Question

structures are similar in appearance but not in structure
analogous structures
homologous
vestigial
embryonic

Explanation:

Analogous structures have similar functions and appearances due to convergent evolution, but different underlying structures. Homologous structures have similar underlying structures from a common ancestor despite different functions or appearances. Vestigial structures are remnants with little or no function. Embryonic structures refer to those in the embryonic stage. The description "similar in appearance but not in structure" fits analogous structures.

Answer:

Analogous Structures