1894.] 



MYOLOGY OF RODENTS, 



267 



In the Octodontidse there are always four tendons to the digits 

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



In the Hystricidae no slip is sent to the thumb in Hijstrix and 

 Sphinfjuriis, but Mivart describes the muscle as dividing into five 

 tendons in Erethizoa dorsatus \ 



rig. 3. 



Ruoi . POL .- 



FLEX. iOB 



Rao . . 



V\%\. 



Left fore foot of SpMngurus prehensilis (superficial dissection). 



There were three lumbricales in Hystrix and Ereth{zon\ four in 

 Sphingurus. 



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

 In the Dasyproctidffi there is no slip to the thumb and three 

 lumbricales. In the Caviidse the arrangement is the same. 



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

 and Arctomys, but Xenis and Castor have five. 



The number of the lumbricales in Eodents 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. 



