BRONN ON PAL^ONTOLOGICAL STATICS. 45 



I. Diu'ation of Sjjecies. 



There can be no doubt that fossil species pass from one formation 

 into another, from one period into the next, and in rare cases even 

 into a third period, if we indeed allow the present creation to rank as 

 a VI. period, even although half the instances of such transitions may 

 depend on erroneous determinations. No further proof of this need 

 be required, than that the most experienced zoologists and botanists, 

 and even the most decided opponents of this view, Agassiz and D'Or- 

 bigny, after examining the original specimens adduced in proof, have 

 themselves unconditionally admitted it. For instances of the occur- 

 rence of identical species in two neighbouring formations, we will here, 

 to avoid prolixity, refer to the original text, where they are more 

 fully detailed, and confine ourselves to some of the more important 

 proofs. Almost everyone knows certain forms of Terehratula bipli- 

 cata from the oolite and the chalk, which cannot be distinguished from 

 each other in any constant manner. Edward Forbes declares ex- 

 pressly that he has found the TerebratiiJa caput-sei-pentis of the white 

 chalk, of the upper tertiary strata, and the present seas ; and the 

 Echinocyamus pusillns in the eocene, miocene, pliocene strata and 

 living, entirely identical. Ehrenberg mentions — even after the ex- 

 clusion of all the tertiary strata erroneously joined to the chalk — a still 

 very considerable numl3er of infusoria and foraminifera as occurring 

 in the chalk, in the tertiary formations and living; and D'Orbigny, 

 in agreement with this, declares* that he cannot distinguish the 

 Dentalina communis and Rotalina umhilicata of the Paris white chalk, 

 either from the tertiary or from the living species of the Mediterra- 

 nean, and in regard to the latter especially, that after the most mi- 

 nute comparison he cannot find any distinction. He himself quotes 

 five cephalopods (^Ammonites latidorsatus,A. Mayoranus,A. injlatus, 

 Hamites armatus, Turrilites Bergeri) and three foraminifera {Den- 

 talina sulcata, Mai^ginulina compressa, Cristellaria rotula) in the 

 greensand (gault) and in the chalk (in r and /") . Agassiz himself 

 cites liamma elegans in t, u, v, w, Odontasjns contortidens in u,v, Wy 

 and Cytherea {Lucind) leonina in u, v. That a great number of ter- 

 tiary species pass into the present creation, is not only admitted by all 

 palaeontologists with two or three exceptions, but has also been spe- 

 cially proved by us in our review of Agassiz' memoir " Sur les especes 

 reputees identiquesf," and among other things by showing partly 

 that the specific distinctions which Agassiz adduced between speci- 

 mens of certain species from the two positions, and partly that the 

 identity of geological position which he assumed for the genuine 

 Cyprina Islandica in Sicily as quaternary instead of tertiary, did not 

 exist. There are tertiary and more recent strata where the number 

 of species that continue into the living creation amounts to 0*04 — 

 0-20-0-50— 0-60— 070— 0-80— 0-90— 0-95— 0-99 — 1-00, with- 



* Memoires de la Societe Geologiquc, iv. 13, 32. 

 t Jahrbuch, 1816, p. 250, seq. 



