Testa perniformis, obovata, substantia ligni antiqui, tumidiuscula, superficie obsolete rugosa, inæquali interne livida. Cardo transversus, margine inflexo, notatus crenis obtusis circiter 8.
ANOMIA.
The single species here mentioned was comprehended in Ostreum.
A. placenta. O. orbiculatum planum pellucidum.
Reference was made, by a long periphrasis, to plates 225, 226 of Lister's 'Historiæ'; Seba was not quoted: "intra discum testæ adnatis" was absent.
MYTILUS.
Testa opaca, læviuscula. Cardo nullis dentibus instructus, sed fossula obliqua intra marginem.
This definition very properly excluded the oysters which had been erroneously inserted in this genus. Only the Mytili and Modiolæ of Lamarck were left as members; for margaritiferus and hirundo were transferred to Ostreum!!
M. frons. Ost. acutum plicatum, labio altero scabro.
M. crista-galli. Ost. acutum, plicatum, labio utroque scabro.