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We use the Space Telescope Imaging Spectrograph on board the Hubble SpaceTelescope to obtain new high-quality spectra covering the 1900 to 2360 Angstromwavelength range for two metal-poor stars, HD 108317 and HD 128279. We deriveabundances of Cu II, Zn II, As I, Se I, Mo II, and Cd II, which have not beendetected previously in either star. Abundances derived for Ge I, Te I, Os II,and Pt I confirm those derived from lines at longer wavelengths. We also deriveupper limits from the non-detection of W II, Hg II, Pb II, and Bi I. The mean[As/Fe] ratio derived from these two stars and five others in the literature isunchanged over the metallicity range -2.8 < [Fe/H] < -0.6, <[As/Fe]> = +0.28+/- 0.14 (std. dev. = 0.36 dex). The mean [Se/Fe] ratio derived from these twostars and six others in the literature is also constant, <[Se/Fe]> = +0.16 +/-0.09 (std. dev. = 0.26 dex). The As and Se abundances are enhanced relative toa simple extrapolation of the iron-peak abundances to higher masses, suggestingthat this mass region (75 < A < 82) may be the point at which a differentnucleosynthetic mechanism begins to dominate the quasi-equilibrium alpha-richfreezeout of the iron peak. <[CuII/CuI]> = +0.56 +/- 0.23 in HD 108317 and HD128279, and we infer that lines of Cu I may not be formed in localthermodynamic equilibrium in these stars. The [Zn/Fe], [Mo/Fe], [Cd/Fe], and[Os/Fe] ratios are also derived from neutral and ionized species, and eachratio pair agrees within the mutual uncertainties, which range from 0.15 to0.52 dex.

New Detections of Arsenic, Selenium, and Other Heavy Elements in Two Metal-Poor Stars