RESUMO Omalonyx geayi Tillier, 1980 foi originalmente descrita com base em exemplares procedentes do pântano Kaw na Guiana Francesa. A espécie se diferencia das demais de Omalonyx d'Orbigny, 1837: (i) pelo ducto hermafrodita duas vezes mais longo e convoluto, cuja inserção no ovariotestis é em formato de um funil, ao invés de ductos radiais, e (ii) pelas pregas longitudinais enrugadas na parede interna do falo. Dois lotes - procedentes de Trinidad e Carauari (Amazonas, Brasil) - apresentaram espécimes com ovariotestis e ducto hermafrodita similares aos da descrição original de O. geayi, porém com a morfologia do falo distinta. Outros oito lotes procedentes do Suriname, Equador, Brasil (estados do Amazonas e Alagoas), Bolívia e estrada Cayenne-Kourou na Guiana Francesa continham exemplares com morfologia do falo análoga à de O. geayi, todavia com ovariotestis e ducto hermafrodita similares aos das demais espécies de Omalonyx. Conforme resultados do estudo histológico e da análise filogenética com caracteres morfológicos, concluímos que as condições mencionadas para o ovariotestis e ducto hermafrodita na descrição de O. geayi foi baseada em espécimes parasitados. Omalonyx geayi é redescrita e novas informações sobre a distribuição na América do Sul são apresentadas.

ABSTRACT Omalonyx geayi Tillier, 1980 was originally described on the basis of specimens from Kaw swamp, French Guiana. This species distinguished from other of Omalonyx d'Orbigny, 1837: (i) by hermaphrodite duct twice as long and sacculate, without radial ducts but a funnel-shaped insertion on the ovariotestis, and (ii) by longitudinal wrinkled folds on the phallus inner wall. Two recent collections - from Trinidad and Carauari (Amazonas, Brazil) included specimens with ovariotestis and hermaphrodite duct morphologies similar to that originally described for O. geayi, but with phallus morphology not consistent with identification as O. geayi. A further eight lots, from Suriname, Ecuador, Brazil (Amazonas and Alagoas States), Bolivia and Cayenne-Kourou Road in French Guiana comprised specimens with phallus morphology analogous to O. geayi and ovariotestis and hermaphrodite duct similar to that of other Omalonyx species. Based on histological examination, and earlier phylogenetic analyses of morphological characters, we conclude that the ovariotestis and hermaphrodite duct conditions previously described for O. geayi were based on parasitized specimens. Accordingly, O. geayi is redescribed, and new information presented on the species' wide distribution in South America.

Macrocyclis peruvianus (Lamarck, 1822) é um grande caracol terrestre endêmico do Chile. Uma descrição detalhada da esculturação de sua concha, rádula, mandíbula, cavidade palial e sistema reprodutor são apresentados aqui pela primeira vez.

Macrocyclis peruvianus (Lamarck, 1822) is a large terrestrial snail which is endemic in Chile. A detailed description of its shell structure, jaw, radula, palial cavity and reproductive system is presented here for the first time.

Simpulopsis promatensis e S. gomesae, duas novas espécies para São Francisco de Paula, Rio Grande do Sul, Brasil, são descritas. São apresentadas a conquiliologia, conquiliometria e morfologia das partes moles, incluindo mandíbula, rádula, sistemas reprodutor e palial.

Simpulopsis promatensis and S. gomesae, two new species from São Francisco de Paula, Rio Grande do Sul state, Brazil are described. Conchology, conchiliometry and soft-part morphology, including jaw, radula, reproductive and pallial systems are provided.

The population growth of Simpulopsis ovata (Sowerby, 1822) from the Centro de Pesquisas e Conservação da Natureza - Pró-Mata, São Francisco de Paula, Rio Grande do Sul, Brazil, was studied along eleven months of 1996. Two discontinuous age classes were identified. The first one, with a monthly growth rate of 1.55 mm, was reproductively mature during April and May. The second one appeared after the previous group and had a monthly growth rate of 0.44 mm. The fact that no adults from the two age classes were found together is a characteristic of a semelparous species. New insights about its shell, pallial cavity and reproductive system are given. This is the first record of S. ovata for the State of Rio Grande do Sul.

The changes in gonadal development in male and female of Donax hanleyanus Philippi, 1847 are described. Gonad development and spawning seasons were assessed by monthly sampling of population from Arroio Teixeira beach, southern Brazil. Histological examination of clams showed in the most of the adult population sampled that the spawning is practically continuous, without any period of sexual rest. There are two main periods of gametogenesis, in winter and in summer, being the degree of maturation longer in the latter. The water temperature is stimulant on gametes proliferation and spawning.

Old descriptions of species frequently present imprecise or even non-existing toponyms. Based on comparisons of old collecting maps by HENSEL (1867), it is suggested the river basin to which belongs the material collected and designed as a new species (Rio Caí basin), namely Chilina parva Martens, 1868. The type-locality of this material, Rödersberg, can hardly be categorically affirmed, but as coordinates were raised, along other evidences, it is suggested that the actual toponym be Morro Reuter county, Rio Grande do Sul.