Bulimulus beckianum

Beckianum beckianum (Pfeiffer, 1846)

(Figs. 51 –55)

Synonymy see Tillier (1981).

Diagnostic features. Shell of about 6.5 mm. Color pale brown, translucent. Periostracum thin, shining. Outline turriform; width ~35% of length (Figs. 51–53). Protoconch of 2.5 whorls, glossy, tall, suture well-marked; smooth; occupying ~14% of shell length and ~32% of shell width (Figs. 54 –55); border protoconch-teleoconch unclear, orthocline. Spire of ~7 rounded, narrow whorls, growth of whorls continuous up to fourth whorl, angle ~40° (Figs. 54 –55); remaining whorls of similar size (Figs. 51–53); suture well-marked. Sculpture uniform series of axial, narrow ribs, from suture to suture, ~ 40 in penultimate whorl; interspaces between ribs equivalent to 4 times their width. Peristome not deflected, orthocline (Fig. 52). Aperture rounded, occupying ~20% of shell length and ~45% of width; lacking teeth; outer lip rounded, simple; inner lip highly concave, superior half slightly convex, inferior half also almost straight and narrow. Callus thin inconspicuous. Umbilicus absent.

Measurements (in mm): MZSP 112411: 6.5 by 2.2; MZSP 111842: 4.8 by 2.2.

Distribution. Only known from type locality.

Habitat. Caatinga semi-dry environment; collected inside caves.

Material examined. BRAZIL. Piauí; Serra da Capivara; Coronel José Dias municipality, close to Sítio do Mocó town, Cave Toca de Cima dos Pilão, 8°51’47.10”S 42°33’26.96”W, MZSP 112411, 1 shell, MZSP 111842, 1 shell (R. Casati col, 2012).

Systematic remarks. The main character of the genus Beckianum is the narrow whorls in their height, producing a multispiral, narrow whorled, turriform shell. The examined specimens clearly possess these characters. As the genus has a single species— B. beckianum, from Mexico to São Paulo—(Simone, 2006, and references therein) there is that single species to identify. However, the examined specimens have a more developed axial sculpture and a protoconch with 1 more whorl if compared with the typical B. beckianum (Simone, 2006, fig. 685). Despite these differences, the description of a new species is considered premature.

The extraordinary distribution of B. beckianum is possibly an indicative of anthropic transportation, as well as that under this epithet may exist several similar-shelled species. Further studies are certainly necessary as normal for subulinids.