1901.] aosATOMY OF OKll roRM BIRDS. 643 



anatomically most simple ; the whole muscle is fleshy and short 

 and is inserted directly to tin- longtts tendon rather high up. In 

 Psophia the origin and insertion to the longus are also fleshy, but 

 the whole slip is much longer, so that the insertion is more distalh 

 placed, on the elastic portion of the tendon. In the others the slip 

 terminates in a tendon which fuses with the longus tendon after a 

 short separate course in Aramus, and after a very loug course parallel 

 with the longus in the Ballidae (text-fig. 77, p. 640) and in Heliomis 

 (text-fig. 78, p. 640). The Rails, except Porzana and Heliomis, show 

 an additional peculiarity. The tendon of the biceps propatagialis 

 forks, the outer fork runniug to 1 he longus as I have described, while 

 the inner fork spreads out on the patagial membrane, as the whole 

 biceps slip does in Pterocles (Fiirbringer). Beddard (1 ) figured the 

 arrangement in Heliomis differently ; bnl after a careful comparison 

 of his sketch with several dissections, I am satisfied that the tendon 

 marked x in bis figure is in reality the junction with the longus 

 displaced in dissectiou, while the other tendon in the specimens 

 1 examined ended on the patagium (as Beddard stated to be the case 

 in Pudica), and did not end on the brevi-. 



1 have not yet sufficient information to place these variations of 

 the biceps slip in order of apocentricity and archecentricity. It 

 appears to me to be probable that the biceps slip was originally a 

 cutaneous slip, and that a condition in which it spread out on the 

 patagium without definite connection with the longus and brevis 

 tendons is archecentric. Were this established, the condition 

 described by Beddard for Poclica, a eutaxic form, would be arche- 

 centric, while Heliomis and the Ballidae would stand next to it — 

 there being thus no correlation whatever between the condition 

 of this muscle and the condition of the feathering in the wing. 

 I may point out, also, that on this hypothesis the curious resem- 

 blance between the arrangements in Heliomis and the Rallidas, at 

 first sight so suggestive of affinity, could not bear such an inter- 

 pretation, as the common possession of an archecentric character 

 does not afford a direct clue. 



Deltoides major et minor. — In all 1 lie Grruiformes both these 

 muscles are present and the minor presents no variations of 

 importance. The major is a progressive muscle in most groups of 

 birds, its insertion gradually creeping down the humerus, a relatively 

 long extension being apocentric, a relatively short archecentric. 

 Of the Gruiformes the Grains display it in the most archecentric 

 condition, the extension of its insertion uot amounting to more 

 than the proximal third of the humerus ; in the Otididse, also ;i 

 Jiastataxic group, the insertion extends over the proximal half of 

 Ihe humerus. In Rhinochetvs, a eutaxic form, it is also relatively 

 short (text-fig. 70, 1). ), but its length is interfered with by 1 hecurious 

 accessory biceps. Among the Gruiformes it reaches its maximum 

 length in eutaxic forms such as /'.sujihia, where it extends over 

 six-sevenths of the humerus, and in the Dicholophide, where one 

 portion extends to about the end of the third quarter of the 

 humerus, but another portion, separated from the first by the 

 nerve running to supply the forearm, reaches the distal extremity 



