Bouchetcamaena procumbens (Gould, 1844) Páll-Gergely & Ablett & Szabó & Neubert, 2022

Pall-Gergely, Barna, Ablett, Jonathan D., Szabo, Marton & Neubert, Eike, 2022, Revision of the " Chloritis delibrata (Benson, 1836) " group (Gastropoda, Stylommatophora, Camaenidae), ZooKeys 1086, pp. 1-31 : 1

Bouchetcamaena procumbens (Gould, 1844) comb. nov.

Figures 13 , 14 , 15

Helix procumbens Gould, 1844: 453, pl. 24, fig. 1.

Helix delibrata Hanley & Theobald, 1870: pl. 14, fig. 10.

Chloritis (Trichochloritis) delibrata var. procumbens Gude, 1914: 172-173.

Trachia delibrata f. procumbens Stoliczka, 1871: 225, pl. 16, figs 1-3 (reproductive anatomy, jaw, radula).

Chloritis delibrata var. procumbens Richardson, 1985: 93.

Type locality.

"Province of Tavoy in British Burmah" (from the title).

Types examined.

Tavoy, British Burmah, leg. F. Mason, MCZ 169311 (lectotype: labelled as holotype, see remarks).

Additional material examined.

white type: (1) Khasi Hills, Assam, (2) Burma, A.S. Kennard coll., Acc. No. 1824, NHMUK 20191136/1 (1 shell, mixed lot with B. foveata : NHMUK 20191136/2; the Khasi Hills material probably refers to Bouchetcamaena foveata , whereas the Burma material refers to Bouchetcamaena procumbens ); India, "Khasi Hills", NHMUK 1862.11.19.12 (2 shells); Moulmain, Tenasserim, coll. Stoliczka, NHMUK 1903.7.1.387 (1 shell); Pegu, ex coll. Godwin-Austen, NHMUK 1903.7.1.386 (1 shell); Pegu, NHMUK 1888.12.4.1114-1115 (2 shells); Tavoy, Burmah, Museum Cuming, NHMUK 20191137 (1 shell). darker type : Arakan, coll. H.F. Blanford, NHMUK 1909.3.15.25 (1 shell); Mutan, Tenasserim, coll. Godwin-Austen, NHMUK 20191133 (1 shell); Pegu, Arakan Hills, NHMUK 1906.2.2.121 (4 shells, one of them with widely-spaced pits, others with hardly visible scars, see remarks).

Diagnosis.

Shell small to medium-sized, with flat dorsal side or slightly sunken or very slightly elevated spire; aperture oval, peristome strongly expanded, umbilicus narrow and deep; sculpture variable: in some shells the thick, brown, matt periostracum makes hair scars practically invisible, in other shells the hair scars (pits) are usually densely arranged on the entire shell.

Description.

Shell medium-sized, rather thin-walled; dorsal side flat, very rarely (NHMUK 1906.2.2.121) slightly domed; shell shape “nautiliform” (i.e., initial whorls closely coiled, body whorl conspicuously expanded); colour whitish to light yellowish with somewhat darker yellowish, matt (dull) periostracum in some places, or, as in one sample (Mutan, Tenasserim), on the entire shell; a normally wide, faint reddish-brown belt running around the shoulder of the body whorl (can be entirely absent); protoconch consisting of 1-1.5 whorls, finely wrinkled and covered by hair scars (pits) or small, mamilla-like hairs; entire shell consisting of 3.75-4.75 whorls, separated by a deep suture; teleoconch finely and irregularly wrinkled; sculpture variable: in typical shells some darker yellowish-light brownish periostracum covers parts of the teleoconch, and the densely arranged hair scars are only visible in the suture on the dorsal side and near the parietal callus on the ventral side; in the "pitted form", hair scars densely arranged on entire shell and clearly visible on both the dorsal and ventral sides; aperture oval/subrectangular; peristome strongly expanded and slightly reflected in direction of umbilicus; palatal part with a thin, whitish, semi-transparent layer, with hair scars visible on penultimate whorl; umbilicus open, narrow, funnel-shaped, peri-umbilical keel blunt.

Measurements.

D = 15.8-19.5 mm, H = 7.8-9.4 mm (n = 7).

Differential diagnosis.

The smaller shell size and the more reflected peristome distinguish this species from the most similar species, B. delibrata . Furthermore, the "white type" B. procumbens differs from B. delibrata in the presence of dense and prominent hair scars.

Distribution.

Seems to be restricted to southern Myanmar.

Remarks.

Johnson (1964) mentioned that the figured “holotype” (MCZ 169311) is from the NYSM 232 (original no. A 567), and that there is a “paratype” (USNM 611226) from the same NYSM lot. Johnson’s listing of the specimen as a “holotype” has to be accepted as an indirect lectotype designation by inference of holotype (see ICZN Art. 74.6). Furthermore, two additional “paratypes” (= paralectotypes) are found in the MCZ (reg. no.: 87935, ex BSNH).

There are two forms of this species. One is lighter in colour, some of the specimens have a slightly sunken spire and possess uniformly arranged, strong hair scars on the entire surface of the shell ("white type"), whereas the other type has a darker shell (yellowish to light brownish) with hardly visible hair scars ("darker type"). The sample NHMUK 1906.2.2.121 contains four shells of identical appearance; however, one of them has widely-spaced pits, whereas the other three have only some pits on the callus area but otherwise no hair scars. Thus, it seems that the strength of the hair scars is variable within this species, unlike in all other species of this group. Since the shell and aperture shape are, with the exception of spire height, practically identical, and there are transitional forms between the two types in terms of shell sculpture, we provisionally treat them as one species. There are no clearly visible hair scars on the lectotype. Thus, the form without prominent hair scars is considered typical Bouchetcamaena procumbens , and the "pitted form" is considered atypical.

Figures

Figure 6. Positions of close-up images. Abbreviations: CA: callus; DM: middle of dorsal side; LV: last whorl; PC: protoconch. Not to scale.

Figure 13. Bouchetcamaena procumbens (Gould, 1844), comb. nov. A-D lectotype (MCZ 169311) E-I NHMUK 1862.11.19.12.

Figure 14. Bouchetcamaena procumbens (Gould, 1844), comb. nov. NHMUK 1903.7.1.386. For positions of close-up images see Fig. 6 (F = DM, G = CA, H: LV, I: PC).

Figure 15. Bouchetcamaena procumbens (Gould, 1844), comb. nov. NHMUK 1906.2.2.121. For positions of close-up images see Fig. 6 (F = DM, G = CA, H: LV, I: PC).