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Plectacantha trichoides Jørgensen, 1905

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Plectacantha trichoides:
I have only in imperfect knowledge of this species, as I have only seen a few specimens, and at first took these to belong to the preceding species (Plectacantha oikiskos).

It has the same primary spines and primary arches; but there appears to be the important difference that the ventral, primary arch and the left, lateral arch both extend to the left, lateral spine, not to a common basal branch from the latter. On the other hand, there is a strong, secondary arch between the left, lateral one and the nearest side of the primary, ventral one.

In outer appearance, this species is very different from the foregoing one. Instead of the numerous secondary meshes, long connecting arches are developed, which form together a longish, ovate, very imperfect network of long, fine arches. The largest and strongest of these ran between the two lateral arches and form a very large, ovate mesh, pointing downwards. On its sides, especially in a ventral direction, similar large meshes are, developed, bounded by fine arch branches, which run from the primary arches to the said large, secondary one, or between secondary arches. On these arch branches, very fine spines are scattered, these probably later on being, developed into arch branches between the secondary arches. It is likely that a network will appear which is imperfectly closed beneath by basal, secondary arches, on elder individuals.

On the primary, basal spines, short byspines are also found on the pieces inside the primary arches.

This species is undoubtedly different from the foregoing. It is not certain whether it should be reckoned as belonging to the same genus; but it wants, as does the foregoing one, the ventral, sagittal spine.

Very rare and scarce, though certainly to some extent overlooked: 19/1 1899, 40 miles NW of Gaukværø, 0-700 m.

Distribution: Also on the west coast of Norway, but only occasionally and in small numbers.
Jørgensen 1905


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