to be attributable to FeH from lower resolution studies (Jones et al.1996; McLean et al. 2000). These features occur at 1.2091, 1.2113, 1.2135 and 1.2221 $\mu$m. Cushing et al. (2003) verified the features at 1.1939 and 1.2389 $\mu$m as the 0–1 and 1–2 band heads of the F$^{4}\Delta$ – X$^{4}\Delta$ system of FeH, and attributed a blended feature described by McLean et al. (2000) at 1.2221 $\mu$m as the F$^{4}\Delta_{7/2}$ – X$^{4}\Delta_{7/2}$ Q-branch. These authors also listed 24 other relatively strong features lying within the $J$-band. In the Cushing et al. list, no FeH features were identified in the wavelength interval covered by our order 65, which includes the strong shorter-wavelength doublet of K I, and only one feature (at 1.2464 $\mu$m) was tabulated for order 61, where the other K I doublet dominates.

To identify many more of the complex fine-scale features seen in the spectral sequences of Figures 1–6, we analyzed opacity (cross-section) data for both FeH and H$_{2}$O, (R. Freedman 2003, private communication) and utilized the FeH line list and transition catalog by Phillips et al. (1987). We are also grateful to Adam Burrows who provided CrH opacity data (Burrows et al. 2002) and Linda Brown who 