816 General Notes, [August, ; 
In the first place, Lemoine shows that the genus is streptostyl- 
icate, and that the quadrate bone has much the character of that 
of the Pythonomorpha, It can, therefore, only be properly com- 
pared with that order, the Lacertilia and the Ophidia. The sin- 
gle rib-heads and the separate odontoid bone are entirely con- 
firmatory of this affinity. There is therefore no longer any pro- 
priety in comparing it with the Rhynchocephalia or the Croco- 
dilia. Is it a Lacertilian or a Pythonomorph, or to what division 
of the streptostylicates is it to be referred ? 
r. Lemoine has discovered what he regards as a distinct cran- 
ial segment (“vertebra”) interposed between the occipital and 
parietal segments in this genus. This is very remarkable, and 
constitutes a strong mark of distinction between the Choristodera 
‘and Lacertilia. It will depend on future investigations to show 
whether such difference exists between this order and the Pytho- 
nomorpha and Ophidia. In this question everything depends 
on the interpretation of the pieces. The new segment consists, 
according to Lemoine, of an “anterior basioccipital” as axis, 
which is surmounted by the opisthotic, and this by the epiotic on 
each side. It is closed above by the supraoccipital (Etude, p. 14). 
The segment in front of this Lemoine identifies with the sphe- 
noidal. Its axis, then, becomes the sphenoid bone, and its = 
eral pieces the proôtics. According to Lemoine’s figure aes 
latter elements meet on the middle line above, and the pare" 
lies above them. A notch on the lower part of the front p a 
of the so-called prodtic is identified with the foramen 0 
trigeminal nerve. ; : 
ithout access to similar specimens it is impossible to eed 
whether any of the axial pieces of this skull is a parasphener 
not. In any case we shall learn something by comparison © 
the snake and pythonomorph skull. Each of these, as abid 
known, presents a decurvature in front of the prootic igen t fifth 
reaches to the sphenoid or presphenoid. The foramen 0! zj by 
nerve is posterior to this, in the position of the one amg Fd 
Lemoine to the eighth nerve. If now we identify pee [g 
Otic with the lateral or “alisphenoid ” plate of the ae cranial 
ment of the above orders, we have the normal number 0 roôtic, 
segments remaining. The “opisthotic ” (fig. 4) beot is the 
and the “ anterior basioccipital ” becomes sphenoid. tylicate rep: 
ner of the anterior elements described by Lemo ‘to that of the 
To the resemblance which this structure bears ‘of the 
Ophidia must be added the absence of true roots 0! 
