324 THE TRANSFORMATIONS OF THE ANIMAL WORLD 



not then yielded any organic remains, and were 

 called by English geologists "a barren grey-wack." 

 As against this, Barrande discovered in the Cambrian 

 strata of Bohemia a world of marine animals quite 

 different from the Silurian world. 



If we cast a glance on the geological structure of 

 the Prague basin, we shall notice that the primary 

 strata are disposed in concentric hollows, starting 

 from the crystalline schists which form their edges, 

 and designated by Barrande by the letter A. The 

 other more recent layers are modestly marked B 

 to H. The C layer is the home of the Primordial 

 fauna contained in the greenish brown schists which 

 crop up on both sides of the hollow in the two 

 celebrated villages of Skrej and Ginetz. 



The primordial fauna of Bohemia is, above all, 

 rich in Trilobites divided into seven different genera, 

 the most characteristic of which are the Paradoxides 

 and the Agnostus. The first named has a large 

 parabolic head, prolonged at the base and on the 

 sides by two long points, a thorax with many seg- 

 ments and a very small pygidium ; the second has a 

 cylindrical head and pygidium, joined by a tiny 

 thorax with two segments. The Agnostus and a 

 few other genera of the Primordial fauna are blind, 

 which leads to the belief that these Trilobites lived 

 in a relatively deep sea. There is, therefore, no 

 reason for wonder at the relative dearth in this 

 fauna of organisms other than Trilobites ; in fact, 

 they are restricted to a few Brachiopods, a Pteropede 

 Mollusc of pelagic habit, and to some remains of 

 Echinoderms of the group Cystoidea. 



