How to add a new Visual C# Project in Visual Studio 2013?

How to add a new Visual C# Project (*.csproj) to an existing solution in Visual Studio 2013 as the ones shown in the picture below? (Northwind.Model, Northwind.Repositories and Northwind.Repositories.Entity):

What type of project do I have to select in the "New Project" dialog? I do not see that rectangular icon with the string "C#" in any of the project templates available!

Thanks in advance