  We derive some localization and perturbation results for coneigenvalues of
quaternion matrices. In localization results, we derive Ger\v{s}gorin type
theorems for right and left coneigenvalues of quaternion matrices. We prove
that certain coneigenvalues lie in the union of Ger\v{s}gorin balls, in
contrast to the complex situation where all eigenvalues lie in the union of
Ger\v{s}gorin discs. In perturbation results, we derive a result analogous to
the Hoffman-Wielandt inequality for basal right coneigenvalues of conjugate
normal quaternion matrices. Results analogous to the Bauer-Fike theorem and a
generalization of the Hoffman-Wielandt inequality are discussed for basal right
coneigenvalues of condiagonalizable quaternion matrices. Finally, we define
spectral variation and Hausdorff distance between right (con)eigenvalues of two
quaternion matrices and obtain bounds on them.
