Multiple classes in a module ok?

Can you specify multiple classes in a module? If so, how do
you reference them individually after a requires() invocation?

--- modules/animals.js ---

class Animal { }
class Dog extends Animal { }
class Cat extends Animal { }

exports = Dog, Cat;

var animals = require("animals");

var d = new Dog();
var c = new Cat();

Uncaught ReferenceError: "Dog" is not defined
at line 2 col 5
var d=new Dog();

Uncaught ReferenceError: "Cat" is not defined
at line 3 col 5
var c=new Cat();