ZS Pharma, a Fort Worth, Texas-based developer of treatments for kidney and liver disease, has raised $46 million in Series C funding. Alta Partners led the round, and was joined by RiverVest Venture Partners, 3×5 Special Opportunity Partners, Salem Partners and return backer Devon Park Bioventures.www.zspharma.com

Udacity, a Palo Alto, Calif.-based online learning startup, has raised $15 million in Series B funding.Andreessen Horowitz led the round, and was joined by return backers Charles River Ventures and Steve Blank. www.udacity.com

Zmags, a Boston-based provider of commerce-enabled digital catalogs and publications, has raised $6 million in new VC funding. North Atlantic Capital led the round, and was joined by return backers OpenView Venture Partners and NorthCap Partners. The company previously raised $12 million.www.zmags.com

Guanxi Inc., a Cayman Islands-based mobile social network services startup that recently spun out of mInfo, has raised an undisclosed amount of Series A funding,. SingTel Innov8 led the round, and was joined by Tim Draper.