What is the classification of a dinner plate jelly?

"Dinner plate jelly" is not a recognized classification of jellyfish. It's likely a colloquial term used to describe a large jellyfish, perhaps one with a bell that resembles a dinner plate in size or shape.

There are many large jellyfish species, but without more information it's impossible to say which one is being referred to.

To get a more precise answer, it would be helpful to know:

* Where was the jelly seen? Location can help narrow down the possibilities.

* What was its approximate size? A specific diameter would be helpful.

* What did it look like? Did it have any distinctive features, such as tentacles, color, or shape?

Once you have more information, you can search for jellyfish species that match the description or consult an expert for identification.