1894.] 



MYOLOGY OF RODENTS. 



267 



In the Octodontidae there are always four tendons to the digits 

 and one to the thumb. There are also four luinbricales. 



In the Hystricidse no slip is sent to the thumb in Hystrix and 

 Sphingurus, but Mivart describes the muscle as dividing into five 

 tendons in Erethizon dorsatus l . 



Kg. 3. 



RuDI . POL 



Left fore foot of Sphingurus prehensilis (superficial dissection). 



There were three lumbricales in Hystrix and Erethizon 1 , four in 

 Sphingurus. 



The Chinchillidse have no slip to the thumb and four lumbricales. 

 In the Dasyproctidae there is no slip to the thumb aud three 

 lumbricales. In the Caviidae the arraugement is the same. 



In the Sciuromorpha there are four tendons in Sciurus, Pteromys, 

 and Arctomys, but Xerus and Castor have five. 



The number of the lumbricales in Rodents seems liable to 

 individual variation, as a rule the one on the ulnar side is larger 

 than the rest and rises from the front of the flexor profundus 

 before it divides. 



Pronator Quadratus. — This muscle is usually well marked, 



1 P. Z. S. 1882, p. 271. 



