Page:Quarterly Journal of the Geological Society of London, vol. 26.djvu/119

1869.] tures far surpassing in size the largest of existing reptiles, will, it is presumed, be deemed sufficient ground for establishing a distinct tribe, or suborder, of Saurian reptiles, for which I would propose the name of Dinosauria.

"Of this tribe the principal and best-established genera are the Megalosaurus, the Hylæosaurus, and the Iguanodon, the gigantic crocodile lizards of the dry land, the peculiarities of the osteological structure of which distinguish them as clearly from the modern terrestrial and amphibious Sauria as the opposite modifications for an aquatic life characterize the extinct Enaliosauria, or marine lizards".

Further on it is stated that "the Reptilian type of structure made the nearest approach to mammals" in the Dinosauria (l. c. p. 202).

Every character which is here added to Von Meyer's diagnosis and description of his Pachypoda has failed to stand the test of critical investigation; while it is to birds and not to mammals that the Dinosauria approach so closely. There is, in fact, not a single specially mammalian feature in their whole organization.

Even in point of etymological appropriateness, the term "Dinosauria" is no more fitting for reptiles of which some are small, than "Pachypoda" is for reptiles of which some have slender feet; but as Von Meyer's name has never obtained much currency, it may be well to allow justice to give way to expediency, and to retain the name of Dinosauria for those reptiles which agree in all the most important and characteristic parts of their structure with Megalosaurus and Iguanodon.

The group thus limited is susceptible of very clear diagnosis from all other reptiles, inasmuch as its members present the following combination of characters:—

1. The dorsal vertebræ have amphicœlous or opisthocœlous centra. They are provided with capitular and tubercular transverse processes, the latter being much the longer.

2. The number of the vertebræ which enter into the sacrum does not fall below two, and may be as many as six.

3. The chevron bones are attached intervertebrally, and their rami are united at their vertebral ends by a bar of bone.

4. The anterior vertebral ribs have distinct capitula and tubercula.

5. The skull is modelled upon the Lacertilian, not on the Crocodilian type. There is a bony sclerotic ring.

6. The teeth are not ankylosed to the jaws, and may be lodged in distinct sockets. They appear to be present only in the præmaxillæ, maxillæ, and dentary portions of the mandible.

7. The scapula is vertically elongated; the coracoid is short, and has a rounded and undivided margin. There is no clavicle.

8. The crest of the ilium is prolonged both in front of and behind the acetabulum; and the part which roofs over the latter cavity forms a wide arch, the inner wall of the acetabulum having been formed by membrane, as in birds.

9. The ischium and pubis are much elongated.

10. The femur has a strong inner trochanter; and there is a crest