We consider the acceleration of superthermal ions within ripples on the surface of a fast-mode hydromagnetic shock. We confine attention to small-amplitude surface ripples, characterized by width L and amplitude A, that are large compared to an energetic ion's gyroradius rg, i.e., rg≪A≪L. Furthermore, we focus upon shocks that are quasi-perpendicular on average. To simplify the problem, we consider a perpendicular shock having a single surface ripple with a sinusoidal form. We investigate the effects of confinement, evolving geometry, and finite shock curvature that are associated with the ripple by integrating along the orbits of test particles (protons). We assume scatter-free motion away from the shock and quasi-static conditions. As an upstream magnetic field line convects through the surface ripple, it intersects the shock at two points, forming a temporary magnetic trap. A few particles injected into this trap undergo many reflections at the shock and are accelerated nonadiabatically (i.e., the first adiabatic invariant is not conserved) before being convected downstream. In some cases these particles form a high-energy power law tail on the energy spectrum. Large-amplitude, spike like flux enhancements of width ~rg are coincident with the shock passage. These spikes are superposed upon broader, but less intense, flux increases with widths that are energy-dependent but are typically ~A. Flux-time profiles and angular distributions in a given ripple vary markedly depending upon path through the ripple and distance from the shock. Angular distributions upstream range from unidirectional to bidirectional along the field, while those downstream are peaked nearly transverse to the field. The model-predicted results reproduce many features of observed ion shock-spike events, including their singly or multiply spiked impulsive structure, the variability of this structure with particle energy in a given event, and the large variety of structures observed from event to event. ¿ American Geophysical Union 1990