580 



TEILOBITES OF UPPER CAMBRIAN. 



[Oh. XXYII. 



tween 1400 and 1500 species from the same Silurian and primordial 

 rocks of Bohemia.* 



In the primordial zone he discovered trilobites of the genera 

 Paradoxides, Conocephalus (Conocoryplie), Ellipsocephalus, Sao, Ario- 

 nellus, Hydrocephalus, and Agnostus. These primordial trilobites 

 have a j>eculiar facies of their own dependent on the multiplication 

 of thek thoracic segments and the diminution of their caudal shield 

 or pygidium. 



One of the " primordial " or Upper Cambrian Trilobites of the 

 genus Sao, a form not found as yet elsewhere in the world, has 

 afforded M. Barrande a fine illustration of the metamorphosis of 

 these creatures, for he has traced them through no less than twenty 

 stages of their development. A few of these changes have been 

 selected for representation in the accompanying figures, that the 



Fossils of the lowest Fossiliferous Beds in Bohemia, or " Primordial Zone " of 



Barrande. 



Fig. 66T. 



Conocoryphe striata. 



Syn. Conocephalus striatus, Emmrich. 



£ nat. size. Ginetz and Skrey. 



Fig. 668. 



Fk 



Paradoxides Itohemicus, Barr. 



About i natural size. Agnostus integer, Beyrich. Agnostus Bex, Barr. 



'Lowest Silurian beds" of Ginetz, Nat. size and magnified. Nat. size. Skrey. 



Bohemia. (Etage C of Barrande.) 



Fig. 670 



jSao hirsuta, Barrande, in its various stages of 

 growth. Skrey. 



The small lines beneath indicate the true size. In 

 the youngest state, a, no segments are visible ; 

 as the metamorphosis progresses, &, c, the body 

 segments begin to be developed ; in the stage d 

 the eyes are introduced, but the facial sutures 

 are not completed ; at e the full-grown animal, 

 half its true size, is shown. 



reader may learn the gradual manner in which different segments of 

 the body and the eyes make their appearance. When we reflect on 

 the altered and crystalline condition usually belonging to rocks of 



* Parallele entre les Depots Siluriens de Boheme et de Scandinavia 



