188 



they only got driven so closely together after their specific differentiation, 

 when the land gradually subsided, owing to volcanic action. The differentiation 

 of the family is as follows : — 



Skull with a short and wide beak. Pectoral girdle very small or absent, 

 wing absent, only an indication in Dinornis dromioides. Hallux absent or 

 present. An extension bridge to the tibio-tarsus, which is placed near the 

 inner border of the bone. No superior notch to the sternum. Most of the 

 species of very large size. The tarso-metatarsus is either long and slender 

 or short and wide, and its anterior surface may or may not be grooved. The 

 second trochlea is longer than the fourth, the third is not pedunculated, and there 

 is no perforation in the groove between the third and fourth trochlea. In the 

 tibio-tarsus the cnemial crest rises well above the head ; the extensor groove 

 is separated by a considerable interval from the inner border of the bone. 

 There is a well-defined intercondylar tubercle ; the intercondylar gorge is 

 deep, and there is no deep pit on the lateral surface of the entocondyle. The 

 femur may be either slender or stout, but is not markedly curved forwards. 

 The popliteal depression is deep, and the summit of the great trochanter 

 rises considerably above the level of the head. The pelvis approximates to 

 that of the Apterygidae, but the pectineal process of the pubis is less developed, 

 and the ischium and pubis may be longer and more slender. The coracoid 

 and scapula are aborted and may be absent. The sternum, which may be 

 either long and narrow, or broad and short, differs from that of the 

 Apterygidae by the absence of the superior notch, the divergent lateral 

 processes, and the reduction of the coracoidal grooves to small facets or 

 their total disappearance. The cervical vertebrae are relatively short, an 

 expanded neural platform as far as the sixth. 



In Anomalopteryx and Megalapteryx the number of cervicle vertebrae 

 is 21, and there are 2 cervico- dorsal and 4 free dorsal vertebrae, so it is fair 

 to assume that this is the correct number throughout the family. 



The feathers had after-shafts. 



DINORNITHIDAE. 



THE GENERA ARE AS FOLLOWS : 



Dinornis Owen. 



Megalapteryx Haast. 



Palapteryx Owen, part, 

 Palapteryx Hutton. 

 Tylapteryx Hutton. 



Anomalopteryx Lydekker, part. 

 •Mesopteryx Hutton. 



