50 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [ Noy. 24, 
more to the very remarkable fact, that, so far as the present evi- 
dence goes, the dry land of those Triassic epochs was as extensive in 
the old and northern New World as itis at the present day, and that, 
just as the mammalian and ornithic faune of these regions lead 
us to group North America, Europe, Asia, and South Africa m one 
vast Arctogeal 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. 
Puate I. 
Fig. 1. The skull of Hypsilophodon Foxit, of the natural size. 
Pa, parietal; Fr, frontal; Na, nasal; Pm, premaxilla; La, lacrymal ; 
Mn, mandible; a, prelacrymal vacuity ; 6, suture between the premax- 
illary and maxillary bones; NV, nasal aperture ; c, centrum of a vertebra. 
2. A molar tooth, and 
3. An incisor tooth, magnified. 
4, The left ramus of the mandible: Qw, the quadrate bone; @, the coro- 
noid process. 
5. The left premaxilla. In this figure and im fig. 1. the line from Pmex 
leads to the edentulous prolongation. 
6. Side view of a caudal vertebra, of the size of nature. 
7. End view of another caudal vertebra. 
8. A chevron bone, of the natural size. 
Plate IL. 
The pelvis of Hypsilophodon Foxti, two-thirds the natural size. 
a, the anterior, 6. the posterior extremity of the right ilium ; Js. Js. 
the right and left ischia ; Pe. the pubis. 
Prats EIT. 
Fig. 1. The dentary portion of the left ramus of the mandible of Thecodon- 
tosaurus. 
2. One of the teeth of Thecodontosaurus, magnified three times. 
3. The typical specimen of the tooth of Paleosaurus cylindrodon, magni- 
fied three times. 
4. One of the teeth of the Warwickshire Palgosaurus. 
5. A caudal vertebra of Thecodontosaurus (?) with its chevron bone, which 
is imperfect below. 
6. The anterior aspect of the same chevron bone. 
7. The inner face of the right ilium of Thecodontosaurus (?). 
8. The proximal end of the right tibia of Thecodontosaurus. 
9. The three sacral vertebra from the Warwickshire Trias. 
0. End view of the anterior vertebra of the sacral series (fig. 9). 
1. A. anterior view, B. lateral view, of the tooth from the Warwickshire 
Trias which probably belongs to Teratosaurus. 
— 
Discussion. 
Sir Ropertck Murcurson, who had taken the Chair, inquired as 
to the lowest formation in which the bird-like character of Dino- 
saurians was apparent, and was informed that it was to be recog- 
nized as low as the Trias, if not lower. 
Mr. Srexry 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 had come to conclusions as to 
the grouping and classification of Saurians somewhat different from 
