AND CLASSIFICATION OF TUE FOSSIL REPTILIA. 
28 .‘i 
referable to Clepsych'ops natalis {Qoye)‘^, is classed as Pelycosaurian. A similar 
tarsus was subsequently referred with doubt to the genus Theropleuro It is difficult 
to judge of its importance. Its characters appear to be more Mammalian than those 
of the Crocodilian tarsus, for the Ijones of the distal row are completely ossified. The 
tarsus is absolutely unknown in any Anomodont from Africa, Europe, or Asia ; and, 
therefore, there is no means of comparison with this American fossil. 
The Pelycosauria are said to have two or three sacral vertebrae, a notochordal 
column, and inter-centra usually present. With the evidence that Dinosaurs may 
have as few as two sacral vertebrae, as well as a larger number than has been found 
Fig. 5. 
in any Anomodont, this ground of ordinal distinction fails. Similarly, the mode of 
ossification of the inter-vertebral substance presents many types among Anomodonts, 
one of which already figured by Sir P. Owen might be regarded as notochordal. 
What the value of the inter-centra may be I am unable to say, as they have not 
been figured; but, inter-centra, as I understand them, are not unknown among 
Anomodonts. 
The remarkable vertebral column with vertically eloirgated neural spines referred to 
Dimetrodon is* apparently unlike any known Anomodont, but the elongation of the 
neural spines in certain Wealden Peptiles, like (?) Ilylceosaurus, is not considered to 
militate against their position in the group to which they belong. And it may be 
doubted if the more extraordinary neural spine of Naosauras {loc. cit., Plate III.), 
with its transverse branches, has any greater classificational value, since the transverse 
branches are the only character by which the author separates Naosaiirus from 
Dimetrodon. In IheropAeura, which is also described as having elevated neural 
spines, abdominal dermal rods are found. These appear to be of the same nature as 
* ‘ Araer. Phil. Soc. Proc.,’ August, 1884. 
f ‘ Amer. Pliil. Soc. Trans.,’ vol. 16, Plate III. 
2 o 2 
