160 VIEW OF THE EXTINCT FAUNA OF BRAZIL. 



suppose that an organ should lose its function and significance 

 precisely at the point where it is mostperfectly developed. We 

 cannot doubt, therefore, thatthepowerful claws with which we 

 find Megalonyx and Megatheriam armed, have had their use. 

 We may even conclude with certainty, that the habits of 

 the animals were closely connected with these organs, and 

 that their very existence depended on them. Now, as we 

 only know of two uses for strong claws in Mammalia, dig- 

 ging and climbing ; and as these two purposes require dif- 

 ferent anatomical arrangements ; it will not be very difficult 

 to decide for which of them the powerful organs in the ex- 

 traordinary creatures we are considering were intended. We 

 find among the animals the most perfectly organized with 

 respect to burrowing, such as Talpa, Spalax, Condylurus, 

 &c., that the claws are strong, long, broad, and nearly of 

 equal size, that all the digits are provided with similar claws, 

 and are extended in almost the same plane as the hand, 

 which is of considerable breadth. Next to moles, the best 

 diggers or burro wers are found in the order to which Mega- 

 lonyx belongs, especially in the family Dasypiis\ but the 

 different species of that genus are not all equally well pro- 

 vided in this respect. The best diggers are the Cahassous 

 (Xe?iurus, Priodon), among which we again recognize the 

 same characters as in the moles ; a broad hand, all the digits 

 provided with claws, very broad, and nearly equal. In the 

 Euphractus the hand is somewhat smaller, as are also the 

 claws, although their number remains undiminished ; conse- 

 quently, the species of this family cannot compete with the 

 former as burrowers- In the proper Dasypus, the number of 

 digits provided with claws is reduced to four ; and they are 

 so inferior to the first described, in the faculty of digging, 

 as to avail themselves, for the most part, of the burrows the 

 others have excavated. 



Let us next examine the plan of construction of the hand 

 in those animals that use their claws as hooks to climb with. 

 We find the most perfect form of this kind in the sloth. Its 

 claws are extraordinarily long, curved and compressed : they 

 are so articulated as to be incapable of extension, whence, 

 during the animal's repose, they are bent under the fore 

 foot ; and at the utmost, can only be extended so as to form 

 a right angle with it. Again, not more than three digits in 

 some, and two in others, are furnished with equal claws ; and 

 the hand is small. We thus see, that hands adapted for 

 climbing and burrowing, are constructed on two almost op- 

 posite plans ; let us then examine to which of them the Me- 

 galonyx bears the most resemblance. 



