This .NET class wraps the AcDbPolygonMeshVertex ObjectARX class. 

The PolygonMeshVertex class represents vertices within polygon meshes in AutoCAD.

Autodesk.AutoCAD.DatabaseServices.DBObject
    Autodesk.AutoCAD.DatabaseServices.Entity
        Autodesk.AutoCAD.DatabaseServices.Vertex
            Autodesk.AutoCAD.DatabaseServices.PolygonMeshVertex

Public Class PolygonMeshVertex
Inherits Vertex

public class PolygonMeshVertex : Vertex;

Do not derive from this class. Attempting to do so will cause your application to halt AutoCAD.

PolygonMeshVertex objects contain the Entity methods to set the entity properties such as color, layer, and linetype, but vertices are subentities that are supposed to have the same entity properties as the parent polygon mesh. So, using the Entity methods within the PolygonMeshVertex objects to change these properties to values other than those of the parent result in corrupt vertices (which audit can fix).

DBObject, Entity, PolygonMesh