Number of Animals in Geological Times. 357 



of Crustacea could be collected anywhere on a shore of equal 

 extent to that of the white chalk of Sussex, as Dr. Mantell has 

 uncovered in the vicinity of Lewes. For a comparison of the 

 Crustacea of the oolitic period, I would only refer the sceptic to 

 the monograph of the Crustacea of Solenhofen by Count Minister, 

 who has figured from that single locality more species than are 

 known in the whole basin of the Mediterranean, excluding the 

 minute species which have not yet been sought for among the 

 fossils. 



In earlier geological ages, during the deposition of the coal 

 and other palaeozoic rocks, the class of Crustacea presents a very 

 different character. The gigantic Entomostraca and the extinct 

 family of Trilobites take the place of the lobsters and crabs of 

 later periods. But palseontological works illustrating the fossils 

 of Sweden, Russia, Bohemia, England and France, have made 

 us acquainted with as great a variety of species of those families 

 as are found of the later representatives of the class in more 

 modern deposits. So that among Articulata, the class of Crus- 

 tacea may be said to have been at all periods as largely repre- 

 sented, and to have shown as great a variety of forms, as occur 

 anywhere within similar limits in the present time. 



The carcinological fauna of the whole Indian Ocean scarcely 

 exceeds in variety or number of species that of Bohemia alone, 

 as it is now known by the admirable investigations of M. Barrande. 

 From their minuteness and general structure, insects might 

 be excepted in such a comparison without affording a sufficient 

 argument against the view I have taken of the subject, even if 

 insects had nowhere been found in large numbers in a fossil state ; 

 for it must be plain that their preservation requires more favour- 

 able circumstances than the preservation of other animals more 

 largely provided with solid parts. But though the fossil insects 

 have not been sufficiently investigated in all geological forma- 

 tions, have we not several examples which show r that in some 

 geological periods, at least, they were as numerous as in the 

 present day ? The beautiful monograph of Behrens, of the in- 

 sects which occur in amber, shows how varied these animals 

 were during the period of the formation of that gum ; and the 

 unparalleled investigations of Professor Oswald Heer upon the 

 insects of OEningen and Radoboj have furnished us with means 

 of comparisons which show that, during the deposition of the 

 Molasse of Switzerland, the insects were as numerous and as 

 diversified there as they are anywhere in our day within similar 

 boundaries. And the fragmentary information which we already 

 possess upon the insects of Aix in Provence, and those of (Enin- 

 gen, will justify the expectation that insects will finally be found 

 very numerous in all the geological periods from that of the 



