48 IMPORTANCE OF STUDY OF FOSSILS IN ZOOLOGY. 



ocean, or live on its borders, the various tribes of Fishes, Mol- 

 lusca, Crustacea, Worms, and Zoophytes, the proportion which 

 yet remains to be discovered is doubtless very large. Even on the 

 coasts that have been most thoroughly explored, new species are 

 continually being discovered; and these are often very dissimilar in 

 form to any previously known, presenting both to the Naturalist 

 and to the Physiologist many points of the greatest interest. 



28. But it is not only in the extension of our knowledge of 

 existing species, that much yet remains to be accomplished, before 

 the foundation of a Natural Classification can be regarded as 

 securely laid. No system can be complete, which does not 

 include those that formerly tenanted the globe, as well as those 

 that at present inhabit it. A very slight knowledge of Fossil 

 Zoology is sufficient to convince the Naturalist, that the animals 

 which peopled this earth in its earlier ages were constructed 

 upon the same general principles, as those now existing upon its 

 surface ; so that it is safe to reason as to the portions of their 

 structure that are not preserved (which is generally the case 

 with regard to their softer organs), by comparing those which 

 are with the corresponding parts of animals now living. Fre- 

 quently it is found that peculiar forms of structure, which are at 

 present exhibited in but few and comparatively insignificant 

 tribes, were formerly displayed in races, which must have pos- 

 sessed, from their number and power, the predominance over all 

 the rest at that epoch. This is the case, for instance, in regard 

 to the Saurian (lizard-like) Reptiles, and the enamel and bony- 

 scaled Fishes. Hence we should not understand the true station 

 of these as natural groups, from those species alone which at 

 present exist ; these being only the few and feeble remnants, as 

 it were, of the numerous and gigantic races which they represent. 

 Still more frequently does it happen, that gaps or deficiencies 

 exist in the groups, which are formed by bringing together exist- 

 ing animals alone ; and that these groups are completed, and are 

 connected with others apparently far removed from them, by 

 species which existed in ages long since past, and whose fossil 

 remains are preserved to us, as if for the very purposes of the 

 Zoologist. Thus, for example, the order PACHYDEBMATA, in the 



