Plectopylidae Mollendorff 1898

Family Plectopylidae Möllendorff, 1898

Plectopylidae Möllendorff, 1898: 147.

Type genus

Plectopylis Benson, 1860.

Diagnosis

Shell sinistral or dextral, small to very large (5–35 mm); flat, depressed-conical or conical; dorsal surface concave, flat (even in those cases the protoconch usually protrudes above surface), conical or domed; protoconch sculpture variable between genera (ribbed, wrinkled, reticulated, tuberculated); dorsal surface usually with reticulated structure (consisting of spiral and radial lines); ventral surface usually with less prominent sculpture; deciduous periostracal folds might be present on the periphery of body whorl; aperture oblique to shell axis; peristome expanded, sometimes reflected; parietal callus present, V- or slightly S-shaped, apertural fold present or absent; multiple armatures formed during growth, the last one 0.25–0.75 whorls behind aperture; parietal wall with one or two vertical lamellae, usually with additional horizontal plicae above and below the lamellae or anterior to them; palatal wall with 6–7 plicae, which are variable in morphology: straight and horizontal, depressed Z-shaped, sometimes divided in the middle (most often when there is a single parietal lamella), or the fourth and fifth fuse to each other, forming a vertical plate (most often where there are two parietal lamellae).

Ommatophoral retractor (in sinistral specimens the left, in dextral specimens the right retractor) runs between the penis and vagina; atrium short; penis very short, vestigial to well-developed, without verge, usually with parallel folds internally; calcareous crystals may be present between folds; epiphallus usually present, bound to penis by weak fibres; penial caecum short or absent, retractor muscle inserts on penial caecum or, if caecum is absent, at the penis-epiphallus transition; vas deferens long, usually thickened before entering spermoviduct; vagina well-developed, usually U-shaped, sometimes with thickened ‘vaginal bulb’ formed at turning point of ‘U’, attached to body wall with multiple, short muscle fibres; vagina internally with longitudinal folds; spermoviduct long; bursa copulatrix with slender stalk of variable length and usually an ovoid bursa; diverticulum usually present, short ovoid to very long, slender, usually originates near originating point of bursa copulatrix; all species ovoviviparous, embryo sac with several small calcareous crystals on its surface; talon normally developed, elongated, albumen gland of variable length.

Radula elongated, but not very slender; teeth arranged in rows; laterals in straight rows perpendicular to central column; marginals in anteriorly pointed, slightly oblique rows, central tooth with a single, small to medium-sized cusp (sometimes absent), which is smaller or larger than ectocones of first laterals, but always smaller than endocones of first laterals; first laterals with a large endocone and a small ectocone; transition between laterals and marginals is gradual with endocone being gradually divided into two cusps, ectocones usually remain undivided.

Distribution

The family Plectopylidae extends from the southern Himalayan region (Nepal and northeastern India) throughout Myanmar, the Malay Peninsula, southern and northern Thailand, northern Laos, northern Vietnam, central, southern and eastern China (Yunnan, Sichuan, Guizhou, Chongqing, Hubei, Hunan, Guangxi, Guangdong, Jiangxi, Zhejiang and Fujian Provinces) to Taiwan and southern Japan (Miyako Island) (Fig. 3).