np = pthi - ptlo + 1;
kk = (np-1)/2;
selecti(kk,ptindx,ptlo,np,coords,tdim*npts);
// XXX = change to copyAssign
hi.copyAssign(boxes[tmom].hi);
lo.copyAssign(boxes[tmom].lo);
hi.x[tdim] = lo.x[tdim] = coords[tdim*npts + ptindx[ptlo+kk]];
boxes[++jbox] = new Boxnode(boxes[tmom].lo,hi,tmom,0,0,ptlo,ptlo+kk);
boxes[++jbox] = new Boxnode(lo,boxes[tmom].hi,tmom,0,0,ptlo+kk+1,pthi);