682 DK. p. CHALMERS MITCHELL ON THE 



semitendinosus and semimembranosus, the condition Avhich I 

 found in Bcdf^niceps seems to be tj^pieal in Herons and Storks 

 (text-fig. 130). The middle head of the gastrocnemius is joined 

 by the semitendinosus just after the latter has been met by 

 its accessory. The accessor}^ oi-igin from the femur is parallel 

 to but separate from that of the middle head. The accessory is 

 present in Herons, Storks, Scopus, and in Ucdceniceps ; it is 

 frequently absent among the Steganopods. In my opinion the 

 middle head of the gastrocnemius is a sejoarated portion of the 

 accessory semitendinosus, and separation of the two, with sub- 

 sequent disappearance of oiie or of both, is a secondary or 

 specialized condition. 



Ilio-fibularis (Biceps). — Very strong fleshy origin from the 

 whole of the post-acetabular ridge of the ilium to the beginning 

 of the origin of the semitendinosus. The strong belly converges 

 to a rounded tendon which is inserted to the fibula after pa,ssing 

 through a sling in the usual way (text-fig. 129, BIC). The short 

 arm of the sling has a strong anchor to the fibula, which I happen 

 to have noted in Herons, but which is present also in manj' biixls 

 belonging to widely separated groups. 



Ischio-femoralis (Obdurator exteroius). — Arises by strong tendon 

 from external condyle of the femur (text-fig. 129, Ob.ex.) and 

 inserted fleshy to surface of the ischium. 



Obdurator (Obdiorator internus). — Origin by a strong tendon 

 surrounded by a gemellus muscle (text-fig. 129, OB. in. Gem.) from 

 the external condyle of the femur proximal to the obdurator 

 externus. Garrod (18) believed that in most cases the insertion 

 of this muscle to the inner aspect of the pubis and ischium 

 could be distinguished as oval or triangular, and attached some 

 systematic value to the condition. He described it as oval in 

 Steganopods and Storks and triangular in Herons ; in Bcdceniceps 

 it is plainly oval. 



P'ub-ischio-femorcdes {Adductor longus iiwdAdd. magnus). — The 

 external or longus is only about half the width of the inner 

 or magnus, but their origins and insertions are practically co- 

 extensive. In ni}'' notes I find that they Avere nearly equal in 

 Herons and Storks, but I have not paid special attention to the 

 point. The slips from the magnus to the tibia (text-fig. 130, SI.) 

 and the slip to the semimembi'anosus (text-fig. 130) I have not 

 noted in Storks or Herons. 



Peroneus superjicicdis (longus). — Strong muscle from crest of 

 tibia and fascia over the tibialis a,nticus ; usual insertion by broad 

 tendon to the fascia of the ankle and a long tendon running down 

 to join with the tendon of the perforated flexor of the third toe. 

 Precisely the same relations exist in Storks and Herons, but als'o 

 in so many other bii'ds that no systematic importance can be 

 attached to them. 



Peroneus jjrofundus. — A short but stout muscle from the tibia 

 below the fibula; its tendon passes over the ankle-joint to be 

 inserted to a knob on the outer side of the tarsus-metatarsus. 



