24 
ON THE PHYSIOONOMY OF SERPENTS. 
themselves to the extraordinary enlargement of the internal 
parts. 
It results from what we have stated on the nature of 
serpents, that we might exclude from this order the Am- 
phibasna and the Typhlops, although these last are con- 
nected in many respects with the Ophidians, and form 
the transition to these reptiles. It is this approximation 
which renders it difficult, if not impossible, to establish 
distinctive characters for the two neighbouring orders of 
Saurians and Ophidians. Let us illustrate this by some 
examples. The gular fissure, proper to all Ophidians, 
except the Acrochordus, is equally seen in several Saurians, 
such as lizards, &c. Some species of Ophidians shew 
vestiges of posterior extremities, analogous to those we 
find in the Apodal saurians, although their structure 
leads to the belief, that, though the animals last mentioned 
represent the pelvis, while those of the Ophidians corre- 
spond to the posterior extremities. The structure of the 
tongue in the Varanus {Monitor^ Cuv.) and Teius {Saure- 
garde, Cuv.), is scarcely distinguishable from those of 
Ophidians. The want of eyelids does not afford any 
distinctive character ; for these organs occur in every de- 
gree of development in the different species of Saurians. 
Some species, as the Ablepharus and Gymnophthalmus, 
are totally without them ; the minute eyes of the Amphis- 
baena, the Typhlops, and the Acontias coecus, are covered 
by the general integument, in such a manner that these 
animals have so low a degree of vision as to be almost 
blind ; the Acontias Meleagris, on the other hand, has its 
eyes provided with a lower lid ; the Pygopus presents a 
rudiment of a circular eyelid round the whole circumfer 
ence of the eye, without the power of closing that organ ; 
in several of the Geckos, the eyelids appear as prolonga- 
tions of the skin, too little developed to serve as a protec- 
tion to the eyes. One of the most characteristic parts of 
the cranium of Saurians, is the columella, a small pair of 
linear bones which unite the parietals to the pteregoids. 
This bone is wanting, however, in the Typhlops, the Am- 
phisbaena, and even in the Acontias. The development of 
the external ear is found in every shade from the Saurians 
