Plekocheilus (Eurytus) tepuiensis, Breure, Abraham S. H., 2009

Breure, Abraham S. H., 2009, New Orthalicidae (Mollusca, Gastropoda) from Venezuelan Guayana: unravelling secrets from the Lost World, Zootaxa 2065, pp. 25-50 : 36-37

Plekocheilus (Eurytus) tepuiensis spec.nov.

( Figs 6 H─J, 9J)

Diagnosis. A species characterized by the obliquely descending zig-zag streaks; surface hardly shining, with spiral lines of dot-like granules on the last whorl.

Description. Shell 35 mm (further dimension given in Table 1 ), 1.7 times longer than wide, imperforate, ovate, sides hardly convex, rather thin. Colour pale yellowish brown, with descending, somewhat oblique stripes of reddish-brown, broken up into separate stripes of different length; upper whorls lighter, corneous, eroded. Surface hardly shining, upper whorls with growth striae, on the penultimate and ultimate whorls transferring into spiral lines of dot-like granulation, more oblong towards the aperture. Protoconch smooth (eroded). Whorls 4.5, rather flat, the last whorl somewhat swollen, suture somewhat impressed, hardly descending in front. Aperture ovate, somewhat skewed, the colour pattern from the outside shining through, 1.7 times longer than wide, 0.65 times the total length; peristome thin and hardly reflexed, whitish with a hue of pink. Columellar margin straight, entering the aperture with a weak fold, hardly dilated and somewhat receding. Parietal wall with a thin, translucent callus.

Type material. Venezuela, Estado Amazonas, Cerro Yapacana, 800 m, J. Cerda leg., 21.ii.1978. Holotype RMNH 112031.

Comparison with other taxa. Differs from P. (E.) huberi spec.nov. by (1) the less descending last whorl; (2) by the different granulation on the last whorl; (3) being less slender. It may also be compared to P. (E.) gibber , from which differs in (1) having the last whorl less descending in front; (2) having the suture less impressed; (3) the different shape of the aperture.

Remarks. Only a subadult specimen is known. The colouration and especially the sculpture of the last whorl (Fig. 24J) sets it apart, but it seems most closely allied to the species with which it is compared above.

Etymology. The name refers to the type locality, Cerro Yapacana, an isolated tepui.

Figures

FIGURE 6. Shells in Plekocheilus. A ─ C. P. (Eurytus) mundiperditi Haas, 1955, RMNH 112030. Photos J. Goud. D ─ G. P. (E.) ta t e i Haas, 1955. D ─ F. Paratype FMNH 50346. G. Holotype AMNH 73455. H ─ J. P. (E.) tepuiensis spec. nov., holotype RMNH 112031. Photos J. Goud. K. P. (Eudolichotis) sinuatus (Albers, 1854), RMNH 112032. Scale bar— 1 cm.