Low-temperature FTIR spectroscopy of bacteriorhodopsin and xanthorhodopsin was used to elucidate the number of K-like bathochromic states, their sequence, and their contributions to the photoequilibrium mixtures created by illumination at 80-180 K. We conclude that in bacteriorhodopsin the photocycle includes three distinct K-like states in the sequence bR ->(hv)l*-> J -> K-0 -> K-E -> K-L -> L ->..., and similarly in xanthorhodopsin. K-0 is the main fraction in the mixture at 77 K that is formed from J. K-0 becomes thermally unstable above similar to 50 K in both proteins. At 77 K, both J-to-K-0 and K-0-to-K-E transitions occur and, contrarily to long-standing belief, cryogenic trapping at 77 K does not produce a pure K state but a mixture of the two states, K-0 and K-E, with contributions from K-E of similar to 15 and similar to 10% in the two retinal proteins, respectively. Raising the temperature leads to increasing conversion of KO to KE, and the two states coexist (without contamination from non-K-like states) in the 80-140 K range in bacteriorhodopsin, and in the 80-190 K range in xanthorhodopsin. Temperature perturbation experiments in these regions of coexistence revealed that, in spite of the observation of apparently stable mixtures of K-0 and K-E, the two states are not in thermally controlled equilibrium. The K-0-to-K-E transition is unidirectional, and the partial transformation to K-E is due to distributed kinetics, which governs the photocycle dynamics at temperatures below similar to 245 K (Dioumaev and Lanyi, Biochemistry 2008, 47, 11125-11133). From spectral deconvolution, we conclude that the K-E state, which is increasingly present at higher temperatures, is the same intermediate that is detected by time-resolved FTIR prior to its decay, on a time scale of hundreds of nanoseconds at ambient temperature (Dioumaev and Braiman, J. Phys. Chem. B 1997, 101, 1655-1662), into the K-L state. We were unable to trap the latter separately from K-E at low temperature, due to the slow distributed kinetics and the increasingly faster overlapping formation of the L state. Formation of the two consecutive K-like states in both proteins is accompanied by distortion of two different weakly bound water molecules: one in K-0, the other in K-E. The first, well-documented in bacteriorhodopsin at 77 K where K-0 dominates, was assigned to water 401 in bacteriorhodopsin. The other water molecule, whose participation has not been described previously, is disturbed on the next step of the photocycle, in K-E, in both proteins. In bacteriorhodopsin, the most likely candidate is water 407. However, unlike bacteriorhodopsin, the crystal structure of xanthorhodopsin lacks homologous weakly bound water molecules.