FOSSIL VARANIDAE AND MEGALANIDAE. 
441 
A descent of the Snakes from the Dolichosauridae is, to my mind, 
impossible as well for biological as for morphological reasons. 
Taking all considerations into account, both these could be summed up 
as follows : the Dolichosauridae and Snakes present no trace of 
common morphological characters whence an evolution of the latter 
from Dolichosaurs could reasonably be inferred, whilst, on the 
other hand, the geological occurrence of Dolichosaurs and 
Snakes, to my mind, furnishes no sufficient biological base to the 
supposition that heterogeneous groups as the two above named, 
could have evolved one from the other. I shall not enter here into more 
detailed discussions about my opinion as exposed above, my chief endea¬ 
vour being an atteint to prove the absolute improbability, as also re¬ 
corded b y Janensch (op. cit.), of an orthogenet ical relation 
of the Varanidae (or the Platynots in general) and the Mosa - 
sauria with the Ojphidia , which w T ith respect to p h y le¬ 
ticai parentage bear no intimate relation to 
ea cho + h er. 
In the following I give some schemes representing the different genea¬ 
logical graphicons with regard to descent and relation of Varanidae after 
Boulenger, Nopcsa and myself, the last of these constructed on base 
of Osborn’s respectively Fürbringer’s theories. 1 
LACERTI Lî R 
PYTHONOMORPHA (VARANIDAE) 0PHID1A 
Geneology after Boulenger (op. cit.). 
1 Upon this question Fürbringer writes as follows (op. cit. p. 620): «Der Super- 
ordo St re ptostylica (Squamata, Lepidosauria ) besteht aus den beiden Ordnun¬ 
gen der La ce rtilia und Op hi dia, von denen die erstere die vielgestaltigste 
ist und zugleich die primitiveren Formen enthält, während aie letztere (die hier nicht 
weiter behandelt wird) einen einseitig und relativ höher entwickelten Zweig darstellt». 
I find this interpretation, based on close investigations, as thoroughly natural, and fully 
agree with Fürbringer on the subject. 
