Page 200. 
330 ON THE ANATOMY OF CHAUNA DERBIANA. 
In conclusion, it seems to me that from considerations of ptery- 
losis, visceral anatomy, myology, and osteology, the Screamers cannot 
be placed along with the Anserine birds. In the windpipe and the 
form of the angle of the jaw they, no doubt, closely approach them, 
In their alimentary canal they are much nearer to Struthio and Rhea 
(not Dromeus and Casuarius) than to any other birds. There is a 
Ciconine tendency in their myology, whilst their osteology points in 
no special direction. It seems, therefore, to me that, summing these 
results, the Screamers must have sprung from the primary avian stock 
as an independent offshoot at much the same time as did most of the 
other important families. It may be fairly asked what reason there is 
for the assumption that there was a sudden break up of the bird-type 
at any particular period. It appears to me from the study of anatomy 
that this was the case; and it is evident that the acquisition of wings 
by the previously terrestrial type form must have suddenly inter- 
polated a large number of intruders into domains already occupied, 
and must have all at once called forth a new aerial struggle for exist- 
ence, which, from the generalness of its action must, within a short 
time, have brought out a great number of special characters by natural 
selection. 
EXPLANATION OF THE PLATES. 
Purate 14 (XII.) 
Fig. 1. Proventriculus and gizzard of Chauna derbiana, cut open, and part of the 
front wall removed. 
. Anterior view of lower portion of windpipe of C. derbiana. 
. Back view of same, the muscles of the left side haying been removed. 
. Right side view of same. 
. Portion of right coracoid bone (c) with coraco-brachialis longus (c.b.c.) and 
coraco-brachialis brevis (c.b.b.) in situ of Crax globicera. The expansor 
secundariorum (e.s.) is seen to spring partly from the first-named muscle. 
Puate 15 (XIII). 
Fig. 1. Ceca of Chauna derbiana, with the anterior wall partly removed to show 
the cavity intervening between the small and large intestine into which 
the czeca open. 
2. The cxca, external view. 
Prate 16 (XIV). 
Fig. 1. Axillary muscles of right side of Chawna derbiana. e.s, expansor secun- 
dariorum ; p 1, great pectoral ; p 2, second pectoral ; ¢.b./, coraco-brachialis 
longus ; 8, biceps; #, triceps; ¢.p.b, tensor patagii brevis ; sc, scapula; st, 
sternum; ¢, coracoid; jf, furcula; %, humerus; ¢.v, cervical vertebre ; 
ir, trachea: pat., patagium; S.R, secondary remiges. 
2. The same part, left side, of Gallinula chloropus. B. slip, biceps slip; ¢.p. 
tensor patagii longus. 
oe Ww bd 
