BATRACIIIA. 285 



pedicles of their lower jaw, which is extremely dilatable; all their body-scales are equal, of small size, and disposed 

 hexagonally. To these subgenera I have added that of 

 Cheriydrus, — 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 

 Datrachians, although we are not aware that it undergoes any metamorphosis. It is that of 



The Coccilians (Ccecilia, Lin.), — 

 So named on account of their excessively minute eyes, which are nearly hidden by the skin, and are 

 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 

 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 

 extremity of the body, the ribs much too short to encircle the trunk, the articulations of the vertebrae 

 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 Amphisbaenes only, among the other 

 Ophidians ; their maxillary bones cover the orbits, which are pierced by only a very small foramen, and 

 the temporal bones extend over the fossa, so that the skull presents a continuous bony buckler above ; 

 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'lnteans, 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 lamina;. In their intestines have been found vegetable iuatter, 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. a mi nl a tn of Urazil, 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 ft lumbricoides, Daudin ; it is of a blackish colour, two feet long, and no thicker than a 

 goose-quill. 



THE FOURTH ORDER OF REPTILES — 



THE BATRACHIANS,— 



Have but o~e 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 Pishes, 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 L'Uls 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 duccth . 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 ait i r\ . each giving oil' a small branch to the lung of its particular 



side, so thai the circulation of a Fiah becomes thus converted into tint oi a Reptile. 





