IN MODERN SCIENCE. 



129 





blame. In connection with his great and class- 

 ical work on the Silurian fossils of Bohemia, it 

 has been necessary for him to study the similar 

 remains of every other country ; and he has 

 used this immense mass of material in prepar- 

 ing statistics of the population of the Palaeozoic 

 world more perfect than any other naturalist 

 has been able to produce. In successive me- 

 moirs he has applied these statistical results to 

 the elucidation of the history of the oldest group 

 of crustaceans — the trilobites — and the highest 

 group of the mollusks — the cephalopods. In 

 his latest memoir of this kind he takes up the 

 brachiopods, or lamp-shells, a group of bivalve 

 shellfishes very ancient and very abundantly 

 represented in all the older formations of every 

 part of the world, and which thus affords the 

 most ample material for tracing its evolution, 

 with the least possible difficulty in the nature 

 of "imperfection of the record." 



Barrande, in the publication before us, dis- 

 cusses the brachiopods with reference, first, to 

 the variations observed within the limits of the 

 species, eliminating in this way mere synonyms 

 and varieties mistaken for species. He also 

 arrives at various important conclusions with 

 reference to the origin of species and varietal 



