The Golden Age Comic Book Stories blog has a great set of illustrations from "The Interstellar Zoo", found in the 1951 short story collection Travelers of Space. The aliens were drawn by Edd Cartier, who was a regular illustrator of the science fiction pulps. Cartier also illustrated the cover of the anthology (shown at right).
His distinctive style is iconic of the Golden Age of science fiction. Go check out all the images.
(Thanks for the tip Bri!)