  The masses of tetraquark states of all $qc\bar q \bar c$ and $cc\bar c \bar
c$ quark configurations are evaluated in a constituent quark model, where the
Cornell-like potential and one-gluon exchange spin-spin coupling are employed.
All model parameters are predetermined by comparing the theoretical and
experimental masses of light, charmed and bottom mesons. The theoretical
predictions of the charmoniumlike tetraquarks are compared with the observed
$XYZ$ states, and one tentative assignment is suggested. The work suggests that
the $X(6900)$ observed by LHCb is likely to be the first radial excited
fully-charm tetraquark state with $J^{PC} = 1^{+-}$ in the $\bar 3_c \otimes
3_c$ configuration, and the ground and second radial excited states of
fully-charm tetraquark are around $6494$ and $7253$ MeV respectively.
