510 SLD ILE SO RMS RCL EINES: 
pletely covered with thick and heavy membrane bones that showed 
a deep and intricate sculpture; the whole head was flattened and 
either very broad in proportion to its length or long and croco- 
dilian in aspect; the base of the skull was in large part carti- 
laginous; the limbs were short but very strong, and there were 
five digits on each foot: the tail was of moderate length; the 
pelvic and pectoral girdles were strong and broad; the pelvis 
was peculiarly like that of the modern frog in many of the 
forms; the vertebrz were made of several distinct pieces as 
already described. The known forms of the group are almost 
entirely from the Permian rocks of Europe, the East Indies, and 
North America. 
Archegosaurus from the Rothliegende of Germany was rather 
crocodilian in aspect; the head was long and slender and 
joined to a rather elongate body. In youth the animal was fur- 
nished with external gills as in the modern salamanders, which 
were probably shed when the animal reached maturity; the 
dentine of the teeth was arranged in a radial manner the first 
step towards the intricate folding of the enamel in the more 
advanced forms; the clavicles and the interclavicle were broad 
and strong covering to some extent the lower surface of the 
thorax. 
Chelydosaurus from the Rothliegende of Bohemia was shorter 
than Archegosaurus with a broad head and large orbits; the 
dermal bones covering the head were sculptured in a peculiar 
radial fashion. Nearly every portion of the skeleton is known, 
and the preserved bones show that the animal was rather in 
advance of the majority of the forms of the time as they are 
almost entirely free from cartilage. 
Discosaurus 1s a closely related form from the same horizon 
in the neighborhood of Dresden. 
Actinodon and Euchirosaurus are from the lower Permian 
(Rothliegende) of France. The first was much like Archego- 
saurus, but the head was shorter and more triangular in outline ; 
the length of the skull was about 18°". The second genus is 
less well known than the first, but is remarkable for the strength 
