and teeth with those of Bats (Pl. 21, and Pl. 22, M.) shows that the fossil animals in question cannot be referred to that family of flying Mammalia.
The vertebræ of the neck are much elongated, and are six or seven only in number, whereas they vary from nine to twenty-three in birds.[1] In birds the vertebræ of the back also vary from seven to eleven, whilst in the Pterodactyles there are nearly twenty; the ribs of the Pterodactyles are thin and thread-shaped, like those of Lizards, those of birds are flat and broad, with a still broader recurrent apophysis, peculiar to them. In the foot of birds, the metatarsal bones are consolidated into one: in the Pterodactyles all the metatarsal bones are distinct; the bones of the pelvis also differ widely from those of a bird, and resemble those of a Lizard; all these points of agreement, with the type of Lizards, and of difference from the character of birds, leave no doubt as to the place in which the Pterodactyles must be ranged, among the Lizards, notwithstanding the approximation which the possession of wings seems to give them to Birds or Bats.
The number and proportions of the bones in the fingers
and toes in the Pterodactyle, require to be examined in some
air, or become an instrument of true flight, like the arm or wing of Birds and Bats; the arm or fore leg of the Draco volans differs not from that of common Lizards.
- ↑ In one species of Pterodactyle, viz. the P. macronyx, Geol. Trans. N. s. V. iii. pl. 27, page 220, from the lias at Lyme Regis, there is an unusual provision for giving support and movement to a large head at the extremity of a long neck, by the occurrence of bony tendons running parallel to the cervical vertebræ, like the tendons that pass along the back of the Pigmy Musk (Moschus pigmæus,) and of many birds. This provision does not occur in any modern Lizards, whose necks are short, and require no such aid to support the head. In the compensation which these tendons afforded for the weakness arising from the elongation of the neck, we have an example of the same mechanism in an extinct order of the most antient reptiles, which is still applied to strengthen other parts of the vertebral column, in a few existing species of mammalia and birds.
