What are the characteristics of snakes?

Snakes have long bodies that taper into tails. They do not have limbs, and their movement is a result of
undulating movements of the body. The scales on the underside of the body project outward as the muscles
are contracted and relaxed. These scales exert pressure on the surface and move the animal forward.
The skin of snakes has a horny surface layer that forms a hard, continuous covering of scales. These scales
lie beneath the outer layer of the epidermis so that the body can grow. As the animal grows, this outer layer is
shed, allowing for further growth.
Snakes cannot close their eyes. Instead of eyelids, they have a transparent layer, or brille, that permanently
covers the eye. During the shedding process, this layer over the eye is shed and replaced with a new covering.
Nocturnal species have vertical pupils that open very wide in dim light and close to small slits or pinholes in
bright light. Diurnal species have round pupils.
Snakes have teeth that are fused to the jawbones. Some snakes also have teeth fused to the palate bones,
and some have teeth connected to poison glands. All snakes have long, slender, forked tongues.