176 Scientific Intelligence — Geology and Mineralogy. 



occupy a definite area in time. So far, researches seem to indicate 

 that such areas in time are unique for each genus ; leading to the 

 inference by analogy, that the apparent double areas occupied by 

 certain genera in space, are also parts of unique areas. The genus 

 Mitra was cited in illustration, it having several anomalous outlines 

 which the recent researches of the geological survey have shewn 

 to have been parts of an originally continuous area m the epoch preced- 

 ing the present. 



Areas of genera in space being admitted, it remains to see whether 

 such areas had centres, — applying the terms in two senses, viz., 

 points of maximum and points of origin. Tables, shewing the man- 

 ner in which the species of animals and plants are grouped numeri- 

 cally within definite areas in geographical space, were shewn as in- 

 dicating that in every such area there is a point of maximum, and 

 that the number of species diminished around that point. In like 

 manner, in time, the researches of Professor Agassiz among fossil 

 marine vertebrata, and of the lecturer among the invertebrata, were 

 cited to shew that natural groups or genera, were represented by few 

 species at fii'st, increased more or less rapidly to a maximum, and 

 then diminished before disappearing. Professor E. Forbes's re- 

 searches on the fossils of Southern India go to shew, that in all pro- 

 bability the point of origin of a genus is coincident with the point of 

 maximum, and possibly with that of its final disappearance. All 

 these phenomena presented by the distribution of genera, and indi- 

 cating the localization of the type idea, or genus in time and space, 

 are remarkably analogous with those presented by the distribution of 

 the individuals of a species, although there is no true affinity between 

 the two cases. Much yet remains to be done before the numerous 

 problems connected with this subject can be solved. They present a 

 wide and interesting field of research, offering a rich harvest to its 

 explorers, but not to be worked out without the combined aid of 

 zoological, botanical, and geological science. — [Atheneeum, No. 1062, 

 p. 247, March 4, 1848.)* 



2. M. D'Archiac's results of observations made by him on the 

 Quaternary or Diluvian Formation. 



The Quaternary or Diluvian Formation, as we understand it, com- 

 prehends all the phenomena, both organic and inorganic, which have 

 left traces behind them, between the end of the subapennine period, 

 produced by the elevation of the principal chain of the Alps, and the 

 commencement of the existing epoch, or modern formation. The 

 comparison and co-ordination of all the materials which have been 

 published for the ^.ast fifteen years, relating to Europe, Asia, the two 

 Americas and Australia, on the products of these phenomena, have 

 led us to the following results, which are solely the consequence of 

 facts, and may be regarded as independent of all theory on the origin 

 of the causes which produced them. It is, in other words, the most 



