(_a_) The nostrils.
(_b_) The eyes.
(_c_) The nictitating membrane and a short tentacle beneath the eye.
[_The tentacle is absent in the Frog._]
(_d_) The tympanic membrane, which is not shown in the Platana, but
is well marked in the Frog.
(_e_) The opening of the cloaca.
(_f_) The limbs and their divisions.
(_g_) The skin with tube-like lines round the body. [_In the Frog
these lines are not present._]
[Illustration: FIG. 1.--Xenopus lævis and Rana fuscigula.]