412 MR. ST. GEORGE MIVART AND DR. J. MURIE [June 26, 



and Rabbit (according to our dissections) this muscle has but a single 

 head of origin, which arises from the upper portion of the tibia, thus 

 differing widely from the condition present in the Agouti and Guinea- 

 pig. 



Meckel * says that in the Porcupine it is united with the extensor 

 proprius hallucis ; but in our specimen that muscle existed in addi- 

 tion to the double tibialis anticus. He further observesf that in the 

 Marmot the tibialis anticus is divided into a large tibial and a small 

 peroneal head ; but there is no mention of any origin from the femur. 



The extensor longus digitorum arises by a very broad tendon from 

 the femur, just external to the long tendon above-mentioned of the 

 tibialis anticus. Proceeding downwards, it divides into three tendons, 

 which are respectively inserted into the second phalanges of the 

 only digits present, i. e. second, third, and fourth (figs. 4 & 5, E. I. d.). 



The Guinea-pig appears to have a similar disposition in this 

 muscle, although in one foot we noticed the inner tendon bifurcating, 

 the double tendon going to the same digit. In the Hare and the 

 Rabbit it arises by a long, round (instead of flattened), strong tendon 

 from the front of the outer condyle of the femur ; this tendon then 

 runs through that groove which the femoral tendon of the tibialis 

 anticus traverses in the Agouti. It divides into four tendons, which 

 are inserted into the four digits ; that to the index or inner toe sends 

 a branch to the third digit. 



The extensor proprius hallucis is rather a delicate muscle (fig. 5, 

 E.p.h.). It arises from the upper two-thirds of the fibula and 

 interosseous membrane, gives origin to a slender tendon, which ends 

 in an insertion into the second phalanx of the index. The same in 

 Guinea-pig. 



This muscle is absent in the Hare and Rabbit. 



The muscular fibres of the extensor brevis digitorum extend for- 

 wards over about the posterior third of the metatarsal bones, arising 

 also from the dorsum of the tarsus above the cuboid and os calcis. 

 These give rise to two tendons, which are inserted respectively into 

 the two inner toes, namely the index and third digits, joining at the 

 side the tendons of the long extensors. 



It is the same in the Guinea-pig ; but this muscle is wanting in 

 the Hare and Rabbit. 



Peroneus longus. This is a small muscle arising, as in Hyrax%, 

 from the head of the fibula, on each side of the lateral ligament ; so 

 that at first sight it appears as if it arose by a tendon from the femur, 

 like the extensor longus digitorum. Passing down behind the ex- 

 ternal malleolus it sinks beneath the foot, passing through the groove 

 on the outer side of the cuboid, crosses the sole deeply (hidden by 



* Loc. cit. p. 410. t Ibid. p. 411. 



J See P. Z. S. 1865, p. 348, and fig. 12. p. 349, where, by an error of the 

 artist (pardonable by reason of the very deceptive appearance of the external 

 lateral ligament), the peroneus longus has been figured as if arising by tendon 

 from the femur, which, as may be seen in the description, it does not ; while 

 the extensor longus digitorum. which really does arise from the femur, is repre- 

 sented as coming only from the tibia. 



