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 Columbide the posterior division of the muscle tends 
to disappear (4); in the Kingfishers the anterior division sunilarly 
is in progressive diminution (5); in most of the Gruiform birds 
the anterior division is less strongly marked, whilst the posterior 
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 remains 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 imetapatagialis. —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. 
Rhomboideus superficialis et profundus— OF these two muscles, 
the superficial is phylogenetically older. In all these birds it is 
the thinner of the two muscles, but is longer, being longest in 
Udienemus 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 central area, a secondary cleavage which 
is well marked in the deep muscle of the eutaxic Kingfishers. 
The deep muscle in Hydrophasianus 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 fibres upwards and for wards from the scapula to the 
vertebre. Its origin begins at the extreme posterior end of the 
scapula and extends forwards under the origin of the superficial 
muscle, but never reaching so far forwards. 
In the condition of these muscles, then, the Limicolz are fairly 
homogeneous; the older superficial muscle is well developed, 
extending in front of the deep muscle, but, except in Scolopaw, 
leaving a portion of it exposed behind. The deep muscle has made 
comparatively little progress in forward extension along the line 
of the scapula and clavicle. 
Biceps brachialis——This muscle displays in Wdienemus the 
condition normal in the majority 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 
different birds; but the @dicnemus condition is a fairly central one, 
and it is interesting to notice that in this respect @dicenemus stands 
apart from other Limicoline birdsand might be associated with many 
other groups. In Hydrophasianus there is a comparatively slight 
deviation from the normal, consisting in the complete disappearance 
