slægten. Hos de sidste (se Fig. 18, 21, c) 

 ere Hullerne eller Løkkerne mellem Ambulacralhvirvlerne, 

 hvoraf Sugefødderne komme frem, ovale (i Tværretning) 

 og danne i hver Straale 2 ganske lige parallele Længde- 

 rader. Hos P. multipes ere derimod disse Løkker (Fig. 

 14, 15, 16, c, d) betydeligt større og langstrakt parabo- 

 liske (ligeledes, i Tværretning) eller omtrent dobbelt saa 

 brede som hos P. pulvillus (hvilken større Brede allerede 

 hentyder paa den betydeligere Størrelse af de i dem an- 

 bragte Sugefødder) og danne 2 svagt bøiede longitudinale 

 Zigzaglinier i hver Straale, idet de i hver Rad ere af- 

 vexlende bredere og hver anden af dem (d) saaledes naar 

 noget længere ud paa den ydre Side af Straalen end den 

 foregaaende og efterfølgende (c). Hos Slægten Asterias, 

 hvor jeg har undersøgt dette Forhold hos A. rubens og 

 A. glacialis, danne disse Løkker (Fig. 22, 23, c c), hvilke 

 her ere ligestore og ovale ligesom hos vore 2 andre 

 Pterasterarter, altsaa meget mindre langstrakte end hos 

 P. multipes, 2 meget stærkt bøiede Zigzaglinier eller ret- 

 tere 4 lige Linier, idet de 2 Rader paa hver Side regel- 

 mæssigt afvexle med hinanden. Forholdet i denne Hen- 

 seende hos nærværende Søstjerne staar netop midt imel* 

 lem eller danner Overgangen fra det hos de 2 andre 

 Pterasterarter og de talrige øvrige Søstjerneslægter med 

 kun 2 Rader Sugefødder til det hos Asterias (idetmindste 

 de europæiske Arter af denne Slægt) der har 4 Rader 

 saadanne, stedfindende Forhold. 



En Eiendommelighed ved denne saavelsom begge de 

 andre norske Arter, altsaa udentvivl characteristisk for 

 Slægten, er det, at den indre Endedel af begge Ambula- 

 cralhvirvler (Fig. 16, 17, h), med hvilken de formedelst 

 smaa Tænder, der besætte dens brede afkuttede indre 

 eller imod hinanden vendte Endeflade (Fig. 17, i), artiku- 

 lere med hinanden, er stærkere tilbagebøiet (i Retningen 

 indad imod Munden og under en stump Vinkel) end hos 

 nogen anden mig bekjendt Søstjerneslægt. 



Forekomsten af 4 Rader Sugefødder hos en Ptera- 

 ster, en Slægt der staar midt inde iblandt den store Fa- 

 milie af Søstjerner, som af Müller og Troschel, der stille 

 Slægten nær ved Asteriscus, netop characteriseres ved 

 Besiddelsen af kun 2 Rader saadanne, var vistnok uven- 

 tet og overaskende, og mangen overfladisk Iagttager vilde 

 vel ikke betænke sig længe paa for vor Søstjerne at danne 

 en ny Slægt, maaske endog • en Familie. Jeg kan dog 

 ikke paa nogen Maade beslutte mig til at adskille den 

 fra de andre Arter af Pteraster, med hvilke den, som 

 man vil have seet, i sin hele øvrige Bygning paa det 

 nøieste stemmer overens, og jeg ser i det omhandlede 

 Forhold ingen fundamental Forskjel, ikke engang en ge- 

 nerisk, men kun en specifisk Forskjel. Aabenbart er det 

 den store Mængde Sugefødder, som hos denne Art skulde 

 anbringes i Straaler af ringe Længde, som har gjort en 

 Forandring i det hos de andre Arter i denne Henseende 

 stedfindende Forhold nødvendig, og ved en ringe Modifi- 



cies being much more numerous, larger and placed in 4 

 straight longitudinal rows, and forming oblique rows in 

 a transverse direction, a difference in the ambidacral skele- 

 ton is remarked between this and the 2 other species 

 of the genus. In the latter (see fig. 18, 21, c) the cavi- 

 ties or vacancies between the ambulacral vertebræ from 

 which the suction feet proceed, are oval (in the transverse 

 direction) and form in each ray 2 quite straight parallel 

 longitudinal rows. In P. multipes these intervals (fig. 14 

 15, 16, c, d) are considerably larger and of an elongated 

 parabolic form (likewise in the transverse direction) or 

 about twice as wide as in P. pulvillus (which greater 

 breadth already indicates the more considerable size of 

 the water-feet located there) and form 2 slightly curved 

 longitudinal zigzag-lines in each ray, being in each row 

 alternately broader; and every alternate one of them (d) 

 extends therefore rather more on the outer side of the 

 ray than the preceding and following one (c). In the 

 genus Asterias where I have examined this point in A. 

 rubens and A. glacialis, these spaces (fig. 22, 23. c c), 

 which here are of equal size and oval, as in our 2 other 

 species of Pteraster — that is much less elongated than 

 in P. multipes-form 2 very strongly curved zig-zag lines 

 or more properly 4 straight lines; the 2 rows on each 

 side alternating regularly with each other. In this par- 

 ticular our present star-fish stands just midway, or forms 

 the transition between the 2 other species of Pteraster 

 with the numerous other genera of star-fish that have 

 only 2 rows of water-feet, and the Asterias (at least the 

 European species of this genus) which have 4 rows. 



A peculiarity in this as well as in both the 2 other 

 Norwegian species, and thus without doubt characteristic 

 of the genus is that the interior extremity of both am- 

 bulacral plates (fig. 16, 17. h) 'with which they are arti- 

 culated together by means of small teeth covering their 

 broad truncated interior or contiguous terminal surfaces, 

 (fig. 17, i)„ are more strongly recurved (inwards towards 

 the mouth and at an obtuse angle) than in any other 

 genus of star-fish known to me. 



The occurrence of 4 rows of water-feet in a Pteraster, 

 a genus standing in the midst of the great family of star- 

 fish which according to Müller & Troschel, who place the 

 genus near to Asteriscus, is precisely characterised by 

 possessing only 2 such rows, was certainly unexpected 

 and surprising; and many a superficial observer would 

 certainly not hesitate long in establishing a new genus 

 for our star-fish, perhaps even a new family. I can 

 however by no means persuade myself to separate it 

 from the other species of Pteraster with which, as is 

 evident, it otherwise agrees most minutely in its whole 

 structure; and I do not see in the particular case under 

 consideration any fundamental difference, nor even a ge- 

 neric, but only a specific difference. It is clearly the great 

 number of water-feet which in this species have to be 

 located in rays of little length, that has rendered neces- 

 sary an alteration of the arrangements observable in other 

 species; and by a slight modification of the ambulacral 



