MAMMALIA 297 



solution of gelatine, and thus their original tenacity may 

 be restored * Petrified fossils need no such treatment ; they 

 are usually harder and more durable than the original bone 

 itself. 



The interpretation of such fossil remains requires a com- 

 parison of them with the corresponding parts of animals now 

 living, or of previously determined extinct species. In the case 

 of the vertebrate animals, such comparison is limited to the 

 osseous and dental systems. The interpretation of a vertebrate 

 fossil, therefore, presupposes a knowledge of the various modi- 

 fications of the skeleton and teeth of the existing vertebrate 

 animals ; and the more extensive and precise such knowledge 

 may be, the more successful will be the efforts, and the more 

 exact the conclusions, of the interpreter. 



The determination of the remains of quadrupeds is beset, 

 as Cuvier truly remarks, with more difficulties than that of 

 other organic fossils. Shells are usually found entire, and 

 with all the characters by which they may be compared with 

 their analogues in the museums, or with figures in the illus- 

 trated books, of naturalists. Fishes frequently present their 

 skeleton or their scaly covering more or less entire, from which 

 may be gathered the general form of their body, and frequently 

 both the generic and specific characters which are derived from 

 such internal or external hard parts. But the entire skeleton 

 of a fossil quadruped is rarely found, and when it occurs, it 

 gives little or no information as to the hair, the fur, or the 

 colour of the species. Portions of the skeleton with the bones 

 dislocated, or scattered pell-mell — detached bones and teeth, 

 or their fragments merely — such are the conditions in which 

 the petrified remains of the mammalian class most commonly 

 present themselves in the strata in which they occur. 



• The writer's experience of this effect led him to suggest the application of 

 a similar process to the long buried ivory ornaments from the ruins of Nineveh 

 in the British Museum ; it proved successful. 



