DISTRIBUTION OF OPHIDIANS. 201 



^vllere that of innocuous snakes seems to diminisli. Africa 

 and New Holland furnish examples of this : in the former 

 continent the species of known innocuous serpents are in 

 the ratio of two or three to one, whilst it is almost the re- 

 verse in New Holland, where, of the ten known species of 

 snakes, there are seven venomous. As to the number 

 of individuals, it is much more limited in the venomous 

 serpents, these last, with the exception of the Sea-Snakes, 

 almost always living solitary, and not multiplying ever 

 to the point of becoming abundant, except by a concurrence 

 of very favourable circumstances ; as has happened in the 

 sugar colonies of France, in regard to the Trigonocephalus 

 lanceolatus, or in Dalmatia, in regard to the Vipera am- 

 modytes. Venomous serpents, then, belong generally to 

 the rare class, and they are perhaps much more rare than 

 is usually conceived ; either because the number of indi- 

 viduals is often very circumscribed, or because, thanks to 

 their habits, they more readily escape the observation 

 of mankind.* Excepting the anomalous species which 

 compose the family of Tortrix, there exists not one 

 s^Decies of serpent, v,hich is at the same time spread 

 over all parts of the globe inhabited by reptiles ; and 

 this curious fact v/ill serve to demonstrate how intimate 

 is the relation subsisting between the organization of 

 beings and the nature of the places they inhabit. The 

 True Colubri, for example, which are destined to inhabit 

 countries woody or marshy, but covered with an abundant 

 vegetation, have not yet been found in New Holland, and 

 are so rare in Southern Africa, that only a single species 

 is known, which departs, moreover, in several points in its 

 structure, from other Colubri, inasmuch as it approaches 

 to those serpents that prefer to inhabit desert or sandy 

 countries. We may apply almost the same observations 

 to the genus Coronella — serpents which inhabit marshy 



* The numerous packages which are continually addressed to the 

 museums of different countries, might furnish a ?cale of comparison, 

 to ascei'tain the relative number of individuals of the two great tribes 

 of serpents : the researches which I have made on this head, have proved 

 to me that, at an average, the number of individual venomous serpents 

 is to that of individual innocuous sei'pents as one to twenty. 



