This .NET class wraps the AcGePointOnCurve3d ObjectARX class. 

It represents a point on a 3D parametric curve. This class encapsulates all of the geometric information of a point on a 3D curve including its parameter value, 3D coordinates, and derivatives.

Autodesk.AutoCAD.Geometry.Entity3d
    Autodesk.AutoCAD.Geometry.PointEntity3d
        Autodesk.AutoCAD.Geometry.PointOnCurve3d

Public sealed Class PointOnCurve3d
Inherits PointEntity3d

public sealed class PointOnCurve3d : PointEntity3d;