EF. Thurlow Leeds—On Metriorhynchus. 315 
In view of the fact, therefore, that English paleontologists have 
identified the common species of Crocodile from Fletton, near Peter- 
borough, with JL superciliosus, it seems to have been an entirely 
superfluous and unwarranted proceeding on the part of Dr. E. Schmidt 
to have given a new name to the species, viz. If. Jackel,’ especially 
as he has evidently based his species on the one specimen in the 
Berlin Museum, and at the same time adduces no reasons for his 
action. Dr. Schmidt is only adding another synonym to a list that is. 
already long enough. 
Dr. G. von Arthaber, in the monograph he has lately published,? 
tries to discover the reasons which led Dr. Schmidt to create a new 
species, and lays great stress on the shape of frontals and prefrontals 
and the amount and nature of the conjunction of these bones with 
one another. He denies that it can be IL. superciliosus on account of 
‘‘ the laterally strongly prominent and anteriorly pointed preefrontals”’ 
(‘‘den seitlich stark vorspringenden und gegen vorn spitz zulaufenden 
Prifrontialien”’) which this species possesses. If there is one 
characteristic which could be applied absolutely literally to the 
Fletton species it is this one, and one which all the skulls of the 
common JMMetriorhynchus from the Peterborough district show.* 
Dr. von Arthaber says further that there are at least two varieties, 
M. Jaekeli and WM. Moreli, the former the smaller, the latter the 
larger type. It would seem that some Continental paleontologists im 
their desire to discover new species forget to take into consideration 
such trifles as age or sex in relation to size. 
Ten skulls of IL superciliosus in the Kyebury Collection show 
various degrees of length and stoutness, but in all the general pro- 
portions are similar, and the sculpture of the frontal bones is identical, 
though less strongly marked in some than in others. 
Mr. Lydekker, in the Catalogue, part iv, Suppl., p. 282, says with 
regard to MW. superciliosus: ‘‘In the type cranium the prefrontals. 
have only a very short sutural junction with the frontals and a straight 
inner border, whereas in the type of JL. Blainvillei of the Kelloway 
Rock the prefrontals have a long sutural junction with the frontals 
and a convex inner border. The large series of skulls in the 
collection of Mr. A. N. Leeds shows, however, such a great variation 
in these respects that they cannot be regarded as of specific value.” 
The natural deduction, therefore, is that if these characteristics are 
unreliable for definitely determining the difference between JZ. super- 
ciliosus and M. Blarnvillei, still greater care must be taken not to 
create new sub-species of If. superciliosus, which shows such variation. 
The list of measurements (in millimetres) which I give below is 
taken from ten skulls practically perfect, except the last one, all in the 
Eyebury Collection, which I think will bear out my point that while 
they show for the most part similar proportions, they present here and 
there curious variations. The explanation of these variations is not 
1 Zeitschr. Deutsch. Geol. Gesellsch., Bd. lvi (1904), Monatsber., p. 97. 
2 « Beitrige zur Kenntnis der Organisation und der Anpassungserscheinungen des 
Genus Metriorhynchus’’: Beitrige zur Paliont. und Geol. Osterreich-Ungarns und 
des Orients, Bd. xix (1906), p. 293. 
3 Thid., p. 288. 
