Alterian, a London-based marketing services company, has bought online content manager Mediasurface. Shares of the combined company are expected to begin trading on July 9 on the London Stock Exchange, but apart from that, financial terms were not disclosed. Alterian said its purchase of Mediasurface, which also has offices in the U.S., will allow it to offer a wider array of behavioral analytics to the ad agencies its works with, including WPP Group’s Ogilvy One and Havas’ Euro RSCG Worldwide. Release