EOCKS OF BOHEMIA. 609 



But there is still another difficulty connected with the Grraptolites, 

 assuming the theory of Colonies to be true ; when the normal beds 

 of d 5 are of such a character as to contain Graptolites, these are 

 of different species from any found in the colonies. In the black 

 shales with Trinucleus Goldfussi &c. occurs a species of Diplograptus 

 different from any occurring in the colonies or in the beds of e 1. 

 Again, at Kraluv Dvur, near Beroun, in beds fairly high in d 5, 

 and which must surely be above some of the colonies, Dicellograptus 

 anceps occurs. Why do these not occur in the colonies also ? 



Although the shales of the colonies are not favourable for the 

 preservation of higher organisms, the limestone nodules are : one 

 would expect to find some of the characteristic Trilobites &c. of d 5 

 in these nodules, but nowhere is this the case. In Colonic Zippe, 

 however, occurring in the heart of Prague, M. Barrande records a 

 mixture of species of the second and third faunas occurring in the 

 same pieces of stone. The following list is given (Def. des Col. iv. 

 p. 115):- 



Second Fauna. 



Asaphus nobilis, Barr. I Phacops (Dalm.) socialis, Barr. 



Oalymene incerta, Barr. \ Trinucleus Groldfussi, Barr. 



Cheirurus insignis, Barr. 

 Arethusina Koninckii, Barr 

 Sphasrexochus mirus, Bei/r. 

 Phacops Grlockeri, Barr. 

 Leptasna euglypha, Balm. 



liaueri, Barr. 



Spirifer togatus, Barr. 



Third Fauna. 



Orthis nudus, Barr. 

 Atrypa reticularis, Linn. 



obovata, Sow. 



Rhynchonella monaca, Barr. 



daphne, Barr. 



sp. 



This colony, which is described as a mere lenticular fragment, is 

 not now exposed, and has not, as I am informed, been seen by M. 

 Barrande himself. I may remark that it is exactly in the line of 

 strike of the colony at Motol, and that the beds of d 4, in which 

 it occurs, are abont the horizon of the calcareous beds of Vraz 

 before described. May not the colony be a fault-breccia, consisting 

 of bits of limestone of d 4 and E, bound together by a calcareous 

 cement ? 



Another case of the coexistence of the two faunas at one horizon 

 is given by M. Barrande (Def. des Col. iv. p. 38) ; I shall treat of 

 this when describing Colonic D'Archiac. 



Besides the palseontological difficulties to be overcome in accepting 

 the theory of colonies, there are also stratigraphical ones. In ex- 

 amining Prof. Krejci's map of the neighbourhood of Prague, it will 

 be seen that the band d 5, in the neighbourhood of Beroun, where 

 there are no colonies, is very much thinner than near Prague, where 

 there are many ; and in examining the beds in the field this is found 

 to be chiefly due to the recurrence of great masses of grit in the 

 parts where the colonies occur ; whereas when they are absent the 

 beds of d 5 (whether or not they can be divided into an upper gritty 

 and a lower shale division, as proposed by Krejci) consist chiefly of 

 one series of shales and one of grits. But this is just the opposite 



Q. J. G. S. No. 144. 2 t 



