[Footnote AA: So far as can be judged from figures, it appears to have but three bones in the wing-finger: what Cuvier regarded as a terminal and fourth joint, the bone _n_, Pl. XXIII. fig. 7, _Oss. Foss._, appearing to me to be the fibula of the tibia marked _e_. _s_ in the same figure would be the terminal phalange, and _r_ the first phalange, as may be proved by measuring them with those of the other hand, so that a phalange is missing from between them. Both the terminal phalanges appear to be hooked at the termination. Goldfuss figures the phalanges so as to make the bone which appears to be fibula in Sömmerring and Cuvier look like a fourth phalange.] _Pachyrhamphus_ (Fitzinger). The nares are entirely separated from the middle holes of the head; both are large. The head is thick and massive. The prepubic bones meet mesially. No evidence of the number of phalanges in the wing-finger. The quadrate bone is massive, but has small attachment to the skull. Two sacral vertebræ. Wing-metacarpal very short. The type is P. crassirostris (Goldfuss). _Cycnorhamphus_ (Seeley). Nares very small, looking upward from a swan-like beak. The middle hole of the skull very large and elongated and lateral. Neck long. Wing-metacarpal long. Four joints in the wing-finger. Ilium widening in front. Epipubic bones meeting mesially. The type is Pterodactylus suevicus (Quenstedt). 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. Ornithocheirus Sedgwicki (Owen). Case. Comp. Tablet. Specimen. =J= _c_ 13 2