160 DR. P. CHALMERS MITCHELL ON THE [May 16, 



at their insertions. Any well-marked deviation from this condition 

 may be regarded as derivative. I have shown that in the more 

 specialised Columbidpe the posterior division of the muscle tends 

 to disappeai- (4) ; in the Kingfishei'S the anterior division similarly 

 is in progressive diminution (5) ; in most of the Gruiform birds 

 the anterior division is less sti'ongly marked, whilst the postei'ior 

 division tends to increase greatly in size and strength, whilst in 

 the Crane and Bustard it is the posterior division which dis- 

 appears (7). In the Limicoline birds generally the anterior 

 division i-emains in the primitive condition, whilst the posterior 

 tends to enlarge as it does in the Rails, the enlargement being 

 specially a backward and downward extension of the origin. On 

 the other hand, in the Woodcock, as an exception, there is a 

 disappearance of the posterior division. 



Latissimus dorsi meta-patagialis. — This muscle is probably 

 present in all these birds, but it is very slightly developed and apt 

 to be removed in the process of skinning. 



Rhomhoideus siqjerficialis et profundus. — Of these two muscles, 

 the supei'ficial is phylogenetically older. In all these birds it is 

 the thinner of the two muscles, but is longer, being longest in 

 (Edicnemus and Chionis, whilst it shows a general tendency to die 

 away posteriorly. In Chionis it is nearly divided into a proximal 

 and distal portion by a thin centi-al ai'ea, a secondary cleavage which 

 is well marked in the deep muscle of the eutaxic Kingfishers. 



The deep muscle in Hydrojihaskmus is almost of the same length 

 as the superficial muscle and it is difficult to separate the two. In 

 the others it is well separated by its greater thickness and by the 

 slope of its fibi-es upwards and forwards from the scapula to the 

 vertebrse. Its origin begins at the extreme posterior end of the 

 scapula and extends foi-wards under the origin of the sviperficial 

 muscle, but never reaching so far forwaixls. 



In the condition of these muscles, then, the Limicolpe are fairly 

 homogeneous ; the older superficial muscle is well developed, 

 extending in front of the deep muscle, but, except in Scolopax, 

 leaving a portion of it exposed behind. The deep muscle has made 

 comparatively little pi-ogress in foi-ward extension along the line 

 of the scapula and clavicle. 



Bice2)s hrachkdis. — This muscle displays in (Edicnemus the 

 condition normal in the majoiity of birds ; it arises by a narrow 

 tendon from the acrocoracoid, and by a broad tendon from the 

 proximal end of the humerus ; the rounded belly runs down the 

 arm and ends in a forked tendon, the thicker fork being inserted 

 to the radius, the thinner to the ulna. No doubt, fleshy origins 

 must have preceded tendinous origins, and there is considerable 

 variation as to the relative size of the two origins and insertions in 

 difierent birds ; but the (Edicnemus condition is a fairly central one, 

 and it is interesting to notice that in this respect (Edicnemus stands 

 apart from other Limicoline birds and might be associated with many 

 other groups. In Hydrophasianus there is a comparatively slight 

 deviation from the noi-mal, consisting in the complete disappeaiance 



