Here's why:
* "Greyfriars Bobby was a Skye Terrier" is a declarative sentence that states a fact.
* It uses the linking verb "was" to connect the subject ("Greyfriars Bobby") to the predicate ("a Skye Terrier").
* Linking verbs don't take direct objects, so the sentence is neither transitive nor intransitive.
Transitive verbs require a direct object to receive the action (e.g., "He threw the ball.").
Intransitive verbs do not take a direct object (e.g., "The dog ran.").