56 TRANSITION SERIES. 



Beginning with the animal kingdom, we find the four 

 great existing divisions of Vertehrata, Mollusca, Articulata, 

 and Radiata, to have been coeval with the commencement 

 of organic life upon our globe.* 



No higher condition of Vertehrata has been yet discover- 

 ed in the transition formation than that of fishes, whose his- 

 tory wdll be reserved for a subsequent chapter. 



The Mollusca,f in the transition series, afford examples 

 of several famihes, and many genera which seem at that 

 time to have been universally diffused over all parts of the 

 world. Some of these, (e. g. the Orthoceratite, Spirifer, 

 and Producta) became extinct at an early period in the his- 

 tory of stratification, whilst other genera (as the Nautilus 

 and Terebratula) have continued through all formations unto 

 the present hour. 



The earliest examples of Articulated animals are those 



mains preserved in the several series of formations, by introducing; over 

 each, restored figures of a few of the most characteristic animals and vege- 

 tables that occupied tiie lands and waters, at the periods in which thej were 

 deposited. 



* " It has not been found necessary, in discussing the history of fossil 

 plants and animals, to constitute a single new class; they all fill naturally 

 into the same great sections as the existing form?. — We are warranted in 

 concluding that tiie older organic creations were formed upon the same 

 general plan as at present. They cannot, therefore, be correctly described 

 as entirely different systems of nature, but should rather be viewed as 

 corresponding systems, composed of different details. The difference of 

 these details arises mostly from minute specific distinctions ; but somelimes, 

 especially among terrestrial plants, certain Crustacea, and reptiles, the 

 differences arc of a more general nature, and it is not possible to refer the 

 fossil tribes to any known recent genus, or even famil}'. Tlius we find the 

 problem of the resemblance of recent and fossil organic beings to resolve 

 itself into a general analogy of system, frequent agreement in important 

 points, but almost universal distinction of minute organization." — Phillips's 

 Guide to Geology, p. 61-63, 1834. 



t In tills great division, Cuvier includes a vast number of animals 

 having sott bodies, witliout any articulated skeleton or 8[)inal marrow, 

 such as the Cuttle-fish, and the inhabitants of univalve and bivalve 

 shells. 



