The first full amplitude analysis of B þ → J=ψϕK þ with J=ψ → μ þ μ − , ϕ → K þ K − decays is performed with a data sample of 3 fb −1 of pp collision data collected at ffiffi ffi s p ¼ 7 and 8 TeV with the LHCb detector. The data cannot be described by a model that contains only excited kaon states decaying into ϕK þ , and four J=ψϕ structures are observed, each with significance over 5 standard deviations. The quantum numbers of these structures are determined with significance of at least 4 standard deviations. The lightest has mass consistent with, but width much larger than, previous measurements of the claimed Xð4140Þ state. The model includes significant contributions from a number of expected kaon excitations, including the first observation of the K Ã ð1680Þ þ → ϕK þ transition.