PHYLOGENY OF THE PAL^OGNATHiE AND NEOGNATILE. 277 



b. Post-acetabular ilia closely approximated, the neural spines at most only 



barely visible between the closely approximated innominates ; no supra- 

 trochanteric process; ischia widely separated from post-acetabular ilium; 

 obturator foramen and fissure confluent ; post-sacral vertebrae of the 

 synsacrum welded into a large laterally compressed mass, bent down so 

 as to bring the neural crest to the level of the ventral border of the post- 

 ilium Apteryx. 



B. Pubes anchylosed caudad with one another or with ischium. 



c. Post-acetabular ilia widely separated from ischia, and from one another 



in the mid-dorsal line ; pubes fused caudad (a) with the ischia and (b) 

 with one another in the mid-ventral line ; the synsacral vertebrae appear- 

 ing below the level of the ventral border of the ilium Struthio. 



d. Post-acetabular ilia anchylosed with ischia, and with one another in the 



mid-dorsal line ; pubes anchylosed with ischia caudad ; ischia closely 

 united in the middle line one with another throughout almost entire 

 length (unique) ; the post-sacral vertebrae of the synsacrum atrophied . Rhea. 



Key to the Species. 



Rhea. 



a. Pre-ilium not projecting forward beyond the last thoracic vertebra and rib, 



which forms the limit of the synsacrum cephalad R. americana. 



b. Pre-ilium projecting forward conspicuously beyond the last thoracic vertebra 



and rib R. macrorhyncha. 



Apteryx. 

 A. Width across anti-trochanter equal to or less than the width of pre-acetabular 

 ilium at widest. 



a. Pre-acetabular ilium of great width, with a strongly arched dorsal border, 



and large laterally expanded antero-ventral angles ; width across pre- 

 acetabular ilia at widest part = to length of ischium, and far exceeding 

 length of post-acetabular ilium; post-acetabular ilium with a sudden 

 widening at its free end; breadth of pre-ilium at widest — breadth across 



anti-trochanter A. australis. 



]3. Width across anti-trochanter always greater than width of pre-acetabular 



ilium at widest; post-acetabular tapering caudad ; breadth of pre-ilium at 



widest less than breadth of anti-trochanter. 



b. Pectineal process large ; five lumbar vertebrae. 



a'. Post-acetabular ilium with a concave ventral border, and a slight notch 



immediately behind the anti-trochanter A. haasii. 



b'. Post-acetabular ilium with straight or convex ventral border ; no notch 



behind the anti-trochanter A. oweni. 



c. Pectoral process small ; four lumbar vertebrae A. a. mantelli. 



vol. xv. — part v. No. 22. — December, 1900. 2 q 



