Cumacea
(cumaceans)
Cumaceans are common to estuaries and the lower reaches of maritime streams and rivers. They are distinctive with a broad, circular or oval carapace covering the front of the body, and a very long, thin abdomen that ends in a forked tail.

Mysidacea
(opposum shrimp) look a lot like shrimp but have more than 10 major legs, are smaller, and don't have a prominent rostrum or ridge extending forward from the top of their head.