#giant seashell

Screencaps taken from wiki articles.

The Little Mermaid (character)

I've already discussed what I suspect is the reasoning behind Attina's design. To summarize, her crown resembles that of the Statue of Liberty, and the Colossus of Rhodes--the latter of which is Helos, the Greek God of the Sun, explaining her red and orange color scheme.

But what exactly is that spiky tiara made out of?

There are a few possibilities.

Rankin Bass's "The Daydreamer" (1966)

The Little Mermaid's castle is a gorgeous set design for one segment in a TV special. And they didn't have Disney's "Little Mermaid" yet to compete with.

The last shot is actually Hans abd the mermaid sliding down a giant seashell, outside the palace.