  The U. C. Berkeley Infrared Spatial Interferometer has been outfitted with a
filterbank system to allow interferometric observations of mid-infrared
spectral lines with very high spectral resolution (R ~ 10^5). This paper
describes the design, implementation, and performance of the matched 32-channel
filterbank modules, and new spectral line observations of Mars and IRC+10216
are used to demonstrate their scientific capability. In addition, observing
strategies are discussed for accurate calibration of fringe visibilities in
spectral lines, despite strong atmospheric fluctuations encountered in the
infrared.
