l. Side View of the head of an Ichthyosaurus, marking by corresponding letters, the analogies to Cuvier's figures of the same bones in the head of the Crocodile. (Conybeare.)

2. Posterior part of a lower jaw of Ichthyosaurus cornmunis, in the Oxford Museum. (Conybeare.)

3-7. Sections presented by the component bones of Fig. 2 in fractured parts above each section. (Conybeare.)

8. View of the lower Jaw of Ichthyosaurus seen from [024] beneath, exhibiting thc course of its over lapping bones. (Conybeare.)

A. Tooth of a Crocodile, shcwing the incipient absorption of the hollow cone which forms its base, from the effect of pressure of a new tooth rising beneath. (Conybeare.)

B. Similar effects shewn in the transverse section of the upper and lower jaws of an Ichthyosaurus. (Cuvier.)

C. Example of the same kind of absorption produced by the pressure of a new tooth, on the base of an older tooth in the jaw of lchthyosaurus. (Conybeare.)