ex INTRODUCTION. 
possession of rudiments of limbs not visible externally. A few lizards 
have the ears covered by the skin, and others have no eyelids. There are 
serpents and lizards which have similar forms, motions, and habits. The 
extent of variation may best be seen by comparison of the examples cited 
below. 
Development of the senses varies according to habits. In the serpent- 
tongued lizards we meet with great quickness of sight, hearing, scent and 
touch, accompanied by lack of taste—the tongue simply being a very sen- 
sitive tactile organ. Again, in species living upon vegetation, the touch is 
deficient and the tongue is short and thick, evidently an organ of taste. 
The keen-sighted Chamaeleon has a tongue which is probably an organ 
of taste as well as touch. 
Many of the Saurians are noted for transient variations of color. The 
cause of these changes is found in the presence of pigments of different 
colors at various depths below the surface of the skin. The expansion or 
contraction of one or more of the layers, in consequence of muscular action, 
nervous irritation, or contraction or inflation of the lungs, changes the pro- 
portion of the different pigments visible at a particular instant. If the 
upper layer contains the dark pigment, the contraction of its chromato- 
phores lessens the visible amount of this color and exposes a greater amount 
of that beneath it. These changes are not to be confounded with that occur- 
ring on soils of light color, or in regions where there is great reflection of 
the rays of light; in such localities permanent lightening of the colors is 
apparently due to a bleaching process undergone by the pigments. It seems 
as if the effect of polarized light upon the pigment differed from that of the 
direct unpolarized rays. Commonly each vertebra is concave in front and 
convex behind. To this there is a very marked exception in the case of the 
RuYNCHOCEPHALTA, a suborder founded on a family represented by a single 
genus of New Zealand lizard, Hatteria or Sphenodon. Externally this ani- 
mal resembles the species of the European genus Lacerta so much that one 
can hardly believe it more than generically distinct. Skeletal structure and 
details of anatomy discover differences of sufficient importance to warrant 
the establishment of a different order. Most noticeable of its peculiarities 
are the series of palatine teeth, the structure of the skull, the biconcave 
vertebree, the presence of a cartilaginous rib beneath each transverse fold 
of the skin of the abdomen, and the absence on the male of intromittent 
sexual organs. Of those examined the females were lighter in color, and 
—_ ats 
