858 The American Naturalist. [September, 
and some others do not, however, agree that the suspensorium in the 
snakes is the paroccipital, but call it squamosal and other names. I 
was led to identify it with the former element of the Testudinata, etc., 
by a consideration of its structure in the Pythonomorpha,’ where it is 
much more largely developed than in the Lacertilia, and where it sup- 
ports the quadrate bone as in the Ophidia. The accompanying fig- 
ures make this more clear, The paroccipital bone is received deeply 
between the exoccipital and the petrosal in the Pythonomorpha in the 
same manner as in the Tortricine snakes: a structure which does not 
occur in the Lacertilia. This structure is somewhat masked in some 
genera of Pythonomorpha by the extension of the exoccipital over the 
paroccipital as a thin lamina on the posterior side ; in that case its true 
relation to the petrosal can be seen on the anterior side, In the Lacer- 
tilia the quadrate merely touches the paroccipital bone, whose distal end 
has a convex surface (Figs. 1, 1a), but it articulates with the exoccipital 
bone. This it never does in the Ophidia and Pythonomorpha. This isa 
fundamental difference between Lacertilia and Pythonomorpha to be 
added to those which I have already given. 
For this reason, and in view of the various important differences from 
the Varani, it is necessary to believe that the Pythonomorpha form a 
line distinct from the Lacertilia, and that their resemblances to the 
Varani are the result of a parallel evolution rather than an indication 
of near affinity. 
The failure of Cuvier, Owen, Dollo, Baur and Marsh to perceive 
this fact is due to their want of information as to what the differences 
between the Ophidia and Lacertilia really are. 
From this point of view the Ophidia and Pythonomorpha must be 
traced to some type in which the paroccipital bone is less remote from 
the brain case than is seen in the Lacertilia, where it has become a 
mere rudiment. Such a phylogeny could be expressed as follows. An 
investigation of ths Dolichosauria of the Cretaceous might yield inter- 
esting results. 
Lacertilia Pythonomorpha Ophidia 
Sp 
tin oe 
Common ancestor with ambulatory 
limbs and sessile paroccipital. 
3L. c., and the Cretaceous Vertebrata of the West, U. S. Geol. Surv. Terrs, 
Vol. II, 1875. 
