PHYLOGENY OF THE PAL.^OGNATH.E AND NEOGNATH^. 171 



B. Nestlings. 

 The neossoptiles consist of prepennse only. 



In Dromceus, Casuarius, and Apteryx the prepenua has a well-marked rhachis and numerous 

 rami. The aftershaft is feeble or wanting. 



In Dromeeus the rhachis bears about 8 pairs of rami : the rami are produced into 



points beyond the distal radii. 

 In Casuarius the rhachis does not bear more than 5 pairs of radii. 

 In Apteryx the rami exceed 8 pairs ; the rami are not produced beyond the radii ; 

 the prepennse of some parts recall the adult down of Ducks. 

 In Rhea and Struthio the prepenua is umbelliform ; the main sliaft is represented by 3 rami, 

 the aftershaft by numerous rami. 

 In Tihea the rami of the main shaft are not greatly elongated or flattened. 

 In StrutMo the distal ends of the rami of the main shaft are much elongated and 

 peculiarly flattened and grooved, as in Tinamidce. 

 In Crypturi the prepenna is very complex ; the aftershaft equals the main shaft in length. 



OSTEOLOGY. 



The Skull of the Adult. 



The skull of the Palmognatluv — which, as we have elsewhere shown, includes the 

 so-called Ratitce and Tinamous — differs from all other known birds in that, in the adult, 

 the pterygo-palatine connection is by symphysis or anchylosis, and not by an arthrosis. 



The sknll of the Tinamous, as will be shown presently, closely resembles that of 

 Bliea. 



The Occipital Region (PL XLII. fig. 7). — The occipital condyle is sessile, and the 

 plane of the occipital foramen is inclined backwards, in all the Paloeognathce save 

 Dinornis, yUpyornis, and Aptergx, and in the Tinamous. In Dinornis the plane of the 

 occipital foramen is nearly vertical ; in Apteryx the occipital condyle is pedunculated. 

 In Dinornis and ^pyornis this condyle projects beyond the dorsal margin of the 

 foramen. In Dromeeus and Apteryx the supra-occipital, immediately above the foramen 

 magnum, presents the concavo-convex " cerebellar dome " so characteristic of the 

 Tuhinares and Sphenisci. There is a well-marked snpra-foraminal ridge (PL XLII. 

 fig. 8) running laterad on either side to become lost on the paroccipital process in all 

 save Apteryx and the Tinamous. In Apteryx the ridge ends abruptly in the form of 

 two pendent tubercles on either side of the foramen at about halfway down. In the 

 Tinamous the ridge terminates in the same region, but is without tubercles. The 

 occipital crest is most strongly marked in Rhea. The lambdoidal ridge nins outwards 

 and downwards as a sharply-defined ridge, terminating in a pair of strongly compressed 

 paroccipital processes, in all save Dinoriuscind Struthio. In these the ridge has a more 

 or less sinuous outline, and is not so easily followed. Only in Dinornis does the 

 lambdoidal ridge delaminate, as it were, in the region above the occipital crest, to 

 form anterior and posterior lambdoidal ridges. 



