112 R. Lydekker—Tertiary Lacertilia and Ophidia. 
Kocene genera Saniva, Leidy, and Glyptosaurus, Marsh, are in all 
probability closely related to Placosaurus. 
Paleryx and Paleopython.—The genus Paleryx was founded in 
1850 by Sir R. Owen’ on the vertebrae of a comparatively large 
snake from the Hordwell Beds, which was regarded as nearly allied 
to the existing genus Hryxz. In 1880 M. Rochebrune? described and 
figured certain Ophidian vertebra from the Querey Phosphorites 
under the new generic title of Palgzopython; identifying one species 
with Python cadurcensis of Dr. Filhol,* and naming a second species 
Paléopython Filholi. On comparing vertebrae from Quercy in the 
Museum (No. R. 428, a) which are indistinguishable from the speci- 
men figured by Rochebrune as Palgopython cadurcensis with the type 
vertebra of Paleryx rhombifer (No. 25259), I find that the two cannot 
be even specifically distinguished. Similarly I find that smaller 
vertebree from Quercy (No. R. 428, p) agree precisely with the types 
(No. 25261) of the Hordwell Paleryx depressus, Owen; and I believe 
that these are in all probability specifically identical with slightly 
larger Quercy vertebree (No. R. 428, c), agreeing with the type of 
Paleopython Filholi, Rochebrune. It appears, therefore, that the genus 
Palgopython is identical with Paleryx, and should accordingly be 
abolished ; but Iagree with M. Rochebrune in regarding the vertebree 
to which this name was applied as indicating a Snake very closely 
allied to Python, and clearly referable to the same family. 
Palezophis.—The vertebree of huge Serpents from the London and 
Bracklesham Clays, described by Sir Richard Owen in the memoir 
above cited as Palwophis, were regarded by him as allied to the 
marine Hydrophide. Other vertebre of similar structure were 
subsequently obtained from marine Eocene beds in North America, 
and described by Prof. Marsh under the name of Titanophis 
(Dinophis), although regarded by Prof. Cope as generically indis- 
tinguishable from Paleophis. Both these writers suggested that 
these Serpents were more nearly allied to the Pythonide than to the 
Hydrophide ; and in the memoir which I have already quoted M. 
Rochebrune came to the conclusion that they should be included in 
the Pythonide. If, however, the vertebre of Palzophis be compared 
with those of Python, it will be seen that they differ by their much 
taller neural spine, by the lower position and different contour of 
the costal articulation, by the much less prominent zygapophyses, 
by the more developed heemal carina, as well as in several minor 
features; and it would thus appear that on osteological grounds 
alone the reference to the Pythonide cannot be maintained. This 
inference is, however, supported by other considerations. Thus the 
existing Pythons are confined to the Old World and Australia ; and, 
although they can and do swim well in freshwaters, they are 
essentially land snakes. Judging, however, from the strata in 
which Palgophis and Titanophis occur, there is a very strong pre- 
sumption, as Sir R. Owen and Prof. Marsh have pointed out, that 
1 Reptilia of London Clay (Mon. Pal. Soc.), pt. 3, p. 67. 
2 Nouv. Archiv. d. Muséum, ser. 2, vol. iii. p. 277, pl. xix. 
3 Ann. Sci. Géol. vol. viii. p. 270 (1877). 
