AXIAL SKELETON OF THE STEUTHIOKID^. 49 



axis extremely long ; hypapophyses developed from eighteenth to twentieth vertebra ; 

 fossae beside preaxial part of dorsal neural spines very small ; sacro-caudal vertebrae 

 raised scarcely at all dorsad of acetabula ; postaxial part of ilium more convex ; inter- 

 obturator processes nearly meet, if not quite; ischium joining or not joining pubis; 

 ischium extends as far postaxiad as ilium ; pubis extends back as much as ilium ; 

 acetabula only so far ventrad of vertebral column that a minute portion of both can be 

 seen through when opposite ; ribs very wide, more straight than in Drommus ; uncinate 

 processes about three, but may be absent ; sternum very much longer than broad, no 

 median prominence to preaxial margin, obtuse median postaxial prominence, a very 

 deep median pit between coracoid-grooves, costal angles short, pleurosteon with four 

 or five costal articular surfaces. 



CHARACTERS COMMON TO APTERYX AND DINORNIS. 



Cervical vertebrae fifteen ; vertebrae with ribs nine ; hyperapophyses of axis large ; 

 neural spines of axis lofty ; hyperapophyses of axis moderate or extremely large ; cer- 

 vical vertebrae short ; neural spines of cervical vertebrae generally more or less well 

 developed ; catapophyses may form a ring ; diapophysial lamella extending towards 

 postzygapophysis, large and conspicuous, or extremely so; cervical ribs moderate or 

 small ; sacro-caudal vertebrae slightly raised dorsad of ventral margin of acetabulum ; 

 ischium and pubis uniting distally or not ; supratrochanteric process absent or incon- 

 spicuous ; postaxial part of ilium inclined somewhat ventrad ; interobturator processes 

 very slightly developed ; ischium and pubis diverging from ilium postaxially very greatly 

 ventrad ; ischium very broad, especially postaxiad ; pubis more or less slender ; acetabula 

 so far ventrad of vertebral column that their ventral halves, or more, can be seen through 

 when opposite ; fossa on each side of lumbo-sacral vertebrae conspicuous ; sternum 

 broader than long ; coracoid-grooves minute, very slightly marked and widely separated ; 

 no median process projecting from preaxial margin of sternum, costal angles moderate, 

 long median and lateral xiphoid processes. 



CHARACTERS OF APTERYX. 



Size much smaller than that of any other known genus of Struthionidae. Total 

 number of vertebrae from forty-five to forty-seven ; sacro-caudal vertebrae three ; preaxial 

 articular surface of atlas scarcely at all notched dorsally, hyperapophyses very long ; a 

 minute hypapophysis to atlas ; no hypapophysis to axis; neural spine of axis very high ; 

 hyperapophyses of axis extremely large ; cervical neural spines not bifurcating laterally ; 

 catapophyses commence at the fifth vertebra ; in the tenth and eleventh vertebrae they 

 form a ring ; hypapophyses developed from the twelfth cervical to the third dorsal 



VOL. X. — PART I. No. 7. — March, 1877. h 



