Prehistoric species of various eras featured in the series include Agriochoerus, Alamosaurus, Archaeotherium, Brontops, Camptosaurus, Columbian mammoth, Coryphodon, Deinosuchus, Diprotodon, Eurypterid, Gastornis (called Diatryma), Gorgosaurus, Hoplophoneus, Hyaenodon, Ichthyostega, Mastodon, Megalania, Merycoidodon, Metamynodon, Metoposaurus, Mylodon, Ornithomimus, Parasaurolophus, Phenacodus, Placerias, Postosuchus, Procoptodon, Rutiodon, Saurophaganax or Allosaurus (referred to as Epanterias), Stegosaurus, Teratosaurus, Triceratops, Troodon formosus (presented as Stenonychosaurus, and supposedly a type of pachycephalosaur), and Tyrannosaurus trionychus.

Tyrannosaurs of the genus Gorgosaurus are mentioned occasionally, and many times Reginald Rivers will say that the Raja is out in some period in the Cenozoic, taking a group to hunt some form of prehistoric mammal such as titanothere, entelodont, or uintathere.

Dated material includes the following: A tenth story of Reginald Rivers, "Gun, Not for Dinosaur", authored by Chris Bunch,[2] appeared in Harry Turtledove's 2005 tribute anthology honoring L. Sprague de Camp, The Enchanter Completed.

This story contains elements of scientific racism and white supremacism as Rivers' client, a racist Texas millionaire, and his two Boer bodyguards attempt to prevent the evolution of Negroes by going back in time in Africa to kill their prehistoric ancestors.

She gives the collection a three star rating, deeming it "lightweight, amusing work ... very well done candy, with a little paleontological education thrown in," and "particularly sharp shots at fundamentalists and animal-rights activists."