310 NATURAL HISTORY 
at the vent, the tail shorter, the teeth much larger and 
more distant, and the colour brown instead of black* 
This animal is probably amphibious, although it has 
not the flat tail of the Pelamides; nor did the examina- 
tion of its exterior enable us to discover any thing in its 
structure, peculiarly adapting it to a residence in the 
water, excepting only the remarkable facility of bending 
in a vertical direction. This motion, which may be ob- 
served in the leech, -and various other aquatic animals, 
is quite as important as a horizontal one to an inhabitant 
of the ocean, and comparatively useless in an animal con- 
fined to the land. 
Internal Structure.— The structure of the spine in this 
animal is very singular, and different from that of any 
serpent which we have seen, or known to be described. 
Its course throughout the greater part of the body is 
regularly undulating or flexuous, consisting of successive 
curves upward and downward. The structure of the 
different vertebrae varies to accommodate itself to this 
configuration, so that the spine cannot be extended into 
a straight line without dislocation of its parts. In the 
portion of spinal column which we examined, each curve 
consisted of about nine vertebras. Each vertebrae was 
articulated by a round head on its posterior extremity 
to a socket in the anterior extremity of the next. It 
had five principal processes, one a spinous process; two 
anterior, and two posterior transverse processes. There 
were also smaller processes articulated with the ribs, and 
a sharp longitudinal prominence underneath. The spi- 
nous processes varied remarkably in shape and size, ac- 
cording to the part of the spine in which they were situ- 
ated. Those occupying the top of the curve were very 
broad, and those of the bottom of the curve very narrow, 
the latter being not more than half the breadth of the 
former. The top of the spinous processes in the ascend- 
ing or anterior half of each elevation of the back-bone 
projected considerably backward. In the descending 
half, on the contrary, they projected forward, so as to 
appear as if this part of the spine were inverted. The 
space between the spinous process was very great, 
