MEYER, REPTILES IN THE COAL FORMATION. 53 
ceal that he likewise is convinced that it is very difficult to find a 
limit between the parietal and the posterior frontal bone. Behind 
this series of cranial bones follows a second, which the author, pro- 
ceeding from the former, describes as mastoid, tympanal and squamous 
bones (Zitzenbein, Paukenbein u. Schuppenbein); in the Laby- 
rinthodon the reviewer found the malar bone also prolonged into 
this posterior region, and the position of the tympanal and mastoid 
bones, the latter more correctly designated temporal bone (Schlafen- 
bein), is the same. The superior occipital bone extends farther out, 
on the upper side, than in the triassic Labyrinthodonts. When the 
author says that m Capitosaurus the frontal bone (Hauptstirnbein) 
does not touch the inner margin of the orbits, he seems to have 
confused this genus with Metopias, in which the frontal bone does 
not contribute to form the orbit, whereas in Capitosaurus and Mas- 
todonsaurus this margin is formed in the same manner as in Arche- 
gosaurus. ‘The circular parietal foramen in 4. Decheni lay nearly in 
the middle of the parietal bone, and was relatively larger than in the 
known Labyrinthodonts ; and in the two other species of Archego- 
saurus it was smaller, and, in consequence of its appearance in the 
anterior half-length of the parietal bone, came nearer to the orbit. 
The temporal fossa also exhibited some diversities ; in Archegosaurus 
it begins anteriorly with a narrow fissure which suddenly widens pos- 
teriorly ; whilst im Mastodonsaurus, in which it appears most di- 
stinetly, it is much shorter and expands in front in a circular manner. 
The occipital foramen, as well as the articular process of the occiput, 
are not yet made out, but from the other parts of the structure of 
the Archegosaurus, the reviewer has no doubt that this process was 
bicondylous, as in the Labyrinthodonts. The jaws, to beyond the 
orbit of the eye, were furnished with small, fine, conical teeth, 
beyond which some thicker ones have projected, but even the latter 
were not so strong as in the Labyrinthodonts. It is still uncertain 
whether the jaws, as in the latter animals, were furnished with several 
rows of teeth. Instead of the teeth only their impression in the 
stone remains, from which it is seen that they were striated longi- 
tudinally. The reviewer believes that these teeth were fixed in deep 
alveoli, which was not the case with those of the Labyrinthodon. 
The distinction between A. medius and A. minor—the skulls of 
which more resemble each other than they do that of 4. Decheni,— 
consists rather in the constant difference in size, than in other cha- 
racters. In these species the thickness of the nasal bones more 
approximates to that of Capitosaurus, and the frontal bone is, as in 
Labyrinthodon, double [7. e. divided by a frontal suture]. In the 
orbits of the eyes the author found long, quadrangular plates, still 
partially arranged in a semicircle ; whence it follows that the eye of 
these animals was furnished with an osseous ring, which the reviewer 
has not found in the Labyrinthodonts of the Trias. The under jaw 
has small teeth like the upper jaw, and these can also be followed to 
beyond the orbit. On the anterior end of the intermaxillary bone, 
small, fine teeth appear, and behind three stronger teeth, which the 
author considers canine teeth. This view the reviewer can confirm 
F2 
