416 DU. p. CHALMERS MITCHELL ON THE 



after a very short common course ; tlie brevis tendon is very 

 broad and gives oft' a distinct distal slip (gamma of Fiirbringer), 

 a median patagial fan, and a separate proximal slip (alpha of 

 Fiirbringer). There is no I'ecm-rent anchor to the longus tendon. 

 The longus tendon is doubled at the elastic part and receives the 

 whole of the biceps patagial is, the tendon of which is very short. 

 The pectoralis patagialis is large and runs to the patagial tendon, 

 where it divides into longus and brevis slips. The condition in 

 RhinocheUis is as I have already figured {loc. cit. text-fig. 76), 

 except that the alpha and gamma divisions of the brevis were 

 rather better separated. 



Deltoides major et minor. — The major is a strong muscle reach- 

 ing down to the end of the third quarter of the humerus ; it is 

 shorter in Rhinochetus. The n^iinoi% as in other Gruiform birds, is 

 quite separate, and is inserted to the other side of the insertion 

 of the pectoralis minor. 



Pectoralis thoracicas. — A very strong muscle with a feeble 

 fibrous anchor to the humerus, and a single elongated tendinous 

 insertion. In Rhinochetus the miiscle is similar, except that it is 

 narrower, in association with the shallow keel of the sternvim. 



Supra- cor acoideus {^pectoralis minor), coraco-hrachialis extermis, 

 coraco-hrachialis iniernns, and suh-coraco-scapularis. — Practically 

 identical in their relations in the two species of Aramus and in 

 Rhinochetus, except that in Rhinochetus the coracoidal origin of 

 the last-named muscle is relatively verj^ much larger. 



Anconaeus. — The humeralis division, as in the vast majority of 

 birds, is a stix)ng muscle arising froiar the greater part of the 

 humerus, and is cleft proximally. The scapular head, in addition 

 to the stout anchor to the humerus described in connection with 

 the latissimus doi'si muscles, has the origin from the scapula 

 forked in Aramus, simple in Rhinochetus. The anconteus caput 

 coraeoideiim (expansor secundariorum) in Aramits presents the 

 arrangement described as " ciconine " by Garrod ; that is to say, 

 it arises in the axilla from a triangular ligament which passes 

 into a stout tendon running to be inserted to the proximal 

 secondary quills. I have already stated (P. Z.S. 1901, p. 645) 

 that this arrangement is usual in Gruiform birds, but that I 

 found the muscle feeble, although present, in Rhinochetus and 

 Eurypyga. In the example of Rhinochetus which I used in the 

 dissections I am now describing, I found no trace of the expansor 

 secundariorum in either of the wings. This may serve as 

 another of the many warnings against attaching systematic value 

 to the absence of an anatomical strvicture, as it may have been 

 lost independently by different descendants of a common 

 ancestor. 



Biceps hrachii. — In Aramus the acrocoracoidal portion of the 

 muscle gives rise to a tendon which, although closely associated 

 with the humeral poi'tion, can be traced separately to the ulna, 

 the humeral portion going to the radius. In Rhinochetiis the 

 division of the tendon of insertion to the radius and ulna is 



