 Shares of special purpose acquisition company Tortoise Acquisition NYSE: SHLL were trading higher on Wednesday as intense investor interest in the companys pending deal to merge with electric heavy-truck start-up Hyliion continued to drive gains. As of 2:45 p.m. EDT, Tortoises shares were up about 8.7 from Tuesdays closing price. Tortoise is a special purpose acquisition company SPAC, meaning a company that has no business plans of its own but that seeks to acquire other businesses. 