  A complete and harmonized fundamental circuit relational graph with four
linear and four memory elements is constructed based on newly defined elements,
which provides a guide to developing novel circuit functionalities in the
future. In addition to resistor, capacitor and inductor which are defined in
terms of a linear relationship between the charge q, the current i, the voltage
v, and the magnetic flux, Chua proposed in 1971 the fourth linear circuit
element to directly relate magnetic flux and charge. A non-linear resistive
device defined in memory i-v relation and dubbed memristor, was later
attributed to such an element and has been realized in various material
structures. Here we clarify that the memristor is not the true fourth
fundamental circuit element but the memory extension to the concept of
resistor, in analogy to the extension of memcapacitor to capacitor and
meminductor to inductor. Instead, a two-terminal device employing the linear
magnetoelectric effects, termed transtor, possesses the function of relating
directly flux and charge and should take the position of the fourth linear
element. Moreover, its memory extension, termed memtranstor, is proposed and
analyzed here.
