TGC Industries Inc. (Nasdaq: TGE) shares soared 14.5% to $7.82, on volume of 603,000 shares, or eight times its daily volume, after Dawson Geophysical Co. (Nasdaq: DWSN) said it would acquire the provider of seismic data to oil and gas producers for about $157 million in stock. DWSN shares advanced 1.1% to $43.00.

Cisco Systems (Nasdaq: CSCO) dealt in 24.7 million shares, catching up rapidly on a daily average of 71.2 million. Share prices gained 1.9% to $17.47.

XenoPort Inc.(Nasdaq: XNPT) shares fell 10.3% to $5.98, on volume of 4.4 million, or nine times its daily volume, after the company said it would halt development of its experimental heartburn treatment.