peroneal muscles in birds. 1043 



Systematic Description. 



I have found thcat the following points are the most notable : — 



Peroneus longus. — Origin : " superficial," ^. e. forming a fairly 

 broad external sheet at the jjroximal end of the tibio-tarsal shaft 

 and arising chiefly from the head of the tibia and fibula and from 

 the fasciae over the knee-joint; "fascial," from the fascise of the 

 tibialis anticus on the one side and from that of the external 

 gastrocnemius and the underlying flexois on the other ; " deep," 

 from the side of the fibular shaft and the adjacent area of the 

 tibia on the opposite side from the oi^igin of the peroneus brevis. 

 The " fascial " origin is the least important morphologically and is 

 correlated with the strength and width of the muscle. " Anchor," 

 to the cartilaginous sustentaculum through which the flexor 

 tendons run at the tarsal joint. " Slip to III," the superficial 

 tendon which runs from the peroneus over the tarsal joint to join 

 the perforated flexor tendon of the third toe. 



Peroneus profundus. — Origin. Presence or absence of a bony 

 or fibrous bridge at the lower end of the tibio-tarsus. Tendon of 

 insertion. 



Relative size of the two muscles. 



RATIT^. 



S t r u t h i o n e s. Struthio. — The peroneus longus is enormous. 

 Superficial origin extends over to the femoro-fibular ligament and 

 the patella. Fascial origin present. Deep origin represented by 

 a separate head from the lower end of the fibula. Anchor is 

 broad and flat but short. Slip to III strong and rounded. 

 Peroneus brevis absent, but there is a short stout ligament which 

 may represent either the lower portion of the muscle, or, in my 

 opinion, more probably the ligament which ci'osses the tarsal 

 joint in Chauna. 



R h e 99. Rhea americana (two examples). — P. longus as in 

 Simthio, except that the deep origin extends for the greater part 

 of the length of the fibula. P. brevis absent, but tarsal ligament 

 present. 



Oasuarii. Casuarhis uniappendiculatus.- — P. longus enor- 

 mous ; superficial and fascial origins very extensive, deep origin as 

 in jRliea. Anchor short, very wide and partly in slips. Slip to 

 III stout. P. brevis absent but there is a stout tarsal ligament. 



DromcEXis novce-hollandice. — As in Casuarius, but P. longus not 

 quite so large. 



Apteryges. Apteryx (? species) (three examples). — P. longus 

 very large ; superficial and fascial origins good, but deep origin 

 very slight. Anchor broad and short ; slip to III a rounded 

 tendon. P. brevis very much reduced but present as a small fiat 

 tendon arising from a few muscular fibres and running in the 

 normal position under the slip to III. This is notably difi"erent 

 from the tarsal ligament in the other " struthious birds" and is 

 quite certainly a rudiment of the Pei'oneus brevis. 



