Review of Recent Geological Literature. 03 
The author figures the classic Mosasaurus of Maastricht found in 1785 
and for nearly a century the only specimen of the genus. This speci- 
men which had some singular experiences during the war in the "'Low 
Countries ** is inferior in one important respect toothers which have 
been since found in the Cretaceous of North America, inasmuch as the 
displaced pterygoid bone conceals the joint in the ramus of the jaw that 
is a peculiar feature in the family of the Mosasaurklcc, and, according 
to Baur. in at least two others, the Varanidce and the Helodermatidce. 
So complete is the concealment of this feature that its very existence 
was unknown until the American specimens were found. 
Of the dinosaurians the author writes: "They comprise the largest 
land reptiles and while some of them approximate closely to the type of 
structure obtaining in birds others come so near to the more generalized 
erocodilians that it is almost impossible to separate them from the 
latter." Here belong the long known Iguanodon, the subject of the 
labors of the late Dr. Mantell: the Hadrosaurus, first described from tho 
Cretaceous of North America but since found in Europe, the only skel- 
eton of which is in the museum at Princeton, N. J., the work of the late 
Waterhouse Hawkins; the immense Megnlosaurus and horned Ccrato- 
*<Lurus, Ceratops, with beak-like skull and one or more pairs of horn-like 
processes resembling those of cattle; Brontottierlum of North America 
and Europe, estimated at 50 feet in length and 20 tons in weight, and 
lastly the but partially known Atlo/ntosaurus with a femur more than 
six feet long and probably the largest land animal yet known. 
Among the Reptilia also occur the strange flying Pterodact vies, per- 
haps the earliest animals, insects excepted, which possessed the power 
of rising into the air. Geology has not revealed the remains of any 
true bird of date coeval with them. They were not, however, birds at 
nil. but flew as bats, by the aid of flaps of the skin carried on the enor- 
mously developed phalanges of the limbs. "The greater number of 
the bones were hollow and frequently provided with pneumatic fora- 
mina as those of birds. The brain was bird-like and the skin was 
-probably naked. The order ranges from the Lias to the Upper Chalk. 
In spite of the many remarkable resemblances in structure to that of 
the carinate birds it is clear that thePterodactyles are altogether off the 
line of direct avian descent." In some of these strange animals the 
teeth are totally absent (Pteranodon). In others both jaws are toothed 
to the extremities. Some were small — only a few inches in length' 
others had a spread of wings equalling twenty-five feet. All have lon<>- 
been extinct. 
Leaving the reptiles for the birds, we pass over what was once con- 
sidered, perhaps, the greatest gap in structure in the whole animal king- 
dom. The transition from the cold-blooded, creeping reptile to the hot- 
blooded bird is certainly as great as can well be imagined. Hut this gap 
has been so completely filled with tho many forms that palaeontology 
has discovered that it has absolutely disappeared and the difficulty now 
is to distinguish the bird from the reptile. The only evident externa] 
