CAMBRIAN" FAUNA. 135 



Archaeospherina ? Surely it could not have been that there was 

 such a disposition of the remains as to leave nothing but these two 

 forms belonging to the lowest type. It appears far more plausible 

 to assume with those who uphold the mineral nature of Eozoon 

 and Archaeospherina that we have no traces of this ancient pre- 

 Cambrian fauna remaining, and that, consequently, the destruction 

 was complete. How far back beyond the Laurentian the root of 

 tlie present existing chain of organisms may have extended it is 

 impossible even to conjecture. 



Cambrian Fauna. — It is certainly a surprising fact, whichever 

 way it be considered, that, with the formation bringing the first 

 unequivocal evidences of organic life, we should meet with that 

 multiplicity and variety which characterise the faunal assemblage 

 of the Cambrian period. Most of the greater divisions of the ani- 

 mal kingdom, possibly not even excepting the vertebrates, were 

 there represented, and most of these already in the lowest or 

 oldest dejiosit — protozoans, coelenterates, echinoderms, worms, 

 articulates, and moUusks. And more than this, some of these 

 groups were already represented by a full, or nearly full, com- 

 plement of the orders that have been assigned to them by natu- 

 ralists, and which include all the various forms that have thus 

 far been discovered as belonging to the groups. Thus the Cam- 

 brian echinoderms are represented by forms belonging to three 

 out of the six usually recognised orders — the Cystidea, Crinoidea 

 (ocean-lilies), and Asteroidea (star-fishes). The last two have repre- 

 sentatives living at the present day, whereas the former is entirely 

 extinct. We have here, then, the most ancient ocean-lily and star- 

 fish (Palasterina), and it is interesting to note what distinct rela- 

 tions these two forms hold to their modern representatives. While 

 the Crinoidea attained their maximum development in the seas of 

 the Paleozoic period — Silurian, Devonian, and Carboniferous — since 

 which time they have been pretty steadily declining, until at the 

 present moment they are represented by scarcely more than a half- 

 dozen distinct generic types, the Asteroidea have been just as stead- 

 ily increasing, and, indeed, attain their maximum development in 

 the modern seas. 



It may appear at first sight anomalous how two groups, so widely 

 dissimilar from each other, and having such varying developments, 

 should have appeared simultaneously in the same period of the 



