Because this sentence makes a statement, a period is the appropriate endmark.

Where's Professor Snape? shouted a girl from the Slytherin table. He has, to use the common phrase, done a bunk, replied Professor McGonagall, and a great cheer erupted from the Gryffindors, Hufflepuffs, and Ravenclaws.

This seemed to be an inexpugnable refuge, where we could live untroubled and learn to know each other."

After the completion of copulation, the number of eupyrene sperm bundles in a spermatophore gradually decreased.