ANATOMY OF GRUIFORM BIRDS. 419 



identical with the tendon of insertion of the semimembranosus 

 in Aramus and Rallus. This tendon arises from the semiten- 

 dinosus raphe, and the muscvdar bellies pass under it, meet a 

 separate muscle (text-fig. 3, Gc. 2) arising from the femur just 

 proximal to the accessory semitendin., and form a strong tendon 

 that joins the common tendon of the gastrocnemius. A glance 

 at text-figures 1, 2, and 3 will show that this muscle, marked Gc. 2, 

 appears to be present in Rcdlus, Armnus, Otis, and Rhinocheius, 

 but that in the two former it is fused along its edge with the 

 accessory semitendinosus, whilst in the two latter it is fi-ee. If, 

 then, we identify the muscle marked Gc. 2 in text-fig. 3 with tlie 

 middle head of the gastrocnemius, it seems a sufficient statement 

 of the facts to say that the middle head of the gastrocnemius in 

 Rallus is either absent, or fused with the accessory semiten- 

 dinosus. But in both species of Aravius, although the accessory 

 semitendinosus is sufficiently broad to pass both for itself and a 

 fused ralline-like middle head of the gastrocnemius, there is, in 

 addition, a distinct middle head (text-fig. 2,Gc. 2) apparently absent 

 in Rallies. In Fsophia, the middle head of the gastrocnemius is 

 double, one portion corresponding with the Gc. 2 in text-fig. 2, 

 another with the Gc. 2 in text-fig. 3. In my paper already cited 

 (P. Z. S. 1901) I stated that the external head of the gastro- 

 cnemius in Otis was trifid, one of the three origins passing under 

 the biceps. I do not doubt but that the latter is morphologically 

 identical with the slip marked Gc. 2 in text-fig. 2. In the example 

 of Rhinocheius that I am now describing, I found precisely the 

 same condition ; not only is the Gc. 2, represented in text-fig. 3, 

 present, but there is also a separate middle head corresponding 

 with the Gc. 2 of text-fig. 2. Dr. Beddard (P. Z. S. 1891, p. 16) 

 has published a description and an incompletely lettered figure 

 of the gastrocnemius and its relations in Rhinocheius. Although 

 his description is difficult to follow, as it omits reference to the 

 tibial head of the gastrocnemius which, so far as I know, occurs 

 in all birds, and refers to a head "formed by a broad flat tendon 

 to the head of the fibula,'' a disposition which is at lenst abnormal 

 in Avian anatomy, I infer that the arrangement of the gastro- 

 cnemius in the example of Rhinochettis that he dissected was 

 identical with that which I describe here. 



For some time I have been collecting notes on the various 

 fashions in which the middle head of the gastrocnemius and the 

 accessory semitendinosus aie disposed in birds, but I do not wish 

 to offer these results for pviblication until I can present a fairl}^ 

 complete picture of their distribution in the Avian system. Dr. 

 Gadow {Vogel, in Bronn'sThier-Reich, p. 184) distinguishes three 

 conditions of this complex: (i.) when the accessory semitendinosus 

 cannot be separated from the middle head of the gastrocnemius ; 

 (ii.) when both muscles are present but quite distinct except in so 

 far as they may be connected by secondary tendons ; (iii.) when 

 the accessory semitendinosus is absent but the middle head of 

 the gastrocnemius present. This grouping will not contain all the 

 facts ; there is a condition, as in Rhinochetics and Psophia, which 



