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We report on a search for weak-line T~Tauri stars (wTTS) in the vicinity of the Taurus--Auriga star forming region. For ground-based optical follow-up observations we have selected unidentified X-ray sources from the ROSAT All-Sky Survey. So far, we have performed high-resolution spectroscopy with CfA-echelle-spectrographs for $109$ unidentified X-ray sources south of the Taurus molecular clouds in order to measure their radial velocity to test kinematic membership to Taurus. Additional mid-resolution spectra obtained for $40$ sources so far show that $15$ of them have spectra typical of wTTS, exhibiting weak $H \alpha$ emission and Lithium $6708$ \AA~absorption. Seven of these new wTTS have radial velocities between $13$ and $21~km/s$, i.e. consistent with membership to Taurus. Hence, the Taurus--Auriga star forming region seems to extend much further south than previously assumed. These new TTS lie far from regions of ongoing star formation, and it is not clear whether they were formed in clouds cores in central Taurus and moved to their present locations, or whether they were formed near their present locations. We plan to extend the search to find the borders of the Taurus T association. All TTS known in Taurus prior to the ROSAT mission are located in or near molecular clouds, namely in an area given by $4~h \le \alpha \le 5~h$ and $14^{\circ} \le \delta \le 35^{\circ}$. The region we plan to study surrounds this central Taurus region by $10$ deg wide strips.
