164 ox THE niYSIOGNOMY OF SERPENTS. 



Fresh-Water Serpents. These serpents approach by 

 their organization more or less to the Colubri, and live in 

 the water, or at least prefer the neighbonrhood of rivers 

 or of lakes to other ])laces. I do not mean to say that 

 all the Ophidians which have siniihn* habitudes should be 

 united to this family, otherwise it would oblige us to 

 range in it the Colubri, and most of the Boas, which pre- 

 sent a very different organization. I have rather as- 

 sembled under this appellation the serpents of which I am 

 to treat ; because, with certain analogies in their organiza- 

 tion and physiognomy, they compose a natural group, but 

 by no means separated by precise characters from other 

 subdivisions. This family conii)rehends two genera, the 

 first of which, with some slight exceptions, presents 

 nothing interesting in the structure, while the species of 

 the second are all characterized by peculiarities as marked 

 as curious. The first is the 



TROPIDONOTUS, 



which constitutes an assemblage of serpents, very ana- 

 logous to the genus Coluber, but the forms of which are 

 more heavy ; which have the belly very broad and con- 

 vex, the head broad and conical, but narrow at the sum- 

 mit, with a short muzzle. The eye is not large, and 

 the nostrils are but little open. These snakes have ordi- 

 narily 3 plates behind the eye ; 19 rows of scales, of a 

 lozenge form, and carinated, the angle of the mouth turn- 

 ing upwards. The colour of the Tropidonotus is often 

 sombre, but varied with spots of vivid hues ; they do not 

 arrive at a great size, and most of them do not surpass 3 

 or 4 feet in length. They inhabit the vicinity of fresh- 

 water, or even in the water, and are very good swim- 

 mers. Livmg in society, they are common in the places 

 they frequent ; and the genus is rich in species. They 

 have not yet been observed in New Holland, nor in South 

 America, where they are replaced by the Homalopsis. 

 Southern Africa supports but a single species, remarkable 

 by its anomalous organization. 



1. Tropidonotus Natrix inhabits the whole of Europe 



