Each of the first two has a bony prepollex, rugose skin on the dorsum, and heavy body.
"A Review of the Middle American Tree Frogs of the Genus Ptychohyla"
William E. Duellman
Each of the last two has a bony prepollex, rather rugose skin on the dorsum, and more squat body.
"A Review of the Middle American Tree Frogs of the Genus Ptychohyla"
William E. Duellman
Sometimes the pileus is rugose on the center.
"Studies of American Fungi. Mushrooms, Edible, Poisonous, etc."
George Francis Atkinson