Onchidium Buchannan, 1800

Dayrat, Benoit, Goulding, Tricia C., Apte, Deepak, Bhave, Vishal, Joseph Comendador,, Qua, ng, Ngo Xuan, Tan, Siong Kiat & Tan, Shau Hwai, 2016, Integrative taxonomy of the genus Onchidium Buchannan, 1800 (Mollusca, Gastropoda, Pulmonata, Onchidiidae), ZooKeys 636, pp. 1-40 : 7

Genus Onchidium Buchannan, 1800

Type species.

Onchidium typhae Buchannan, 1800, by monotypy.

Labella Starobogatov, 1976: 211. New synonym. Type species, by monotypy, Labella ajuthiae ( Labbé, 1935); replacement name of Elophilus Labbé, 1935, preoccupied by Elophilus Meigen, 1803 [ Diptera ].

Remarks.

The synonymy of Labella ajuthiae ( Labbé, 1935) with Onchidium stuxbergi (Westerlund, 1883) is discussed in the remarks on Onchidium stuxbergi . Labella is a junior synonym of Onchidium because the two generic names Labella and Onchidium apply to the same clade. Baker (1938) provided a list of misspellings and unjustified emendations of Onchidium : Onchidion , Onchydium , Orchidium , and Oncidium .

Diagnosis.

Body not flattened. No marginal glands in the notum. No dorsal gills. Dorsal eyes present on notum. Fully retractable, central papilla (with three dorsal eyes) present. Long eye tentacles. Male opening inferior to the right ocular tentacle, slightly to its left. Pneumostome medial. Intestine of types II and III. Rectal gland present. Accessory penial gland and hollow spine present. Penis with hooks.

Distinctive diagnostic features.

Onchidium differs from all other onchidiids by the presence of unmistakably, large, conical, pointed papillae on the dorsum of live animals. Disturbed live animals and preserved animals are retracted and their dorsal papillae are significantly smaller. The identification to the genus level can then be more challenging.

Distribution.

From north-eastern India (West Bengal) to the Philippines, including the Strait of Malacca, Singapore, Thailand, Vietnam, eastern Borneo, and China (Fig. 2).