"The Coming Race", Chapter XVIII, by Edward Bulwer-Lytton

copse: a small group of trees

The picture used is "Spinosaurus 2020" by FredtheDinosaurman, used here under the Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported license (https://creativecommons.org/licenses/by-nc-nd/3.0/).

I assume the krek-a must be dinosaurs, if they are giant reptiles that pre-date humans. And it is a common trope for dinosaurs to still exist in lost lands like this. While it is a matter of some debate, the Spinosaur is thought by many to be a good swimmer, and it is definitely a carnivore, so there you go.

To follow along: https://www.gutenberg.org/files/1951/1951-h/1951-h.htm#link2HCH0018