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We present a spectroscopic study of eight extremely low-metallicity candidateemission-line galaxies with oxygen abundances possibly below 12 +log O/H =7.35. These galaxies were selected from Data Release 10 of the Sloan DigitalSky Survey/Baryon Oscillation Spectroscopic Survey (SDSS/BOSS DR10). We willcall these extremely metal-deficient galaxies XMD galaxies. The electrontemperature-sensitive emission line [O~{\sc iii}] $\lambda$4363 is detected inthree galaxies and marginally detected in two galaxies, allowing for abundancedetermination by a "direct" method. Because of large uncertainties in the [O{\sc iii}]$\lambda$4363\AA\ line fluxes, we also calculated oxygen abundance inthese galaxies together with the remaining three galaxies using a strong-linesemi-empirical method. This method gives oxygen abundances higher than 7.35 forthree galaxies with detected [O {\sc iii}]$\lambda$4363\AA\ line and lower than7.35 for the remaining five objects of the sample. The newly-discoveredgalaxies represent excellent targets for follow-up spectroscopic observationswith the largest telescopes to improve the oxygen abundance determination andto increase the number of these very rare low-metallicity objects. The extremelocation of the most massive and luminous XMD galaxies and XMD candidates inthe stellar mass-metallicity diagram implies that these galaxies may be genuineyoung objects.  With stellar masses of up to $\sim$ 10$^7$ - 10$^8$$M_{\odot}$, the galaxiesare not chemically enriched and strongly deviate to lower metallicity ascompared to the relation obtained for a large sample of low-redshift,star-forming galaxies.

New candidates for extremely metal-poor emission-line galaxies in the SDSS/BOSS DR10