OPHIDIA. 57 



greater or less extent, which enables these animals so to dilate 

 their mouths as to swallow bodies larger than themselves. 



Their palatine arches participate in this facility of motion, 

 and are armed with sharp pointed teeth which curve back- 

 wards, the most predominant and constant character of the 

 tribe. Their trachea is very long, their heart very far 

 back, and most of them have but one large lung with a vestige 

 of another. 



Serpents are divided into venomous and non-venomous; 

 and the former are subdivided into such as are venomous with 

 several maxillary teeth, and those which are venomous with 

 insulated fangs. 



In such as are not venomous, the branches of the upper 

 jaw as well as those of the lower one, and the palatine arches, 

 are every where furnished with fixed and solid teeth ; there 

 is then four equal rows of these teeth in the upper part of the 

 mouth, and two below. (1 ) 



Those which have the mastoid processes comprized in the 

 cranium, the orbit incomplete behind, and a thick, short 

 tongue, still retain much similitude to the Atnphisbsenx in 

 the cylindrical form of their head and body, and were for- 

 merly united with Anguis on account of their small scales. 

 They constitute the 



ToRTRix, 0ppel.(2) 



And are otherwise distinguished from the Anguina, even exter- 

 nally, inasmuch as the scales which form the range along the belly 

 and under part oi" the tail are a little larger than the others, and the 

 tail itself is extremely short. They have but one lung. 



(1) The common opinion respecting them is, that those which are destitute of 

 the pierced fangs in front of the jaws are not venomous, but I have some reason to 

 doubt its correctness. They all have a maxillary gland, which is frequently very 

 large, and their back molars exhibit a groove which may serve to convey some fluid. 

 It is very certain that several of the species in which the back molars are very large, 

 are accounted extremely venomous in the countries they inhabit, and that the ex- 

 periments of Lalande and Leschenault have served to confirm that opinion; their 

 repetition is much to be desired. 



(2) They are the Anilius, Oken, the ToaauAXRix, Gray, and the Ilysia, 

 Hemprlch and Fitzinger. 



Vol. II.— H 



