My father used to own a very early copy of Carta Marina (hey, Olaus Magnus was Swedish and plain old Olof Magnusson before he became a scholar). He gave it to grandpa who put it up in his study. I used to play in that study when I visited my grandma 'coz it had all of grandpa's cool old stuff in it. I remember looking at the map and making up stories.
Olaus Magnus' "History of the Northern Peoples" is a hoot, its like a later and more mild-mannnered down-to-earth John Mandeville - about the place where I live.
I'd love to read about the early zoology stuff from that time. I managed to read some of "Of monsters and Marvels" the other day, it's very charming how they used to include elephants and ostritch as "monsters".
They had a version of Magnus' work in Swedish at our high school library. It is technically a work of cultural history but dips into nature studies when necessary or the author feel like it. For instance, Magnus has some interesting stuff on the (then) current werewolf problem in Latvia, comparing it to famous werewolf reports from antiquity. (Among other things, the werewolves keep drinking all the beer!)
I had hoped to find some online version of it and show you a link (its not like there're copyright issues) but no such luck. There is an English translation as well but presumably the translators have some rights to it.
well, this one is based on a copy of the Carta Marina that is acessible on wikipedia. Most of the reported sea serpents I got from "In the wake of sea serpents" and "There are giants in the sea", both full of sightings. The mythical stuff is mainly from wikipedia.