450 



PRIMORDIAL GROUP OF BOHEMIA. [Ch. XXVII 



Bohemia. — M. Barrande, in bis admirable monograpb on tbe Paleozoic 

 rocks of Bobemia, bas laid much stress on tbe distinctness and isolation 

 of wbat be calls tbe "Protozoic schists," which attain a thickness of 120C 

 feet, and lie at the base of the whole Silurian group, as defined by him. 

 These schists have no limestone associated with them, and are regarded 

 by M. Barrande as contemporaneous w^ith the " Lingula Flags" of N. 

 Wales. So far as he has yet carried bis researches, this " primordial 

 fauna," as be designates it, has yielded scarcely any other fossils than 

 Trilobites, tbe other animal remains consisting of a Pteropod, some Cys- 

 tideae, and an Orthis, all of new and pecubar species. Of tbe Trilobites, 

 even tbe genera, with tbe exception of one (Agnostus^ figs. 615 and 616). 

 are peculiar. These genera are Paradoxidcs (see fig. 613), of which 

 there are no less than twelve species, Conoccphalus (fig. 614), Ellipso- 



Fossils of the loioest Fossiliferous Beds in Bohemia, or " rrlmorcUal Zone " of Barrande. 

 Fig. 613. Fi>. fiU. 



Conocepluilu.s siri(itit-% Emmrich. 



^ nat. size. 



Ginetz and Skrey. 



615. 



Fisr. 616. 



Affnostus integer, Beyricb. 

 Nat. size and magnified. 



Agnostus Rex, Barr. 

 Nat. size, Skrey. 



Faradoxides BoJiemicus, Barr. 



About one-third natural size. 

 "Lowest Silurian Beds" of 

 Ginetz, Bohemia. 



Y\^' ciV'^" ^' cephalus., Sao (fig. 617), Arionellus, and 



^] c^^^^^ Hydrocephalus. They have all a facies of 



their own, dependent on tbe multiplication 

 of their thoracic segments, and tbe dimi- 

 nution of their caudal shield or pygidium. 

 All the Bohemian species differ as yet 

 from any found in England, which may 

 be owiug chiefly to the very small num- 

 ber as yet known in Great Britain ; or it 

 may be due entirely to the influence of 

 geographical causes. It seems, neverthe- 

 less, to confirm the view here taken of tbe 

 "primordial zone" being characterized 



by fossils distinguishable from the Llandeilo, or Lower Silun'an group ; 



because the other and higher Silurian formations of Barrande have each 



of them many species in common with tbe successive subdivisions of the 



British series. 



Sao Mrsuta, Barrande, in its various 

 .stages of growth. Skrey. 



The small lines beneath Indicate the 

 true size.' In the youngest state, a, 

 no segments are viisible ; as the meta- 

 morphosis progresses, &, (?, the body 

 segments begin to be developed; in 

 the stage d t.Iie eyes arc introduced, 

 but the facial sutures are not com- 

 pleted ; at e the full-grown animal, half 

 its true size. Is shown. 



