Tracheleuglypha miocenica  Frenguelli, 1932
Basionym: Tracheleuglypha dentata var. miocenica Frengelli, 1932

Diagnosis: Elongated ovoid shell with regular outlines, sometimes slightly swollen on one side near the oral pole; length 57–63 μm, width (maximum diameter) 28–33 μm. It is composed of hyaline plates, slightly oval or completely round, regularly imbricated but with uneven surfaces, so that irregular hexagonal areas remain visible between the overlapping surfaces. Over the entire surface of the shell body the plates are almost identical in both shape and size, with diameters generally ranging between 9.5 and 10.5 μm (smaller axis) and 10 to 11.5 μm (larger axis). Even those at the posterior pole, always with regular curvature, although often somewhat crowded, retain the same shape and size as those on the body; only exceptionally do one or two slightly smaller plates appear.

At the oral pole, however, in shells where it is preserved intact, two perioral series of smaller plates can be observed, whose diameters are around 5 μm. Sometimes these are reduced to a single marginal series; but in that case, between this and the first series of body plates, there is often a series of plates of intermediate size. Around the mouth, always circular in section, the shells often preserve a short collar (almost always reduced to wrinkled, difficult‑to‑see fragments) composed of thin, delicate hyaline silica with a toothed margin. The denticulations are generally blunt, irregular in shape, and variable in number and size; but in one case they consisted of six large pointed triangular teeth, separated by wide notches extending the full height of the collar. The diameter of the oral aperture (excluding the collar) varies from 10 to 12 μm.

This new variety coincides, in most of its characters, with the type as described and illustrated by Leidy (1879), Penard (1902), and Deflandre (1928). But it differs above all in the structure of the perioral region: the series or double series of smaller plates, which is not found in any shell of the forms described so far, undoubtedly constitutes a characteristic of unquestionable morphological value and might even justify the creation of a separate species. Another important character is the silicification of the perioral collar which, in the type, according to Penard, is completely destroyed by sulfuric acid; whereas in the shells I observed, the collar has often resisted not only time but also repeated strong attacks of acids and alkali. Finally, as additional differential characters, one could add: plates and shells somewhat larger than those indicated by the various authors.

Compared with var. elongata Playfair (1917), it coincides with it in the shape of the shell and in the various morphological details of the body and collar; but it differs in the larger size of both shell and plates. As for the structure of the perioral region, in Playfair’s fig. 2 one seems to discern a series of smaller plates similar to those in my variety; but in the text the author says nothing about this.

Dimensions: Length 57–63 µm; width 28–33 µm.

Ecology: Fossil.

Remarks: This species was described from fossil material. The complete description, translated from Italian into English, was made by Copilot.