242 B. NATURAL HISTORY. 
two centra a mass of cartilage. In the Batrachia, the ossification 
of this mass produces the ball which adheres to the centrum 
in front or behind, producing the procelian or opisthocclian ver- 
tebra. The vertebre of Gecconide are therefore probably in the 
embryonic form of those of the other Lacertilia. Not so, how- 
ever, with the Triassic genera in question. According to Meyer's 
figures, they are nearly plane, like those of Sphenodon and Dino- 
sauria; and were probably developed round the ‘chorda dorsalis, 
without retention of included ball. , ; 
In Phanerosaurus, the neural arches are united to the body by 
suture, a character unknown in the Lacertilia. In general the ver- 
tebree by which the genus is known might as well belong to a 
Sauropterygian. In Proterosaurus (See Von Meyer’s “ Saurier aus 
dem Kupferschiefer,” Plates), the forms of the inferior pelvic bones 
and the presence of inferior abdominal ribs, are so entirely unlike 
any thing in the Lacertilia, and so much like the same parts in 
Sphenodon, that this genus also, I have no doubt, is a ‘Rhynchoce- 
phalian. Every thing is in favor of the supposition that Rhyncho- 
saurus and Sphenosaurus are Rhynchocephalians, since the parts | 
preserved correspond with those of known types of that order, and 
none of the special peculiarities of Lacertilians, as distinguished 
from the former, have been discovered. 
The only genera remaining are Saurosternum (Huxl.) and Teler- 
peton (Mant.). In the latter genus the palatine bones are said not to 
be separated by fhe pterygoids, and there is no quadratojugal repre-, 
sented by Huxley: if these characters exist, it suggests the Lacer- 
tilia rather than Rhynchocephalia. The latter is the more important 
point; but further examination is necessary to decide on it, as the 
postorbital arch is also omitted in the figure, which is possibly an 
inaccuracy, consequent on the state of the specimen. The form is 
in its derttition equally like the Lacertilian Uromastix and the 
Rhynchocephalian Sphenodon; but the transverse direction of the 
parieto-squamosal arch, and the plane or concave articulations of 
the vertebral centra, are those of the latter, not of the former. 
As to Saurosternum, not enough is known of the only specimen 
to ascertain whether it belongs to the Lacertilia or Rhynchocepha- 
lia. There is no cranium, and the parts preserved or described 
are as characteristic of one order as the other. 
10. Stratigraphic Relation of the Orders of Reptilia. 
This is most readily shown in tabular form, as follows : — 
