99 



Gersemiopsis arctica, n. g. et n, sp. 



Tab. XIV. Tab. XA^, Fig. 1—13. 



Zoanthodemet er indtil 40"™ høit. Stammen er grenet 

 rund, temmelig haard, riflet efter Længden og omtrent 20™ m 

 i Omkreds ved Grunden, men smalner successivt af imod 

 Toppen, hvor den neppe er 5"™ i Omfang, og hvor den 

 ender med en større eller mindre Gruppe Polyper, Fig, 1, 

 Paa et Exemplar er Stammen rig paa Grene lige fra 

 Grunden og op til Toppen, Fig. 1; paa to andre er den 

 nederste Del af Stammen nøgen, saa at Grenene først be- 

 gynde omtrent 15 OTOT ovenfor Besaldelen, Fig. 2. Denne er 

 fast, membranagtigt udvidet og omfatter dels døde Koral- 

 stumper, dels Grus eller Smaastene. Grenene staa rundt 

 Stammen, temmelig langt fra hverandre og ere af forskjellig 

 Længde og Tykkelse; de længste ere fra 12 — 15 mm lange 

 og omtrent 2 mm brede ved Grunden, de ere runde, svagt 

 riflede og bære paa Enden en Gruppe Polyper ; de udsende 

 flere Smaagrene, der ere korte, tynde og ende hver i 3 — 6 

 Polyper, hvoraf dels 2, dels 3 ere sammenvoxede ved 

 Grunden,' Fig. 3, imedens ved Siden af disse hyppigt sees 

 en enkelt, isoleret Polyp, Fig. 3, a. Hos det ene Exemplar 

 iagttages paa de fleste Grene, næsten lige ved deres Ud- 

 spring, dels en enkelt Polyp, dels to, der forene sig ved 

 Grunden, for at gaa over i Grenen, ligesom der fra selve 

 Stammen udspringe dels enkelte, dels 2 eller 3 samlede 

 Polyper, Fig 1. Paa de to Exemplarer, hvor den nederste 

 Del af Stammen er nøgen, udspringe ingen Polyper direkte 

 fra dem 1 . Baade Stammen og Grenene ere rige paa Spikier. 



Polyperne ere cylindriske, men udvide sig noget mod 

 Tentakelskiven, Fig 4; de ere ikke retraktile, 8 — 9""" lange 

 med en udpræget Bagkrop, der er 4'"'" lang; Forkroppen er 

 2,5 mOT lang og Tentaklerne omtrent 3"™ lange. Paa Kroppen, 

 der er temmelig rig paa Spilder, ordne disse sig i 

 Længderækker, som fortsættes over paa Tentaklernes aborale 

 Flade, hvor de danne en tyk Kjøl, Fig. 4, imedens Side- 

 randene, ligesom Pinnulerne, ere uden Spilder, men derimod 

 besatte med Nematocyster, der ogsaa tindes paa den noget 

 hvælvede Mundskive. Munden er aflang med tykke Læber. 



1 Der findes næsten hos hver Art denne Slags Variationer og 

 ofte endnu større, som i de fleste Tilfælde gjør det vanskeligt, for 

 ikke at sige umuligt, alene efter Zoanthodemets Ydre at kunne be- 

 stemme Arten. 



Gersemiopsis arctica, n. g. et n. sp. 



Pl. XIV. Pl. XV, figs. 1—13. 



The Zoanthodem measures up to 40 wm in height. 

 The stem is ramous, cylindrical, pretty hard, grooved longi- 

 tudinally, and measures about 2Q mm in circumference at 

 the base, but diminishes, gradually, in thickness towards 

 the summit, at which point it measures, barely, o mm in cir- 

 cumference, and terminates in a larger or smaller group of 

 polyps (PL XIV, fig. 1). In one specimen the stem is rich 

 in branches, quite from the base and up to its summit 

 (PI. XIV, fig. 1). In two other specimens the inferior part 

 of the stem is bare, and the branches appear, first, about 

 15™ m above the basal part (PL XIV, fig. 2). This part is 

 hard and membranaceously dilated, and it includes, partly, 

 moribund coral lumps, partly, coarse sand or gravel. The 

 branches are placed around the stem, pretty far apart from 

 each other, and are of variable length and thickness; the 

 longest ones measure from 12 — 15 mm in length, and about 

 2 mn in thickness at the base. They are cylindrical, faintly 

 grooved, and carry on the extremity a group of polyps. 

 They send out several branchlets, which are short, and slender ; 

 each of these, again, terminates in 3 — 6 polyps, of which, 

 sometimes 2, and sometimes 3, are concreted together at 

 the base (PL XIV, fig. 3); whilst, at the side of these, there 

 is frequently seen a single isolated polyp (PL XIV, 

 fig. 3, a). In the one specimen there is observed, upon 

 most of the branches, almost quite at their root, sometimes 

 a single polyp, sometimes two which unite together at the 

 base in order to become produced into the branch, whilst, 

 also, their spring from the branch itself, sometimes a few, 

 sometimes 2 or 3 polyps placed together (PL XIV, fig. 1). 

 In the two specimens, where the inferior part of the stem 

 is bare, no polyps spring direct from it 1 . Both the stem 

 and the branches are rich in spicules. 



The polyps are cylindrical, but become somewhat 

 dilated towards the tentacular disk (PL XIV, fig. 4). They 

 are non-retractile, and measure 8 — 9 mm in length; they have 

 a well marked posterior body measuring 4" iB! in length, and 

 an anterior body measuring 2.5 mm in length. The tentacles 

 are about 3 fflm in length. Upon the body, which is pretty 

 rich in spicules, the spicules are arranged in longitudinal 

 series continued over into the aboral surface of the tentacles, 

 where they form a thick ridge (PL XIV, fig. 4), whilst the 

 lateral margins, as also the pinnules, are devoid of spicules 

 but, on the other hand, are beset with nematocysts, which 

 also are observed upon the somewhat arcuate oral disk. 

 The oral aperture is oblong, and has thick labiæ. 



1 There are found in almost every species variations of this 

 nature, and frequently still greater variations, which, in most cases, 

 makes it difficult, if not impossible, to determine the species from 

 the exterior of the Zoanthodem alone. 



