Odostomia

Abstract: On an intertidal sandflat in western Kyushu, Japan in 1979, the trochid gastropod,Umbonium (Suchium) moniliferum (Lamarck), and the thalassinidean ghost shrimp,Callianassa japonica Ortmann, densely inhabited the lower and upper zones, respectvely.Callianassa japonica subsequently expanded its distribution range considerably, having occupied almost the entire sandflat by 1983. Concurrently, theU. moniliferum population gradually declined, becoming extinct in 1986. Furthermore, the populations of 9 species associated withU. moniliferum (predators, an ectoparasite, and subsequent inhabitants of emptyU. moniliferum shells) had disappeared by the end of 1992. The extinction processes ofU. moniliferum and the two other most numerically dominant species, the ectoparasitic gastropod,Odostomia sp., and the hermit crab,Diogenes nitidimanus Terao, were described in detail. It is believed that the bioturbation of sediments byC. japonica was responsible for the extinctions, possible mechanisms involved being discussed. This is the first documented record of the extinction of a large part of a macrobenthic assemblage centering on a filter-feedingUmbonium species which is characteristic of the benthic communities on many intertidal sandflats extending from Japanese to Southeast-Asian waters.

Abstract: The large fossils from the buried beaches near Nome, Alaska, are allocated to their respective positions in the sequence of deposits, and the Mollusca, Brachiopoda, Bryozoa, and Cirripedia are described and illustrated. New forms are described by MacNeil in the gastropod genera Cylichnella (Bullinella), Oenopota, Mohnia, Columbella (Astyris), Epitonium (Boreoscala), Odostomia (Iolaea), Tachyrhynchus, and Solariella (Machaeroplax); and in the pelecypod genera Crenella, Astarte, Cardita (Cyclocardia), and Cardium (Cerastoderma). A new form is described by Pilsbry in the cirrepede genus Verruca. It is inferred from the fauna that the relative ages of the beaches determined on physical grounds is correct, i.e., from younger to older, the Second Beach, the Intermediate Beach, and the Inner Submarine Beach; further, that the age of the Intermediate and Inner Submarine Beaches is Pliocene and of the Second Beach possibly Pleistocene. The fauna suggests that warmer waters than those of the present prevailed while the beaches were forming.

Abstract: 1. Six east North American odostomioid species (Gastropoda: Pyramidellidae) are shown to have spermatophores that are species-specific in structure and position. The spermatophores of Boonea seminuda, B. bisuturalis and B. impressa are stuck in the mantle cavity; those of Fargoa dianthophila, F. bushiana and F. bartschi are attached to the shell in a constant position.2. A supraspecific classification based on spermatophores does not accord with the traditional ones based on shell sculpture. By comparing all available lines of evidence, the spermatophore classification is shown to accord more closely with phyletic relationships. Shell sculpture has converged and diverged evolutionarily and is therefore unreliable in supraspecific pyramidellid systematics. With due allowances for variation it is, however, useful at the species level.3. The new genus Boonea is named, based on spermatophore and other data, with "Odostomia" seminuda as type-species.4. Reasons are given for using the name F. bartschi for "O. m...