80 Featherstonhaugh? s Geological Report. 



earth, as it gradually emerged from the water, and approached 

 more to the present order of nature. Although we cannot say 

 that we have any evidence in the rocks of the germs of organi- 

 zation, yet the fossils of the first great transition group, as it 

 has been called, appear to be the types of what have suc- 

 ceeded to them. The Crustacea of that period naturally fall 

 into the class of their order which has been established from 

 recent genera, as well as the prodigous abundance of madre- 

 pores and corallines, whose structures in those ancient geologi- 

 cal times were apparently reared with the same instinctive 

 designs, and principally by the same genera of which we have 

 evidence in the reefs of eastern Polynesia. 



The crinoidea also, or encrinites, now nearly extinct, are 

 abundant. In these ancient times this family, as if less ex- 

 posed to destruction from the existing state of organization in 

 the then seas, had their soft parts but slightly protected, whilst 

 in the succeeding formations in the older groups, where the 

 predacious classes increase in number, they are much better 

 secured. The sole species now existing, the pentacrinite, 

 agrees with these last in its more perfect osseous structure, which 

 still seems to have been insufficient to protect the family. 



The beds of this group also contain fine specimens of another 

 family which appears to have become extinct at an early period 

 of the secondary rocks. These belong to the genus orthocera, 

 a long straight fossil, consisting of various chambers, with a 

 siphon or tube, by the aid of which the cephalopodous animal 

 is supposed to have been able to pass from the top to the bot- 

 tom of the sea at its pleasure ; resembling in this the ammonite, 

 another concamerated shell, not straight but spiral in its form, 

 and which, with other concamerated shells, is found in the 

 limestones of this lower group. 



The trilobite, a singular marine crustaceous animal, is a fos- 

 sil almost peculiar to the period of this group, since it appears 

 to have become extinct in the early part of the deposition of 

 secondary rocks. Some of the lower slates are covered with 



