Chersaecia Gude, 1899

Pall-Gergely, Barna, Budha, Prem B., Naggs, Fred, Backeljau, Thierry & Asami, Takahiro, 2015, Review of the genus Endothyrella Zilch, 1960 with description of five new species (Gastropoda, Pulmonata, Plectopylidae), ZooKeys 529, pp. 1-70 : 7-8

Taxon classification Animalia Pulmonata Plectopylidae

Genus Chersaecia Gude, 1899

Chersaecia 1899c Chersaecia (section of the genus Plectopylis ) Gude: Science Gossip, 6: 148.

Chersaecia 1999 Chersaecia , - Schileyko: Treatise on Recent Terrestrial Pulmonate Molluscs, Part 4. (...): 2: 462.

Type species.

Helix (Plectopylis) Leiophis Benson, 1860 (Figure 2) by original designation.

Diagnosis.

Shell sinistral or dextral, flat, widely umbilicated; in most cases protoconch seemingly “smooth” to the naked eye, but not glossy, rather matt; under the microscope usually tubercles of various size are visible (Figure 2B); sometimes the tuberculated protoconch is irregularly wrinkled; flat periostracal filaments are visible on the body whorl or on the dorsal surface in only a few species; aperture always with a fold; parietal wall with one vertical lamella and usually one or two long horizontal plicae (main plica and lower plica) reaching the callus; palatal plicae horizontal, sometimes divided in the middle, in some species with several additional denticles posteriorly, in some species similar to that of Plectopylis (three horizontal plicae above and one below the vertical plate formed by the accretion of two plicae).

Only one Chersaecia species is known anatomically ( Chersaecia simplex in the original description: Solem 1966). Penis internally with approximately eight longitudinal rows, those situated next to the vas deferens are distinctly larger; vas deferens becomes a part of the penis wall at the penioviducal angle; no epiphallic differentiation observed; retractor muscle inserts on the dorsal surface of the penis and attaches to the diaphragm; diverticulum absent, gametolytic sac long and thickened.

Differential diagnosis.

Chersaecia differs from Endothyrella , Gudeodiscus Páll-Gergely, 2013, Halongella Páll-Gergely, 2013, Sicradiscus Páll-Gergely, 2013 and Sinicola by the usually tuberculated (not regularly ribbed) protoconch. The presence of long parietal plicae (main and lower) distinguishes most Chersaecia species from most Endothyrella , Gudeodiscus , Halongella , Sicradiscus and Sinicola species. The delimitation of Chersaecia from Plectopylis and Endoplon needs further investigation. Among all plectopylids examined to date Chersaecia simplex is the only species found to lack an epiphallus. The anatomy of more Chersaecia species should be studied to check the taxonomic value of the lack of the epiphallus.

Content.

austeni , brachydiscus , degerbolae , dextrorsa , kengtungensis , leiophis ( pseudophis is probably a synonym, see Gude 1908a), muspratti , nagaensis , perarcta , perrierae , refuga , shanensis , shiroiensis , simplex .

Distribution.

The genus is known to inhabit northeastern India, eastern and southern Myanmar (Burma) and northern Thailand.