644 EKPTILES AND AMPHIBIANS. 



Valley, as first pointed out by Agassiz for Turtles, and afterwards di- 

 vided by Cope, into an Eastern, Southern, and Western fauna. 



Finally, in regard to classification, the study of these animals has been 

 rendered needlessly complicated. Naturalists have seemed so eager to 

 append their names to a new species that, instead of examining to see 

 what others had done before them, they affixed a new name to a large 

 per cent , at least, of the animals met. The truth of this statement is 

 evident from the abundant synonyms by which nearly all these animals 

 are known. In some cases again, the most careful and conscientious observ- 

 ers have been misled, and considered varietal differences specific charac- 

 istics. Such a principle followed out in regard to the human race would 

 give us numerous species of men founded on as valid grounds as have 

 been many of the species of animals. Moreover, in regard to the separa- 

 tion of these animals into genera, families, sub-orders, etc., naturalists 

 have changed each others names and arrangement, often for better, but 

 too many times apparently for the sake simply of a change, and to the 

 disadvantage of science. 



In selecting marks of species, families, and orders, much difficulty must 

 be experienced. To any one who has made a careful and thoughtful 

 study of osteological characters, these, though among the best, are insuf- 

 ficient. Thus the bones of the same animal vary, not only in the extent 

 of ossifica,tion, but in number with age. Nor are the anatomical relations 

 of the soft parts any more valid. Let a person examine the structure of 

 a frog and tadpole, and he would unquestionably pronounce them to be 

 distinct species. On the other hand the teeth, their shape, presence or 

 absence, the matter of having a grooved or hollow poison fang, indicate a 

 habit of the animal, and are, to a certain extent at least, valuable grounds 

 of classification. The same remark will apply to the presence or absence 

 of a tongue in the Amphibians, its shape and attachments, and whether 

 protrusible or not, so as to become an instrument of prehension. In a 

 similar manner the palmation of the toes indicating an aquatic ani- 

 mal, and the dilatation of the tips showing an arboreal habit, the pro- 

 jecting rostral in Heterodon, the soft shell and prolonged nostrils in the 

 Trionychidse, the presence of parotoids, the granulation of the abdomen, 

 the covering of the head, the scales whether carinate or not, the presence 

 of spines or thorns, and femoral pores, as well as the transverse lamellae 

 seen on the feet of Anolis, seem to be tolerably constant and consequently 

 valuable in classification. These should be combined with osteological 

 and other characters carefully used, and also taken with a diligent study 

 of the animal's habits, and thus in time we may hope to get a valuable 

 and permanent arrangement. Until such a redistribution can be made, 



