With his finances improved , he was able to publish a massive work on the Batrachians of North America , which was the most detailed work on the continent 's frogs and amphibians ever done , p350 and the 1,115-page The Crocodilians , Lizards and Snakes of North America . With his finances improved , he was able to publish a massive work on the Batrachians of North America , which was the most detailed analysis and organization of the continent 's frogs and amphibians ever mastered , and the 1,115-page The Crocodilians Lizards and Snakes of North America .