224 Zoological Society : — 



true cosmopolitan genus. Tropidonotus is one of those which have the 

 widest range, a genus containing about thirty well-known species, 

 each of which bears natural characters so conspicuous, that its posi- 

 tion in the system is not to be mistaken : they are not to be found 

 in the ^Ethiopian region only; they are truly called freshwater 

 Snakes, following the course of the rivers and the borders of lakes. 

 Some of the species {T. natrix, hydrus, quincunciatus, ordinatus, 

 fasciatus) have a very wide range within the borders of its pecuHar 

 region. A few of the Asiatic species exhibit slight modifications of 

 the general appearance of the genus (T. cerasuyaster and vihakari). 

 The second genus, which may be almost called a cosmopolitan, is Co- 

 ronella, being spread over the whole globe except the Indian region, 

 where it is replaced by such modifications of the characters as to 

 justify the separation of them into new genera — Simotes and Ablabes, 

 sp. The latter, closely allied to Coronella, accompanies this genus, 

 extending over all the regions, except over the Australian one. Thus, 

 if I speak hereafter of cosmopolitan genera of Snakes, they are to 

 be understood with the restrictions mentioned. The families of 

 Snakes in the different systems are at present founded upon such 

 general characters, that in most of them genera of some or of all the 

 geographical regions are comprised ; perhaps at some later period 

 they will be limited to more contracted boundaries of less general 

 characters, thus approaching more to the borders of the geographical 

 regions. But for the ])resent we cannot derive from them our de- 

 ductions as to the primary creation of the natural regions of the 

 earth's surface, as the ornithologist does ; and we are obliged to con- 

 fine our views to the genera : we have not even such families of 

 Snakes as are peculiar to one of the two great geographical divi- 

 sions, either to the old world or to the new, except those in which 

 the characters of the family are identical with those of the single 

 genus. This discrepancy between Ornithology and Herpetology may 

 be caused by a different systematic treatment of the characters, and 

 may be more reconciled in course of time ; but there will always re- 

 main forms common to the new and old world. Therefore it is not 

 possible to give a list of Familice Neogeance and FaynilicB PaleBO- 

 geancB (cf. Sclater, I. c. p. 133). 



But I may here give an account of such genera as, I think, will 

 still long remain examples of forms common to the new and old 

 world (cosmopolitan genera excepted) : they are llhahdosoma. Co- 

 luber, Spilotes, Coryphodon, Cyclophis, Philodryas, Bipsas. I could 

 add as many other genera ; but I think such genera as Rhinostoma, 

 Bryophis, &c. will be subdivided hereafter into two. Further, with 

 regard to the aforesaid genera, the same observation as in Ornitho- 

 logy cannot be made, viz. that these are invariably genera belonging 

 to temperate regions, disappearing entirely before we reach Tropical 

 and Southern America. A part of the members of these genera are 

 peculiar to the Neotropical (Tropical America) Ophidio-fauna ; a part 

 reach the Tropics in the old world, and a third part belong to the 

 temperate portions of both hemispheres. 



Taking the amount of similarity or dissimilarity of ornithic life as 



