I thought this was quite a good fit for spooky season. If you’re like me, you’ll read it through the first time then, taking into consideration the editor’s comment at the end, you’ll read it again from a new (and macabre) perspective. It was taken from the October 9, 1909 issue of The Country-Side.
The book mentioned, A Description of 300 Animals, was an 18th century educational book intended for children and can be viewed at Google Books. Unfortunately it does not contain any chapter called “Fabulous Animals” like the edition noted in the letter. It is copiously illustrated and while there are no mermaids, there are six breeds of dogs, which I hope will be of interest: