O trylobicie Acastella prima n. sp.

Ewa Tomczykowa

Abstract


NOTES ON TRILOBITE ACASTELLA PRIMA N. SP.

This paper deals with the description of a new species of trilobite, Acastella prima n. sp. which was found in the Lębork bore-hole (Pomerania) in the Upper SiIurian, at the top of the Siedlce beds in the zone Monograptus formosus. This is a form standing at the boundary of two genera, i.e. of Acaste and Acastella. The author presents a description of this form, adding an analysis correlating it with species most closely resembling this new form.

Acastella prima n.sp.

D i a g nos i s: Glabella wide in front, rounded. Axial furrow diverted outwards from axis at an angle of some 20°. S1 and S2 short and almost parallel with the occipital furrow, S3 at front bent backwards, at the height of the front end of the eye connected with axial furrow. Palpebral lobe slightly inclined towards axial furrow. Genal angle with a nodule directed rearwards, corresponding to genal spine in younger Acastella forms.

The thorax consists of 11 segments, the rhachis equals almost 1/4 of the total width; the pleurae are terminated by a distinct small nodule. The pygidium is triangular; its posterior border is pointed.


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