Geometry in Studio is divided in more than one way. The first would be by material zone. So on genesis this would be 3_SkinHand is a materia zone. The second is by selection set(this is not required) and this is more of a mapping from bone to facets. So you click on the eye(even thogh all the geometry is on the root object) the selection set tell Studio what node you meant to select.
If material zone is what you want then something along this line, assuming you have the root of the figure selected.
// have not compiled this, but I think you get the basic idea.
DzNode* node = dzScene->getPrimarySelection();
DzObject* object = node->getObject();
DzShape* shape = object->getCurrentShape();
DzFacetMesh* mesh = qobject_cast<DzFacetMesh*>(shape->getGeometry());
// should check the mesh for null first.
for(int i = 0; i < mesh->getNumMaterialGroups(); i++)
DzMaterialFaceGroup* materialGroup = mesh->getMaterialGroup(i);
QString name = materialGroup->getName();
// or take a look at DzFacetMesh::findMaterialGroup