186 Report of the State Geologist. 



The uacertainty grows in measure as we approach the more and 

 more ancient deposits. The fossils of the primary epoch which 

 are known at the present day are, it is true, very numerous, yet 

 various circumstances should convince us that the palaeozoic 

 faunas are still less completely known than those of the Sec- 

 ondary, and still more, those of the Tertiary epochs. The pri- 

 mary strata have naturally undergone more changes than the 

 others; erosions at successive epochs have removed considerable 

 extents of the deposits, and displacements have frequently modi- 

 fied the nature of the rock and occasioned the disappearance or 

 alteration of the fossils contained in it ; so much so, that for 

 many years primary fossils in a good state of preservation have 

 been found only in 'few localities; it is only recently that the 

 discoveries made in America, Russia, India, etc., have made pos- 

 sible the definition of the analogies and differences between the 

 faunas of those countries and those of western Europe already 

 known. Furthermore, many groups which had appeared at 

 remote epochs were represented at first by individuals few in 

 number and of a lower organization, the remains of which are 

 rarely found. 



The first fauna. — As has been said, uncertainty increases as 

 we approach more and more ancient deposits. It reaches the 

 maximum when the question concerns the most ancient fossilifer- 

 ous beds, those from which we might hope to draw some knowl- 

 edge regarding the actual origin of organisms. The earliest depos- 

 its in which fossils are positively known to occur are the Cambrian. 

 The fossils found there are a few Mollusks, belonging to three 

 classes of the group ; Trilobites,' belonging to diverse families 

 {ParadoxidcB^ Olenidm) ; Crustacea {Leperditia, Hymenocaris) ; 

 Brachiopoda {Lingulidce, DisoinidcB, Orthis), some Cystids, some 

 Hydroids {Dictyonema), Medusse, Hexactinellid and Tetractinellid 

 Sponges {ArchcBosGyphia^ Protospongia). We must add also the 

 impressions of organisms whose determination is uncertain 

 {OidJiarrhia^ JEophyton, BilobiteSy Fucoides^ etc.). This . fauna, 

 rich • both in genera and in species, embraces a small nurdber 

 of groups, which in reality are not high types of the animal 

 kingdom ; but nevertheless they are far from representing the 

 primitive ancestors of animals. The Brachiopoda, in particular, 

 are organisms which must have undergone an extremely compli- 



