more to the very remarkable fact, that, so far as the present evidence goes, the dry land of those Triassic epochs was as extensive in the old and northern New World as it is at the present day, and that, just as the mammalian and ornithic faunæ of these regions lead us to group North America, Europe, Asia, and South Africa in one vast Arctogæal province, so the affinities of the land reptiles of the Trias lead to the conclusion that at that epoch the same regions constituted a similar great distributional area.
EXPLANATION OF PLATES I-III.
Plate I. | |
| Fig. 1. | The skull of Hypsilophodon Foxii, of the natural size. Pa, parietal; Fr, frontal; Na, nasal; Pmx, præmaxilla; La, lacrymal; Mn, mandible; a, prælacrymal vacuity; b, suture between the præmaxillary and maxillary bones; N, nasal aperture; c, centrum of a vertebra.
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| 2. | A molar tooth, and
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| 3. | An incisor tooth, magnified.
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| 4. | The left ramus of the mandible: Qu, the quadrate bone; a, the coronoid process.
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| 5. | The left præmaxilla. In this figure and in fig. 1. the line from Pmx leads to the edentulous prolongation.
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| 6. | Side view of a caudal vertebra, of the size of nature.
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| 7. | End view of another caudal vertebra.
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| 8. | A chevron bone, of the natural size.
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Plate II. | |
The pelvis of Hypsilophodon Foxii, two-thirds the natural size. a, the anterior, b. the posterior extremity of the right ilium; Is. Is. the right and left ischia; Pb. the pubis.
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Plate III. | |
| Fig. 1. | The dentary portion of the left ramus of the mandible of Thecodontosaurus.
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| 2. | One of the teeth of Thecodontosaurus, magnified three times.
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| 3. | The typical specimen of the tooth of Palæosaurus cylindrodon, magnified three times.
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| 4. | One of the teeth of the Warwickshire Palæosaurus.
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| 5. | A caudal vertebra of Thecodontosaurus (?) with its chevron bone, which is imperfect below.
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| 6. | The anterior aspect of the same chevron bone.
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| 7. | The anterior aspect of the same chevron bone.
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| 8. | The proximal end of the right tibia of Thecodontosaurus.
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| 9. | The three sacral vertebræ from the Warwickshire Trias.
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| 10. | End view of the anterior vertebra of the sacral series (fig. 9).
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| 11. | A. anterior view, B. lateral view, of the tooth from the Warwickshire Trias which probably belongs to Teratosaurus.
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Discussion.
Sir Roderick Murchison, who had taken the Chair, inquired as to the lowest formation in which the bird-like character of Dinosaurians was apparent, and was informed that it was to be recognized as low as the Trias, if not lower.
Mr. Seeley insisted on the necessity of defining the common plan both of the Reptilia and of the ordinal groups before they could be treated of in classification. He bad come to conclusions as to the grouping and classification of Saurians somewhat different from
