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Euscenarium joergenseni
(Dumitrica, 1978)
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Description - Add description
Cladoscenium tricolpium
Here again we have the four primary spines and the ventral sagittal one. The almost central columella corresponds to the basal, dorsal spine, D, in Plectacantha oikiskos and Phormacantha hystrix. On the other hand, the connection with Protoscenium simplex is evident.
From two, somewhat upwards pointing, branches from each of the left and right lateral spine four arches extend upwards and unite in twos (those from the same main spine) to form a strong apical arch. These are the corresponding arches in Protoscenium simplex, where they connect the branches of the lateral spines with the corresponding two branches of the apical one (D). The tips of these branches have disappeared in Cladoscenium, and the arches pass gradually into the branches. The two corresponding ones in the dorsal spine (A) are also found; but one of them is not particularly conspicuous as there are several similar secondary arches.
The lattice shell (cf. Jörgensen 1. c. p. 78) is particularly perfect between the apical spine (D) and the ventral, sagittal one.
There are, where the main spines protrude, rather large, triangular meshes formed by connecting beams between the larger arches of the shell and the spines, two at the dorsal spine (A) and the left, lateral spine (Lr), three at the apical spine (D). It is only in older individuals that the long, line downhanging spines are formed on the basal arches (i. e. the arches between the basal spines. A,Lr and Ll).
There does not seem to be anything of importance to prevent us from considering this species to be identical to Euscenium tricolpium Hck. It is true that, in Haeckel's illustration, the distinct, ventral, sagittal spine is not present. There are, however, so many details in the illustration, which answer remarkably well to this species that it is highly probable that they are identical. The reason why Haeckel refers the species to the genus Euscenium, is that he considers the shell to be closed by the strong apical arches, (which are conspicuous in certain sightings of the microscope) while it really extends farther up along the apical spine, to the three connecting beams above mentioned.
My opinion therefore is still that the species is a Cladoscenium. Haeckel mentions the completely corresponding upper arches in Cladoscenium pectinatum Hck. (L. 86, p. 1150, pl. 98, f. 2), as a second verticil of branches of the columella.
Frequent, always in small numbers, in deep water, up to 100 m.
Distribution: Not rare on the west coast of Norway, here too sparse, and only in deep water samples. Was found in surface samples from the warmer and salter Atlantic waters V2 1901, in the sea beyond Søndmøre, 13/2 off" Lofoten and 5/3 off Finmarken (cfr. Gran L. 70, pp. 150, 151, 154). Mentioned by Haeckel from a great depth in the Central Pacific. Cleve has found the species at a great depth west of Spitzbergen and at some places in the northern and north western parts of the Atlantic. Cleve (L. 40, p. 161) remarks that the species, though often found together with Styliplankton (temperate oceanic), does not, however, appear to be a Styliplankton form. Cleve considers it likely, either that it comes from the northern polar basin, or from the Northern Pacific. Cfr. above, p. 128.
| | Jørgensen 1905 | Clathromitra joergenseni
Petrushevskaya (1971, p.76) has remarked that C.tricolpium described by Jörgensen does not belong to Haeckel species. In agreement with this we propose a new name for Jörgensen's species. Its representatives in the Radiolarian Shales are very rare.
| | Dumitrica 1978 | Eucenarium joergenseni (sic)
The thoracic length and ornamentations are variable among the examined specimens. This species represents one of the most characteristic radiolarians from the Toyohama Formation, Morozaki Group (listed as Euscenium sp. aff E. tricolpium in Table 1 of Sugiyama, 1992). Against the fact its occurrence in the Oidawara Formation is extremely rare.
| | Sugiyama and Furutani 1992 |
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