Opisthoporus penangensis Stoliczka, 1872
“This species is evidently closely allied to E. v. Martens’ O. sumatranus, which is of nearly exactly the same size, but its whorls are decidely thinner and on the upper side more flattened, the upper apertural margins are considerably more produced, the plain of the aperture being, therefore, more oblique to the axis, while the sutural tube appears to be more distant from the margin. The direction of the tube was observed in four specimens of O. sumatranus to be nearly vertical, while in about eighty specimens of the Penang form it is directed backwards, being sometimes when well preserved perfectly parallel to the suture; in a few specimens, however, it is nearly vertical, and in two or three even slightly directed forward. The character is, therefore, evidently variable. Young shells, sometimes measuring up to 9 mm in the longer diameter, still have ni sutural tube developed, while others (mostly males) reach the adult stage already at even a somewhat smaller size.” (Stoliczka, 1872)
Stoliczka (1872) original descriptions on Opisthophorus penangensis – “O. testa sub-discoidea, apice paulum exserta, latiuscule umbilicata, corneo solidula; anfractibus 4.5 ad 5, teretibus, sutura profunda junctis, epidermide brunnea vel nigrescente, transversim confertissime striata, in ultimo anfractu ad peripheriam superam et inferam breviter ciliata, indutis, sub epidermidem albescentibus atque strigis transversis, brunneis vel fuscis, paulo undulatis, aut plus minusve acute angulatis, notatis; apice sub-mammillato, nigrescente vel pallido; umbilico modico, fere dimidium latitudinis anfractus penultimi exponente; ultimo anfractu ad aperturam valde descendente, sed haud dissoluto, ad suturam tubulo brevi tenuique, saepissime retrorsum curvato, rare fere verticali, rarissimeque antice versus directo, in speciminibus adultis circa 1.5 ad 2 mm a margine aperturali distante, instructo; apertura circulari, ampla, obliqua, peristomate in junioribus simplici, in adultis breviter bilabiato, margine labii interni paululum incrassato, saepe rubescente tincto, haud distincter discreto, externo expansiusculo; ambobus supra paulum productis atque prope suturam modice insinuatis. Operculum discoideum, interne vix, externe distincte, concavum et album, multispiratum, medio corneo-testaceum, laminis duabus separatis ad peripheriam acutissimis.”
Kobelt (1902) descriptions on Cyclotus (Siphonocyclus) penangensis – “Schale ziemlich weit genabelt, fast scheibenförmig, ziemlich festwandig, weisslich mit braunen welligen Striemen; Periostracum dicht gestreift, schwarzbraun, über und unter der Mitte beliaart; Apex fast zitzenförmig ; 4½-5 stielrunde Windungen, letzte vorn sehr herabsteigend, nicht abgelöst, mit einer kurzen, gekrümmten, meist rückwärts, seltener senkrecht oder vorwärts gerichteten Nahtröhre, l½-2 mm hinter dem Mundraude; Mündung weit, schräg, kreisrund; Mundrand doppelt: innerer wenig verdickt, oft rötlich, äusserer leicht ausgebreitet, beide oben vorgezogen und leicht ausgebuchtet. Deckel innen kaum, aussen deutlich konkav, weiss, mit vielen Windungen, mit 2 am Rande sehr scharfen Platten.”
“Animal stout, blackish, sometimes mottle with grey and tinged with pink, nearly smooth, with few little warts, paler at the sides and at the end of the foot which is, when fully extentedm about twice the longer diameter of the shell; it is pointed at the end; operculigerous lobe slightly more thickened in front than behind; tentacles paler at base, blackish on terminal half, slightly thickened towards the end, but pointed terminally; eyes small, on laterally slightly prominent bulgings, united to the base of the tentacles; rostrum wrinkled, cleft in front, and with pale lips; penis of male long, thin and black, without any appendage.” (Stoliczka, 1872)
Opisthophorus penangensis – “Diam. Maj. 11.5; diam. Min. 9.5; altit. Testae 6.6; diam. Apert. Int. 4, externae cum perist. 4.7 mm.” (Stoliczka, 1872); Cyclotus (Siphonocyclus) penangensis – “H. 6.6, Durchm. 1l.5:9.5mm.” (Kobelt, 1902)
Type locality – “Penang” (Stoliczka, 1872)
Other localities – “royaume de Pérak, dans celui de Patani; dans la province Wellesley et à Poulo Pinang” (Morgan, 1885)
“…the species common under dead leaves on the ground along the base of the Penang hill, mostly in dense jungle.” (Stoliczka, 1872)