DISTRIBUTION OF OPHIDIANS. 
201 
where that of innocuous snakes seems to diminish. 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 Trigonocephaliis 
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 
species of serpent, which is at the same time spread 
over all parts of the globe inhabited by reptiles ; and 
this curious fact will 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 scale of comparison, 
to ascertain 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 serpents as one to twenty. 
