Oxychilus alliarius

Oxychilus alliarius (J. S. Miller, 1822) Fig. 5 Worldwide distribution. Originally described from the “ Environs of Bristol ”, England (Miller 1822). Its native distribution includes Iceland, Greenland (Roth and Sadeghian 2003), and Central and Western Europe (Horáčková and Juřičková 2009). It has been reported as introduced in Austria, Belgium, Denmark, Estonia, Finland, France, Germany, Great Britain, Greece, Czech Republic, Spain, and Portugal (Horáčková and Juřičková 2009; Borges et al. 2010; De Oliveira and Altonaga 2010; IUCN Red List 2017), and spread to Hawaii (Cowie 1997), Tasmania (Kershaw 1991), South Atlantic (Preece 2001), North America (Forsyth 2004), Colorado, the Pacific coast states (Roth and Sadeghian 2003), South America (Hausdorf 2002), Chile (Cádiz et al. 2013), Sri Lanka (Naggs et al. 2003), Madeira (Seddon 2008), and the Philippines (Tañan and Sumaya 2024). Distribution in Mexico. Puebla (Teopancingo), Transmexican Volcanic Belt Province. Diagnostic features. Two specimens were dissected. The proximal part of the penis is initially wider and then gradually becomes distally narrower as described by Giusti and Manganelli (2002) (Fig. 5 D, G). Internally the proximal (Fig. 5 E, H) and distal penis show 2–4, thin, slightly undulating, longitudinal folds that seem to be a continuation of one another, but never showing lateral branching or assuming a papilla-like shape (Fig. 5 F, I). Shell discoidal, depressed, slightly convex above, compressed below, thin, semitransparent, variably shiny, yellowish to yellowish-brown, opalescent below (Fig. 5 B, C); surface fairly smooth, with fainter growth lines more pronounced at sutures and very fine, wavy, spiral lines (Fig. 5 A); aperture oval, oblique. Shell whorls: 4–4 ½. Umbilicus is rather broad, ~ 1 ⁄ 6 of maximum shell diameter. Shell dimensions: 6–9 mm diameter, 3–4 mm height (Fig. 7). Aperture width: 2–4 mm. Radula (n = 3) composed of ~ 35 rows with 25–31 teeth / row (Fig. 8 B). Radular formula: C / 3 + 2–3 L / 3 + 0–1 LM / 2 + 9–13 M / 1.