river-horse—the hippopotamus:
- The crocodiles and riverhorses are common in this unpeopled region; and I often looked upon them with terror.
sea-horse—
1. the walrus:
- From this account the horse-whale seems to have been the animal now called the walrus, or seahorse, whose tusks are ivory.
2. (pl.) white foam and spray on the crests of waves:
- The sea was a beautiful deep blue, as calm as could be with little white sea horses here and there.
3. (also: flying sea-horse) a fish of peculiar form, with body somewhat like a horse’s head:
- The sea horse is a very strange fish that lives in warm water.