PERONEAL MUSCLES IN BIRDS. 1057 



In the case of both muscles, the normal arrangement is for the 

 muscular bellies to be limited to the proximal portion of the le^ 

 and to give rise to very long tendons. The Pigeons and Doves 

 show the type of the Chaiudriiform group, but also indications of 

 moving away fiom it. 



In the Alectoromorph group generally, the P. longus remains 

 as the dominant muscle and, except in the aberrant Finfoots, is 

 always large and powerful. The P. brevis varies, sometimes 

 being very feeble or absent, but in some of the Columbae, as an 

 exception, shows signs of outstripping the P. longus. The gi'eat 

 lengthening of the tendons of both muscles in some of the 

 Ralliform and most of the Charadriiform birds may easily be 

 regarded as in correlation with the long legs of these birds. It 

 is interesting to note that the Columbae show signs of a former 

 long-legged Charadriiform condition. 



CORACIOMORPH^. 

 CUCULIFORMES. 



C u c u 1 i . 



Cuculidfe. Caculus canot'us (2 examples). GvAra ^^i^'i^'igua 

 (2 examples). Hierococcyx varius. — In the Guira cuckoo the 

 P. longus is a large muscle with good superficial, fascial^ and 

 deep origins. Its tendon gives oft" a long narrow anchor and 

 then passes on to form the slip to III. In Hierococcyx the longus 

 is relatively smaller and the anchor is broader. In Cuculus the 

 deep origin is much the most important, and is. chiefly from the 

 distal end of the shaft. In all the P. brevis is well developed, 

 with a strong origin from the tibia below the fibula and a varying 

 extension up the fibula. The tendon of insertion I'uns the usual 

 course under the slip to III, and flattens out to an insertion 

 placed so that the muscle not only flexes the foot but has a con- 

 sidei'able power of rotation. 



Musophagidas. Corythaix pe7-sa (2 examples). Turaciis cory- 

 thaix. — The P. longus is a large muscle with extensive superficial 

 and fascial origins and a small deep origin extending down the 

 fibula,. The anchor is very broad, and the slip to III well marked. 

 The P. brevis is a long rounded muscle arising from about the 

 distal three-quarters of the length of the shaft, from the fibula 

 and tibia below the fibula. The tendon passes through a fibrous 

 bridge and then flattens out to the usual insertion. 



In the Cuculi the P. longus remains the dominant muscle, but 

 there are signs of its being reduced to a deep origin with corre- 

 sponding increase of the importance of the P. brevis. The group 

 shows, in fact, a transition from the condition which I regard 

 as more generalized towards the particular type of specialization 

 which becomes more and moi'e marked in other Coraciomorphines. 



