they played a role in motivating this project. Both UGC 4393 and UGC 10818 were identified by @engelbracht08 as low metallicity outliers from the global trend of 70/160 $\mu$m color temperature as a function of metallicity. These two galaxies affect the interpretation of the trend for aromatic emission to weaken below 12 + log(O/H) = 7.9 in the mid-IR [see e.g., @engelbracht08] and the far-IR [see e.g., @draine07; @engelbracht08]. Because of the possibility that these objects’ oxygen abundances were underestimated using the lower branch of the R$_{23}$ calibration [@pilyugin05], they were included in this sample to be re-examined (see discussion in Appendix \[sec:outlier\]). See Table \[tbl1\] for sample characteristics.

DATA
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MMT Spectra {#sec:mmt}
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### Observations {#sec:mmtobs}

New spectroscopy was acquired at the MMT in order to achieve high signal-to-noise (S$/$N) spectra with the goal of detecting the faint \[\] $\lambda$4363 auroral line at a strength of 4$\sigma$ or higher. The observations were obtained with the Blue Channel spectrograph [@schmidt89] on the UT dates of 2008 October 30-November 1, 2009 June 15-22, and 2010 January 11-12. Sky conditions varied, but contained minimal cloud coverage and approximately arcsecond seeing. A 500 line grating, $1\arcsec$ slit, and UV-36 blocking filter were 