As Amazon’s Marketplace continues to grow and mature, a new opportunity has emerged in the world of e-commerce for a new breed of startups to consolidate the most promising of the smaller businesses that sell via Amazon’s platform, and build out their own economies of scale within that ecosystem. In the latest development, SellerX — a new outfit in Berlin — has closed a round of $118 million (€100 million) that it plans to use to roll up smaller enterprises that use Fullfilment by Amazon for payments, logistics and delivery for their products.