XXVI 



FACTS AND OBSERVATIONS. 



trace them to their several birthplaces, and so to point out the relations they establish between 

 Bohemia and those birthplaces *. 



It is an accepted truth that the earliest bed in which any form of life is found is its birth- 

 place (a word convenient and short), although an occasional correction may become necessary. 



Thus, until better taught, we take a fossil of any of the Bohemian faunae E, F, G, H, to have 

 first existed in Wales, if we find it there in Llandeilo or Caradoc and nowhere else, unless actually 

 seen. We know how a change of residence can be effected. 



Bohemia has vital relations of this kind with many countries, but none so remarkable as those 

 lying on the edge of the Atlantic, or on the Mediterranean. With these and with the other areas it 

 is connected by means of mollusks which are known only in the two areas concerned (save the uni- 

 versals) a fact which gives precision and speciality to the connexion. We will enter into the 

 following particulars 1 



Amorphozoa. Of the five species of Stromatopora in Bohemia, only one occurs elsewhere ; and 

 that is in Lake Huron, in the Hudson- River group, while the Bohemian species is Upper- Silurian 

 (E. e. 2). Its birthplace seems to have been in the distant West. The Ischadites Kcenigii is in 

 Shropshire in Llandeilo as well as in Upper Silurian; in Bohemia it is in E. e. 2, and is not a 

 native. 



Ccelenterata. Adding the Crelenterata lately received from M. Barrande to those already in 

 hand, we at present only know of twenty species in Bohemia ; of these, twelve are foreign and eight 

 native. Of the foreign, three are everywhere (in Bohemia &c.) on the same horizon, and nine vary 

 in this respect, eight being in the Llandeilo and Caradoc beds of Britain, and one Lower- Silurian 

 both in Canada and Esthonia the whole of them being Upper-Silurian in Bohemia, where they are 

 therefore strangers. The native Bohemians are all of the upper zones. The particulars of these 

 statements are easily found in the ' Thesaurus.' 



Of the seventeen species of Bohemian Echinoderms which, through the kindness of M. Barrande, 

 are found in the ' Thesaurus/ all, excepting two, belong to the earlier part of the Lower Silurian 

 stage ; for this reason, as well as because they are nowhere seen in any other stage, these Crinoids 

 are probably natives. We cannot at present determine the place of first appearance in the cases of 



* It is easy to see that several useful inferences might flow from the facts, gathered into a series of tables, of 

 which the imaginary one subjoined might be the first (it gives the native and foreign species of all the orders, for the 

 whole area concerned, France, Britain, Canada, &c. ; other Tables might do the same for the separate stages ; others, 

 again, might show the zoological relations of area with area, American, Australian, European : a very little zeal 

 might here open a wide door) : 



A Form of Table exhibiting the Native and Foreign Fauna of certain Silurian Districts. 



It should be here stated that the change of horizon often effected by species is called " recurrence ; " and it is 

 greatly facilitated by the power that species possess of living on several kinds of sediments, and by migration subjects 

 to be treated on in the sequel. 



