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Cladoscenium limbatum Jųrgensen, 1905

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Cladoscenium limbatum:
Resemble to some extent the foregoing species [Cladoscenium tricolpium], and is, on the whole, of the same structure, but, is nevertheless, quite different through the following special characteristics: The main spines are more broadly three-edged, each edge having 2 to 4 diverging spines, which nearest to the shell are often prolongated to arch-shaped fine, supporting branches, between the shell and the main spines. Such arches are only seen from the one or two innermost branches (spines) and most clearly on the upper side of the main spines. Outside the basal arches, perhaps only between the lateral spines, a brim-shaped continuation of the lattice shell is developed. This brim continues a little way forwards along the side of the main spines.

There is a verticil of branches high up on the columella, as in the foregoing species, but these branches are here almost straight on the distance between the columella and the shell.

The network of the lattice shell is much more perfect than in the foregoing species, most of the meshes being small and more or less distinctly square.

There is a trace of lattice wings from the top horn to the basal spines, and for this reason the species, perhaps, should most correctly be referred to the genus Pteroscenium HCK.

The cephalis is 52 µ in height, the width between the lateral spines 56 µ. The right, lateral spine is 68 µ in length outside the shell, the tophorn 50 µ. The stronger, primary arches seem here to become less conspicuous with growing age, so as to make the network more even in development. Finally the pores seem to disappear, being closed by thin plates, so that they are transformed into windows, not openings.

Only two specimens observed: 19/1 1899, 40 miles NW of Gaukvęrų, 0-700 m.
Jųrgensen 1905


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