FOSSIL VARANIDAE AND MEGALANIDAE. 
435 
originate directly from Aigialosaurs. Thus, though differing in 
questions of detail, Boulenger, Baur and Nopcsa all conclude to a very 
close connexion existing between the Mosasaurian 
group and the family Varanidae. Boulenger and Nopcsa placed their 
origin in the suborder Platynota, whilst Baur classified the Mosasauria 
systematically under the name of « Mosasauridae », as a family, 
in the suborder Platynota. 
In opposition to this opinion Osborn 1 after narrow examination of 
the case deems that the great osteological differences «do not justify the 
assertion that Varanidae and Mosasaurs sprang from a common stem». 
The only conclusion we are absolutely warranted in drawing is the follo¬ 
wing (p. 188): «The Mosas aurs are a very ancient marine offshoot of the 
Lacertilia presenting a few resemblances in the skull to the* Varanoids . . .» 
In his excellent work Fürbringer 2 also shares in Osborn's view as to 
the chief points in writing as follows : «Auf Grund eigener Beobachtungen 
stimme ich Baur, Dollo u. A. hinsichtlich der Zugehörigkeit zu den La¬ 
certilia bei ; möchte aber angesichts der von Williston und Osborn hervor¬ 
gehobenen Verhältnisse die Subordo Platynota Baur’s oder die intimen 
Verwandtschaften zu den Varaniden nicht aufrecht erhalten.» According 
to this, Fürbringer excludes Mosasauria from Baur’s suborder Platynota - 
regarding the former as constituting an independent suborder, — Fürbrin- 
ger’s system would therefore result, after the exclusion of Helodermatidae , 
in the suborder Platynota consisting only more of the gentes Dolichosauro- 
morpha and Varanomorpha. 
As far as I was able to gain an insight in the Mosasauria-qvLestion, 
in its essential points, Falso adopt Osborn and Fürbringer’s opinion, from 
my present experiences judging as an impossibility the descent 
of Mosasauria from the Aigialosauridae . The osteological characters of 
Mosasauria present such a far reaching specialization, 
that in first instance I must doubt of so striking a transfor¬ 
mation taking place in compariti vely so short a time 
as, considering the. geological appearance of the two groups, Xopcsa’s 
theory would imply, all the less as I find such morphological 
differences in Mosasauria which, considering the circumstance 
mentioned, to. my mind, could hardly permit their ortho- 
genetical descent being traced to the Aigialosauridae. The 
Mos a s a u r skull doubtless offers much resemblance to the afore 
1 A Compì. Mosasaur Skeleton &c., Mem. Amer. Mus. Nat. Hist., Vol. I, 1893 — 1903 
New York, 1903, p. 187. 
2 Op. cit. p. 616. 
28* 
