In the Rhamphorhynchæ at present there appears to be but one genus known:
Rhamphorhynchus (von Meyer). The nares and middle holes are both small, ovate, of nearly equal size, and close together at the side of the head in front of the orbit.
In the Dimorphodontæ the only genus is
Dimorphodon (Owen). It has the nares enormously large. The middle holes are also large.
In the Ornithocheiræ the genus is
Ornithocheirus (Seeley), in which teeth are prolonged anterior to the muzzle, and the palate has a longitudinal ridge.
With the osteological illustrations of the Ornithosauria are arranged some premaxillary bones, which show varieties of form of the snout. These variations of shape serve easily to indicate different species. And the following memoranda from those specimens and other specimens in the drawers form a synopsis of the species of the Cambridge genera, which may hereafter be fully elucidated from the copious materials in the series of associated remains.
I.
| Case. | Comp. | Tablet. | Specimen. |
| J | c | 13 | 2 |