RESULTS OF PAL^EONTOLOGICAL RESEARCH 27 



perfect forms with well-developed eyes and with the 

 faculty of rolling themselves tip, obtain preponder- 

 ance ; the Cephalopods, certainly only a branch of the 

 Nautiloids, become plentiful and of many types ; 

 the Ammonites are almost entirely absent their 

 time has to come. 



The shells of the Orthoceras forms are somewhat 

 convoluted. 



The Crinoids (rare in the Cambrian formation) 

 become very numerous; to them are added, but at 

 first sparsely, the two new classes of Echinidae, the 

 sea stars, and sea urchin. 



The Bryozoa are also noticed, but they are far 

 from having the importance they later acquired. 



In short, we understand why in view of the first 

 Vertebrates and land plants, in view of so many new 

 orders and families appearing within classes already 

 existent, and in view of the great number of families, 

 genera, and species into which other classes and 

 orders, as it appeared, simultaneously and surprisingly 

 quickly (' explosively ') split themselves up a new 

 ' creation/ the Silurian, can be spoken of. 



We cannot go through the formations separately, 

 but confine ourselves here once more to the deter- 

 mination of the chief results which are necessary to 

 further explanations. 1 



1 E. Kayser (Lehrbuchder Geolog. FormationsJcunde), after discussing the 

 separate formations, gives a good palaeontological purview, to which the 

 reader is referred. K. von Zittel's Handbuch der Paldontologie, Munich and 

 Leipzig, 1876-1893 (5 vols.),goes more into detail. Regarding the history 

 of the Vertebrates the best information is given by E. Frieherr Stromer v. 



