The stability of a spherical shell ion distribution function against low-frequency hydromagnetic waves is discussed by relaxing the assumption of parallel propagation which was imposed in the preceding discussions published in the literature. It is found that Alfv¿n waves as well as magnetosonic waves with olbique angles of propagation can be excited by a shell distribution. In the present analysis, the emphasis is placed on the case in which the thickness of the spherical shell is small. ¿ American Geophysical Union 1990