268 MR. W. P. PYCKAFT ON THE MORPHOLOGY AND 



posteriorly by its mesial border with external border of the combined vomer 

 and pterygoid ; vomer of great length, continued forwards beyond the 

 free end of the parasphenoidal rostrum; pterygoid laminate; orbital 

 process of quadrate decurved and articulating with the pterygoid at its 

 base ; anterior palatine foramen very small, and lying near the tip of the 

 beak beyond the vomer ; anterior narial and lachrymo-nasal fossae, in 

 dried skull, confluent ; mesethmoid with a truncated anterior border ; 

 nasal process of premaxilla rod-shaped ; nasal with a vestigial external 

 process. 

 a!. Vomer expanded into a broad flattened plate between the maxillo- 

 palatines, and separated from the parasphenoidal rostrum; beak 

 dorso-ventrally depressed ; palatine fenestrated posteriorly, not anchy- 

 losed with pterygoid; horizontal plate of mesethmoid appearing on 

 the surface of the skull between nasals, but never inflated to form a 

 casque; lachrymals fusing with nasals and frontals ; with long supra- 

 orbital processes Drom&us. 



V . Vomer only very slightly expanded between the maxillo-palatines ; beak 

 laterally compressed; palatine unfenestrated and anchylosed with the 

 pterygoid and vomer; horizontal plate of mesethmoid, nasals, and 

 more or less of frontals inflated to form a casque, sometimes of great 

 size ; quadrato-jugal fossa not extending forwards to level of antorbital 



plate Casuarius. 



b. Vomer large, trough-shaped, closely investing the parasphenoidal rostrum ; 



distal end of pterygoid and hinder end of vomer hidden (in ventral aspect 



of skull) by the palatine which underlies them ; pterygoid rod-shaped. 



c'. Vomer deeply cleft anteriorly, exposing the parasphenoidal rostrum 



between a pair of long spurs ; anterior palatine foramen long and 



slit-like. 



a". Lachrymo-nasal fossa bounded anteriorly by a bony spike rising 



upwards from the middle of the external border of maxillo-palatine ; 



with large post-orbital processes ; orbital process of quadrate very 



short, not extending beyond level of articulation with pterygoid ; 



lachrymal with large orbital processes ; mesethmoid visible as a 



lozenge-shaped plate between nasals Rhea. 



b" . Lachrymo-nasal fossa bounded anteriorly by a delicate rod articu- 

 lating above with the nasal and below with the hinder border of the 

 maxillo-palatine plate ; no post-orbital processes ; orbital process of 

 quadrate moderately long, with a free end projecting beyond articu- 

 lation with pterygoid ; lachrymal without orbital processes ; nasal 

 schizorhinal; inter-orbital septum perforate; mesethmoid not visible 



on surface of skull Tinamidce. 



d 1 . Vomer truncated anteriorly, not extending so far forward as the end of 

 the parasphenoidal rostrum; anterior palatine foramen small, closed 

 by anterior end of parasphenoidal rostrum ; large post-orbital processes ; 

 lachrymals fused with frontals and not readily traceable; orbital 



