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Drymyomma elegans Jørgensen, 1900

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Drymyomma elegans:
Aeussere Kugel dickwandig, mit ziemlich grossen, breitwandigen Poren, Durchmesser 0,096 mm.

Mittlere Kugel mit viel kleineren, breitwandigen Poren. Durchmesser 0,036 mm.

Innerste Kugel ungefähr wie die zweite, nur kleiner: Durchmesser 0,015 mm.

Ungefähr 20 kräftige, dreischneidige, lang zugespitzte, im Basaltheile breite Hauptstacheln, die etwas ungleich lang sind, bis 0,084 mm. hervorragend. Diese Hauptstacheln sind zwischen den zwei äusseren Kugeln schmäler, erreichen ihre grösste Breite erst an der Aussenseite der dritten Kugel. Die kleinsten Radialstacheln sind häufig mit einem einfachen Ast versehen.

Ausserdem finden sich an der äusseren Kugel zahlreiche cylindrischen Nebenstacheln, etwas mehr als halb so lang wie die Hauptstacheln, an der Mitte oder höher in 2 bis 4 divergirende Aeste getheilt.

Diese schöne neue Art ist bei uns selten: Mai, August-Novbr., immer sehr spärlich.

Ich habe nur wenige Male die ganz entwickelte Form mit den characteristischen verzweigten Nebenstacheln gefunden. Häufig kommt eine andere vor, die sehr an Echinomma trinacrium erinnert, jedoch viel schlankere Haupt- unt Nebenstacheln besitzt. Die letzteren sind an solchen Exemplaren viel weniger entwickelt, ausserdem noch unverästelt.

Diese Formen lassen sich meiner Erfahrung nach ungezwungen als eine Jugendform der obigen Art erklären.
Jørgensen 1900
Drymyomma elegans:
This species, when fully developed, is very easily recognized by its branched byspines on the outside shell.

The outside shell is strongly developed, thick walled, diameter ± 85µ. The pores are roundish with broad intermediate walls, unevenly developed, though not so much so as in Chromyechinus borealis, on an average about the same size or perhaps most of them little smaller.

The two inner shells seem in all important respects to answer to those of the following species, Chromyechinus borealis. Still, I must call attention to the fact that I have had very little chance of examining them more thoroughly, as the species occurs so sparsely.

The number of the main spines seems to vary (?) from about 15 up to about 20. The largest are beautifully developed, long, slender and always branchless, a few of the smaller ones seem, on the contrary, occasionally to have a single needle shaped side branch, like the corresponding one in Chromyechinus borealis.

Of byspines there are some resembling the main spines, only smaller and especially narrower. From these 3-edged spines there seems to be every transition to numerous narrow needle shaped ones without distinct edges.

Most of the byspines, especially the narrow ones, carry in their upper halves from 1-4 obliquely diverging narrow branches, some of these again carrying a similar, but shorter, side branch.

There seems to be a regular transition from the more delicate radial spines to the more strongly developed, 3-edged and branchless, byspines.

It is, however, as above mentioned, probably not quite certain that the previously mentioned Echinomma-forms with long, slender main spines and byspines, should all be included in this species. These forms occur, with us, much more frequently than the fully developed Drymyomma elegans.

Rare and scarce, only found at a few places in 1899: Sea off Gaukværö, 19/1, 0-700 m., Senja, 21/1, 0-130 m., the Vest Fiord, 1/2, 0-200 m., Skorven, 4/2, 350-300 m., the Tys Fiord I, 28/3, 0-700 m.

Distribution: Very rare also on the west coast of Norway, only in deep water. Also known from the Norwegian Ocean off Sundmøre and from the Vest Fiord, Feb. 1901 (Cfr. Gran L. 70, p. 150-151).
Jørgensen 1905


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