BATIIACHIA. 
285 
pedicles of their lower jaw, which is extremely dilatable ; all their body-scales are equal, of small size, and disposed 
hexag-onally. To these subgenera I have added that of 
Chersydrus, — the head and body of which are equally covered with small scales. 
THE THIRD FAMILY OF OPHIDIANS,— 
The Naked Serpents, — 
Comprises but one very singular genus, which several naturalists have deemed to belong rather to the 
Batrachians, although we are not aware that it undergoes any metamorphosis. It is that of 
2 The CoeciLiANS {Cmcilia, Lin.), — 
1 So named on account of their excessively minute eyes, which are nearly hidden by the skin, and arc 
:j sometimes absent altogether. The skin is smooth, viscous, and annularly wrinkled, appearing naked, 
although, upon dissection, some perfect though minute scales are discernible, which are regularly 
ji disposed in several transverse ranges between the wrinkles of the skin, and which we have detected, 
] with certainty, in more than two species. The head is flattened, the anus round and nearly at the 
■I extremity of the body, the ribs much too short to encircle the trunk, the articulations of the vertebrae 
I'j together are by conically hollow facets filled up with gelatinous cartilage, the same as in the Fishes 
!! and some of the lower Batrachians, and, in a slight degree, in the Amphisbsenes only, among the other 
j Ophidians ; their maxillary bones cover the orbits, which are pierced by only a very small foramen, and 
iS the temporal bones extend over the fossa, so that the skull presents a continuous bony buckler above ; 
j! their hyoid bone, composed of three pairs of arcs, induces the supposition that it originally supported 
|! gills. The maxillary and palate teeth are arranged in two concentric lines, the same as in the 
I Proteans, but are often sharp and curved backward, as in the Snakes properly so called ; the nostrils 
^ open behind the palate, and the lower jaw has no moveable pedicle, the tympanic bone being encased, 
together with the other bones, in the buckler formed by the skull. 
The auricle of the heart of these animals is not divided so deeply as to be considered double, but 
their second lung is as small as in the other Serpents ; the liver is divided into a great number of 
transverse laminae. In their intestines have been found vegetable matter, together with soil and sand. 
Their ear has merely a small plate upon the oral orifice, the same as in the Salamanders. 
Some of them have an obtuse muzzle, lax skin, very deep wrinkles, and two small cilia? near the nostrils ; as 
C. annulata of Brazil, which is found in marshy places several feet under ground, C. glutinosa of Ceylon, &c. ; 
while others have the folds of the skin nearly obsolete, a very long slender body, and projecting muzzle. One of 
these is totally blind, the C. lumbricoides, Daudin ; it is of a blackish colour, two feet long, and no thicker than a 
I goose-quill. 
THE FOURTH ORDER OF REPTILES,— 
THE BATRACHIANS,— 
Have but one auricle and one ventricle to the heart, [an assertion disproved by Professor Owen]. 
Their two lungs are always equal, and when young they conjoin to these, gills, which give them 
a relationship with the class of Fishes, and which are borne on the sides of the neck, upon the 
cartilaginous arches which support the hyoid bone. The greater number lose these gills, 
together with the supporting apparatus of them, upon attaining the perfect state : three genera 
only, the Syrens, Protei, and Menobranchi, retaining them at all ages. 
During the period of the retention of the gills, the aorta, on proceeding from the heart, 
divides into a number of branches upon each side, corresponding to that of the gills ; the 
blood from the gills returning through veins which unite together towards the back, into a 
single arterial trunk, as in Fishes : this trunk, or the veins which form it more directly, supplies 
the greater number of arteries which nourish the body, and even the vessels which conduct the 
blood for respiration into the lungs. But in the species which shed their gills, the vascular 
ramifications that communicate with them become obliterated, excepting two, which unite 
together to form a dorsal artery, each giving off a small branch to the lung of its particular 
side, so that the circulation of a Fish becomes thus converted into that of a Reptile. 
