No. 2.] THE "colonies" of 3r. harrande. 199 



Stropliomena (Leptseua) eiigli/pha, Dalm. 



Cardiola internipta, Sow. 



Graptolites lohigerus, McCoy. (= G. Becki. Barr.) 



^Ussoni, Barr. 



priodon^ Barr. 



BoheniLcus, Barr. 



colonus, Barr. 



Roemer'i^ Barr. 



Rustrites peregrimis, Barr. 



To these I may add, CJimncograpsus teretiusculus, His., Grap- 

 tolites turrlcuhitus, Barr., G. Sedgwickii, Portl., Diploifrapsus 

 foliimi^ His., and Diplograpsus palmeus, Barr. 



Of the above eleven species enumerated by M. Barrande as 

 common to tlie colonies and the Lower Silurians of Britain, six 

 reappear in the Upper Silurian of Britain, and all are found in 

 the third fauna (Upper Silurian) of Bohemia. M. Barrande. 

 therefore, concludes that these species play the same part of pre- 

 cursors in the two countries compared ; and he believes that a 

 common centre of diffusion for these species must have existed 

 somewhere between Britain and Bohemia. It should be re- 

 marked, however, that of the above eleven species, four of the 

 Graptolites (viz. G. lohigerus, G jVilssoni. G. Bohemieus, and 

 Rastrifes j^eregrinus) are not known, as erroneously believed by 

 M. Barrande, to occur in the British Upper Silurian fseries ; nor 

 are any of the five species added by myself to the above list. It 

 should also be noticed that there is great doubt as to the pro- 

 priety of the introduction of Cardiola interrupta into the above 

 list as occurring in the Lower Silurian in Britain. On the con- 

 trary, it is becoming extremely probable that all the rocks in 

 which this fossil occurs in Britain are truly of Upper Silurian 

 age. 



. The following table shows the species of fossil.s w^iich are found 

 in the third fauna of Bohemia (Upper Silurian), but which 

 existed at an earlier date in the Lower Silurian of Britiin : — 



Crustaceans. 



Calijmene Blumenbachii, Brongn. 

 Staurocephalus Murchisoni, Barr. 



Cephalopods. 



Orthoceras anmdatum, Sow. 



