PRIME VAL SALAMANDERS. 
3 i 3 
the adult. Varying from the size of a small newt to that of a crocodile, the 
primeval salamanders are of especial interest to the evolutionist, as it is pretty 
certain that not only are they the descendants of primeval fishes, but that 
they are the ancestors both of the modern Amphibians and the extinct Anomodont 
Reptiles. And it is probable that Mammals have originated, either directly from 
them or from a lost group intermediate between them and the Anomodont 
Reptiles. They appear to have been spread over the whole globe, and they have 
been divided into several subordinal groups. Among 
these the highest are the true Labyrinthodonts, 
typically represented by the gigantic Mastodonsaurus 
and the somewhat smaller Metoposaurus of the Trias. 
These were crocodile-like animals, generally with 
disc-like vertebrae in the adult, the teeth more or 
less plicated, and the surface of the skull marked 
with sculpture and mucous canals. In the Permian 
Archegosaurus, the vertebrae were, however, of the 
complex primitive type. The Gilled Labyrinthodonts, 
as represented by Protriton and Pelosaurus, are a 
group of much smaller forms, characterised by their 
barrel-shaped vertebrae, pierced by a remnant of the 
canal of the primitive notochord; short and straight 
ribs, articulating by a single head; simple teeth, and 
the absence of ossification in the occipital region of 
the skull, as well as in the wrist and ankle-joints; a 
further point of distinction being the development of internal gills in the young. 
The Permian and Carboniferous Snake-like Labyrinthodonts are characterised by 
the snake-like form of the body, and the apparent absence of limbs. The vertebrae 
were elongated and without spines, while the ribs were slender and barbed like 
those of fishes, and the teeth smooth and simple. Probably the external gills 
persisted throughout life. In Britain the group is represented by the small 
Dolichosoma ; but Palceosiren of Bohemia is estimated to have been over 40 feet 
long. If these creatures prove to be the ancestors of the Worm-like Amphibians, 
it would show that the latter are distinct from the newts and salamanders. The 
Microsauria, include small lizard-like forms, such as Ceratoerpetum and Hylonomus 
from the Carboniferous of Europe and Nova Scotia, which appear more highly 
organised than the preceding, and thus connect the Amphibians with the Beaked 
Reptiles. Their vertebrae are long and constricted, with traces of the notochord; 
the ribs are generally long, curved, and two-headed; the teeth have large central 
pulp-cavities, but no plications; the occiput is ossified ; but the wrist and ankle are 
either ossified or cartilaginous; and in some cases the back is covered with bony 
scales. In several forms the bony scales on the under surface are so slender as to 
assume the appearance of abdominal ribs like those of the Beaked Reptiles. 
