San Francisco -- PapayaMobile, the San Francisco-based developer of a social gaming network for the Android platform, said on Wednesday it has raised $18 million in its second round of funding, co-led by Keytone Ventures and DCM. The company plans to use the proceeds to expand its developer ecosystem in both the U.S. and Europe, while strengthening its portfolio of products. PapayaMobile hosts mobile games on its social network, which includes more than 15 million users. The company's platform also offers tools designed to help mobile developers build social games. "As our momentum on Android continues to grow, our latest funding… will help us continue to expand our social network across the globe," said Si Shen, the co-founder and CEO of PapayaMobile.