92 Mr. E. D. Cope on the 



lows : — In the depths of the sea, where a darkness approach- 

 ing zero, although not absolute, prevails, the animals living 

 there are either provided with highly developed organs of 

 sight, or the eyes are replaced by other organs which acquire 

 a considerable development. These organs, however, are 

 developed upon different parts of the body in accordance with 

 the external conditions and the mode of life of the animal, 

 which must be regarded as the primum movens of the whole 

 process of the degeneration of the one organ and the develop- 

 ment of the other. 



VIII. — On the Genera q/Felidse and Canidse. 

 By E. D. Cope. 



[Continued from p. 45. J 



Canidae. 



The range of variation presented by the species of Canidee 

 includes several generic divisions, recent and extinct. These 

 genera, however, are as closely intergraded as are those of the 

 cats ; and their definite characters are subject to occasional 

 failure from abnormal variations. These, however, are not 

 so frequent as to invalidate the classification to which they 

 form the exceptions. 



The Canida3 appeared in the Upper Eocene period ; and the 

 genus Canis was well represented by species in the lowest 

 Miocene in Europe and the United States. The other genera 

 are represented by fewer species ; and many of them are 

 extinct. The foxes ( Vuljpes) are the most numerous of them ; 

 and but few extinct species of them are known. America 

 presents us with the greatest variety of genera, as Enhydro- 

 cyon, Temnocyon, and Palaiocyon extinct, and Icticyon, extinct 

 and recent. Speothus, extinct in America, still exists in 

 Asia. 



The most complete catalogue of the species of Canidse is 

 that of Dr. Gray. In his work the author brings together 

 observations of various naturalists, and adds a number of his 

 own. He admits a large number of generic divisions ; but 

 many of these, like those of his Felidas, are simply founded 

 on specific characters. A few good genera, however, exist ; 

 and a synopsis of their characters is given below. The genus 

 Megalotis is here excluded from the Canidas on account of the 



