Subgeneric Relationships in the Euthecosomatous Pteropod Genus Llmacina Bosc, 1817

Summary

The relationships between the species of the genus Limacina are examined and a new subgeneric classification based on anatomical characteristics is proposed The subgenus Limacina Bosc, 1817, includes five species: L bulimoides (d’Orbigny, 1836). L helicina (Phipps, 1774), L lesueuri (d’Orbigny, 1836). L retroversa (Fleming. 1823), and L trochiformis (d’Orbigny, 1886). The subgenus Limacina is characterized primarily by a dorsal mantle cavity, pallial gland of one cell zone, and a common pattern of reproductive morpbology. Free-floating egg masses are deposited by all five species. The subgenus Thilea Strebel, 1908, includes a single species. L helicoides Jeffreys, 1877, which has the mantle cavity offset to the right side and a pallial gland of two cell zones. The reproductive morphology of L helhicoides is similar to that of the subgenus Limacina. but encapsulated young are retained in the mucous gland of the female and the species is ovoviviparous. The subgenus Embolus Jeffreys, 1870, has the single species Limacina inflata (d’Orbigny, 1836). The reproductive morphology of L inflata is substantially different from the other species of the genus; the mucous and albumen glands and the penis are absent in L inflata and the prostate gland develops into a spermatophore. Females of L inflata retain developing embryos in the mantle cavity where they are attached to the mantle lining