P. regius = P. sebae, [601];

P. reticulatus, [598];

P. spilotes, [598], [599]

Pythoninae, [598] f.

Pythonomorpha, [487] f.

Pyxis arachnoides, [365]

Radde's "law of the steppe," [493]

Rana, [241], [249] f.;

sacral vertebrae, [22];

shoulder-girdle, [25];