order:

Testudines

Turtles and Tortoises

Links to families I've seen:

Carettochelyidae Pignose Turtles	Emydidae Box and Pond Turtles
Cheloniidae Sea Turtles	Kinosternidae American Mud and Musk Turtles
Cheluidae Side-necked Freshwater Turtles	Pelomedusidae Afro-American Sideneck Turtles
Chelydridae Snapping Turtles	Platysternidae Bighead Turtles
Dermatemydidae River Turtles	Testudinidae Tortoises
Dermochelyidae Leatherback Turtles	Trionychidae Softshells