1891.] Remarks on Reptiles Called Dinosauria. 453 
to expect ‘to find impressions of a tail, with the impressions pro- 
duced by the hind limbs, but this we do not. The impressions, 
therefore, seem to be produced by an animal having a short tail. 
Some characters of birds remind us of the Megalosauria; but 
the fact remains that we know hardly anything about the actual 
ancestors of this branch of the Monocondylia. The birds have a 
well-ossified alisphenoid, no epipterygoid, and there seems to be 
little doubt that the avian ancestors of the birds of to-day had 
already this character; but the ancestors of these must have had 
the brain-case open in front, no ossified alisphenoids, but an 
epipterygoid ; and here, again, we reach a form like the Progano- 
sauria and Rhynchocephalia. 
Clark University, Worcester, Mass., Feb. 11th, 1891. 
AUTHORITIES CITED. 
1. OWEN, R.—Report on British Fossil Reptiles. Brit. Asso. Rep., Lon- 
don, 1840, pp. 102, 103. 
2+ MEYER, H. v.—Uber fossile Saurier. Isis, 1830, pp. 517-519. Also 
in his Palaeologica zur Geschichte der Erde und ihrer Geschopfe. Frankfurt, 
a. M., 1832, p. 201. 
3. KAUP, J. J.—Das Thierreich in seinen Hauptformen systematisch 
qeschrieben. Vol. II., Part 2, p. 18, Darmstadt, 1836. 
4. FITZINGER, LEOPOLDUS. Bere Reptilium. Fasciculus Primus: 
Amblyglossæ. Vindobonæ, 1843, p. 1 i 
_ 5« MEYER, H. y, —System der eid Saurier. Neues ‘Jahrb. Min., 
1845, pp. 278-285. 
6. GERVAIS, P.—Observations Psat ap aux reptiles fossiles de la Fr rance, 
Paris, Compt. Rend., XXXVI., 1853, P- 
7- OWEN, R.—On the Anatomy of vad Vol. I., London, pp. 
14-18. 
8. HAECKEL, Ernst.—Generelle Morphologie der Organismen. Berlin, 
1866, Bd. H. , p. 136. 
9. COPE, E. D.—Synopsis of the Extinct Batrachia, Reptilia, and Aves of 
North Aunérka. Trans. Amer. Philos. Soc., Vol. XIV.. 1870, p- 9°, 99- 
HuxLey, T. H.—An Introduction to the Classification of Animals. 
ndon, 1869, pp. 110-111. 
oe sabe "D .—Synopsis of the Extinct Batrachia and Reptilia of 
North America. Trans. Amer. Philos. Soc., Phila., 1870, pp- 26-53- 
12. HuxLey, T. H.—On the Classification of the Dinosauria, with Obser- 
Vations on the Dinosauria of the Trias. Q. J. G. S» Vol. XXVI., pp. 32-36. 
