XXil INTRODUCTION. 
then gave it a severe bite in the lip, just as this species of 
spider usually does with any large insect which it has 
taken. The lizard was greatly distressed, and I removed 
the spider, and rubbed off the web, -the confinement of 
which appeared to give it great annoyance; but in a few 
days it died, though previously in as perfect health as its 
companion, which lived for a long time afterwards. 
It has been already observed that the passage from the 
Lizard tribe to the Serpents is by a succession of very 
gradual modifications of developement. In the lower forms 
of the Saurian group, the body becomes gradually elongated 
and serpentiform: its ribs increase in number, the anterior 
and posterior limbs are removed farther and farther from 
each other, and diminish in size and power, exhibiting in 
some forms the anterior, and in others the posterior only, 
external to the integument, until at length they cease to 
appear, being merely rudimentary, and wholly covered by 
the skin. Of this transition state we have an example in 
the common Slow-worm, Anguis fragilis, which, though 
completely Serpentiform in its external appearance, yet 
possesses the minute rudiments of limbs entirely concealed 
under the integuments. Notwithstanding this general form 
of the Serpent, they have not the expansible jaws of the 
true Serpents: nor is the character of the ears the same, 
the tympanic membrane not being superficial, nor the 
auditory passage covered by integument ; the eyes, also, 
like those of the Lizards, are furnished with moveable eye- 
lids, which are wholly wanting in the true Serpents. 
Upon these characters, and several others of minor 
importance, Mr. Gray founded his intermediate order of 
Saurophidians, to comprehend all the transition forms ; 
but it may, perhaps, be objected that the group is not suf- 
ficiently defined to sanction such a distinction. On the 
