O74 ZOOLOGY. 
Fam. 2. Chaleidide. This family, with a striking resemblance in external 
form to some members of the last, is readily distinguishable, as already re- 
marked, by the different disposition of the scales, or the markings of the skin, 
and by the lateral furrow found in many species. We find some species 
provided with four legs, others with but two; while another series, again, is 
entirely serpentiform in appearance, owing to the absence of these members 
exterior to the skin. There is rarely any constriction posterior to the head, 
answering to a neck, the body and head being usually continuous. The scales, 
instead of being imbricated or arranged like those of most fishes, are disposed 
in whorls or rings inclosing the body. In other cases, where the scales 
(photides) are absent, furrows in the indurated skin present similar markings. 
The dorsal and ventral scales, like those of the Scincide, and unlike what we 
shall find to be the case in the Lacertide, are arranged much in the same 
manner, and are of no striking difference in size. The teeth are not im- 
planted in the jaws, but applied along the inner margin, thus exhibiting 
the true pleurodont character. The tongue is free, slightly extensible, broad, 
and emarginate at the tip, clothed with filiform or scaly papillz, and not 
plying ina sheath. The ears are apparent externally in some species, while 
in others there are no such indications of them. The eyes are generally 
small, and slightly developed. Some species have movable eyelids ; in others 
these organs are not movable ; while in a few the skin covers the entire ball 
of the eye. 
This family is confined mainly to Africa and America, although a few spe- 
cies are found in other regions of the globe. Mexico, California, and the 
southern United States contain quite a number of them. The entire number 
of species described amounts to about 50, arranged in 16 genera. 
We distinguish the Chalcidide into two sub-families, according as the 
skin is covered with scales or is free from these appendages. The first sub- 
family, that of the Ptychopleures, possesses true scales arranged in the 
manner already described. All the species, with a few exceptions, have a 
longitudinal furrow, more or less deep, on each side; and, without any ex- 
ception, are in the possession of eyelids. Some species possess an external 
auditory cavity, others are without one. The first genus to be mentioned is 
Ophiosaurus (pl. T4, fig. 63), an inhabitant of North America, and known as 
the “glass snake.” This animal, although usually considered as a serpent, 
may readily be distinguished by the compact skull and non-dilatable mouth, 
the fleshy tongue, the external auditory cavity, and the peculiar distribution 
of the scales. The name is derived from the fact that a slight blow is suf- 
ficient to produce a fracture of the very brittle body, the muscles of which, 
instead of the longitudinal arrangement of the serpents, have the arrange- 
ment in hollow cones so conspicuous in the equally brittle tails of lizards. 
It is a common, although entirely erroneous opinion, that the pieces of a broken 
glass snake will reunite after a time. Two species are known in the United 
States, one, O. ventralis, restricted to the Southern or South Eastern States, 
the other, O. lineatus, occurring in the South West, and as far north as 
Michigan. 
In the genus Pseudopus, a native of Eastern Europe and of Africa, we 
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