Chersaecia nagaensis nagaensis (Godwin-Austen, 1875)

Páll-Gergely, Barna, 2018, Systematic revision of the Plectopylinae (Gastropoda, Pulmonata, Plectopylidae), European Journal of Taxonomy 455, pp. 1-114 : 46-49

Chersaecia nagaensis nagaensis (Godwin-Austen, 1875)

Figs 21G–I, 22A

Helix (Plectopylis) nágáensis Godwin-Austen, 1875b: 609–610 , 612, pl. 73, fig. 4 [“Prowi, head of the Lauier river, Nágá hills, 5000 feet ”] (partim).

Helix (Plectopylis) nagaensis – Nevill 1878: 72. — Tryon 1887: 161, pl. 35, figs 78–79.

Plectopylis nagaensis – Gude 1897a: 206–207, fig. 33a–d.

Plectopylis (Chersaecia) nagaensis – Gude 1899d: 148; 1899e: 175; 1914b: 96–97, fig. 42a–d. Chersaecia nagaensis – Páll-Gergely et al. 2015c: 10.

Diagnosis

Main plica present.

Material examined

Types

INDIA: 10 shells, syntypes of P. nagaensis , Naga Hills, Prowi, head of Lanier Valley, coll. Godwin- Austen ( NHMUK 1903.7.1.753).

Additional material

INDIA: 1 shell, Japvo Pk, Naga Hills ( NHMUK 1903.7.1.3493); 2 adult shells (+ 2 juv. of questionable identity), Manipur Hills, Ogle leg. ( NHMUK 1903.07.01.777); 1 shell, Naga Hills, Ogle leg., coll. Godwin-Austen ( NHMUK); 9 shells, Prowi, NE Manipur, coll. Godwin-Austen ( NHMUK); 1 shell, Naga Hills, Hungerford leg. ( NHMUK 1891.3.17.352); 2 shells, coll. Godwin-Austen ( NHMUK 1909.3.26.74); 2 shells, Naga Hills ( NHMUK).

Description

SHELL. Sinistral, usually with dense brownish periostracum; two shells lacking periostracum had yellowish grey colour and densely alternating reddish and yellowish stripes on the dorsal surface; below periostracum shell surface very finely reticulated as a result of fine, dense radial ribs and nearly equally strong spiral striation; spire elevated, dorsal side domed/depressed conical; protoconch consists of 2.5–2.75 whorls, very finely granular, only last ca one whorl with rough irregular, radial sculpture; whorls 6.25–6.5; teleoconch whorls separated by a shallow suture; aperture rounded; peristome whitish, expanded and reflected; parietal callus slightly S-shaped, approximately as strongly developed as peristome; apertural fold strong, connected to parietal callus; umbilicus relatively narrow and deep, funnel-shaped.

Four opened shells were examined. Parietal side with a single lamella; both ends of lamella slightly elongated posteriorly; lamella with a very slight elongation anteriorly in position of intermediate plica; an opened shell (“ India ”, NHMUK 1874.9.26.3) with a short intermediate plica free from lamella; main plica free from lamella, reaching apertural fold; lower plica short, situated under the lamella, slightly extends beyond lamella in both anterior and posterior directions. Palatal wall with six plicae; first curved and situated near suture; second considerably elongated anteriorly, with an additional, small denticle at its posterior end; above this denticle there is another tiny denticle; third and fourth plicae shorter than second, slightly depressed Z-shaped; fifth plica shorter than fourth, divided in the middle (only visible from inside); sixth plica short, situated near suture, and positioned under the line of posterior denticles/ posterior parts of divided plicae.

MEASUREMENTS (in mm). D = 11.6–12.2, H = 6.3–6.8 (n = 3, type series of nagaensis ).

Differential diagnosis

The main plica is long, and connected to the apertural fold (absent in Chersaecia nagaensis muspratti ).

Distribution

All known localities are within the Naga Hills and Manipur, northeastern India.

Remarks

The ‘dwarfed variety’ of Plectopylis nagaensis , which was mentioned in the original description of the species, is described here under the name Chersaecia shiroiensis subnagaensis subsp. nov.