These chimeras eat what they please,
Mostly crustaceans, but not cheese;
They don’t live in a sewer,
And the casual viewer
Can see that they don’t carry fleas.
See also this limerick’s Fishy Names companion pieces:
The spotted ratfish is a resident of the northeastern Pacific. Like sharks, it is a cartilaginous fish. It gets its name from its distinctive pointed rat-like tail. A mostly nocturnal, shallow-water forager, ratfish are partial to crabs, clams, shrimp, worms, small fish and starfish. It possesses a venomous dorsal fin spine that can inflict a painful, mildly toxic wound to humans.