290 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



rande's able brochure entitled ' Parallele entre les Depots Siluriens 

 de Boheme et de Scandinavie,' 1856, it is stated that he finds few 

 or no common species among the six stages of Bohemia ; but if we 

 refer to his gTcat work on the Trilobites of that country, we shall 

 find the following facts contradictory of this statement (see p. 76 for 

 particulars). While the relations of his stages E and F (Upper 

 Silurian) are in no degree intimate, they still have the large number 

 of 14 Brachiopods and 8 Trilobites in common. Considering the 

 general scantiness of life in stage G (Upper Silurian), a near con- 

 nexion exists between stages F and G, because 22 fossils have found 

 a common home in them both, 16 being Trilobites. Here, then, are 

 44 recurrents, of an unmistakeable character, in only three stages. 

 Barrande * notices that 18 species of Trilobites inhabit two stages 

 indifferently; and this takes place in both Upper and Lower Silu- 

 rian ; the same species, however, are confined to their own divisions. 

 Cheirurus Sternbergii and Phaco^s fecundus are found in even four 

 stages (about equivalent to groups, as usually constituted), and 

 Phacops Bronni in three stages. The law of total extinction of life, 

 therefore, at the end of each subordinate period, as propounded by 

 M. Agassiz (none of whose words, however, should faU on careless 

 ears), is not in harmony with what we observe in any of the sedi- 

 mentary strata of the earth, except in Sweden, perhaps, according 

 to Angelin. It is not confirmed, but negatived, by such carefal 

 examination as the great Silurian areas of New York and Wales 

 have received. It is directly opposed to numerous facts gathered 

 from the whole series of sedimentary rocks, palaeozoic, mesozoic, and 

 tertiary. A regulated and slow extinction of vegetation has been 

 detected by Geinitz in the coal-measures of Saxony, with their five 

 zones of vegetable life. They contaia 156 species of plants. The 

 first zone has only 1 species out of 23 common to it and the second 

 and third ; but between the second and third there are 33 species in 

 common, with somewhat similar numbers common respectively to 

 the other zonesf. According to D'Orbigny X, all and each of the 

 mesozoic and tertiary strata of Prance, excepting the Few Bed 

 Sandstones, contain recurrent species, — ^the number, however, being 

 usually smaU. But in Kelloway Bock there are 25 " recurrents" in 

 255 species ; in Kimmeridge Clay, 16 in 183 ; in Miocene, 28 in 

 2726 ; and in Older Pliocene, 83 in 523. At p. 254 of the same 

 work, D'Orbigny states that Lima jprohoscidea lives in three stages — 

 the Inferior Oolite, Great Oolite, and Kelloway Bock, — and that cer- 

 tain 6 species inhabit the Kelloway Rock, Oxford Clay, and Coralline 

 Bag of the Jurassic period. In examining the ten great stages of 

 the Enghsh Oolite group, included between the Inferior Oolite and 

 the Upper Calcareous Grit, Dr. Wright finds 21 species of Echino- 

 dermata which recur 31 times, — 6 species making 3 appearances, 

 and 2 appearing 4 times §. Prof. J. Morris informs me that several 



^ Syst. Sil. Boheme, pp. 282, 283. 



t Pattison, ' The Earth and the Word,' p. 45. 



I Coiirs Elem. Paleont. vol. ii. passim. 



I Rep. British Assoc, 185G, p. 400. 



