982 MH. W. p. PTCRAFT OS THE [Dec. 13, 



X. Key to the Osteology of the Impeitnes, 

 based on characters of the adult skeleton. 



A. Skull (Plates LIX.-LXI.) '. 



Beak never hooked ; nares pervious, holorhinal ; basipterygoid processes 

 absent ; palate schizoguathous ; vomer blade-sbaped, paired, the two halves 

 united along the antero-ventral border, never anchylosed with the palatines ; 

 palatines broad and flattened posteriorly ; pterygoids expanded into flattened 

 laniinsB distally, never rod-shaped ; interorbital septum perforate; with deep 

 supra-orbital grooves ; lachrymal free, never contributing to form the supra- 

 orbital grooves, and without conspicuous squamoso-parietal wings when the skull 

 is seen dorsally, its lower limb pedate, articulating with the quadrato-jugal bar ; 

 maxillo-palatine processes in the form of slender curved rods, never laminate. 



Key to the Genera. 



A. Posterior region of the temporal fossa not extending on to the cerebellar 

 prominence ; the squamoso-parietal wing bounding the fossa posteriorly, 

 terminating on the cerebral dome at or below the level of a long transverse 

 lambdoidal ridge ; coronal ridge absent. 

 a. Quadrato-jugal bar greatly curved. 



a'. Supra-orbital ledge feebly developed, decreasing in size from behind 



forwards and becoming obsolete at the level of the frontal end of the 



nasal bones ; supra-orbital grooves closed posteriorly by a strong 



bony wall ; posterior ends of nasal processes of premaxilla separate 



one from another and from the nasals throughout life. . . Aptenodytes. 



h'. Supra-orbital ledge greatly developed, with its free edge flattened 



dorsally. 



a" . Width of coronal ridge much exceeding the width across nasals 



between lachrymals ; squamoso-parietal wings feebly developed ; 



posterior region of temporal fossa shallow. 



a^. Nasal processes of the premaxilla slender, free posteriorly one 



from another and more or less easily distinguishable throughout 



from the superior limb of the na.sals ; inferior border of the 



squamosal prominence longer than that of the parcccipital 



process ; width of supra-orbital groove exceeding the height of 



the vertical axis of the foramen magnum ; lower jaw with the 



inferior limb of the posterior (caudad) end of the dentary with a 



straight superior border Fygo&celis. 



b^. Nasal proces.ses of the premaxiUa conspicuously thickened, fused 

 posteriorly more or less completely one with another and with 

 the superior limb of the nasal ; inferior border of the squamosal 

 prominence less than that of the paroccipital process ; width of 

 supra-orbital groove less than the vertical axis of the foramen 

 magnum ; lower jaw with inferior limb of posterior end of 

 dentary short and deep, and with a strongly pronounced sinuous 



free border Catarrhactes. 



b". Width of coronal ridge not exceeding width across nasals between 

 the lachrymals ; squamoso-parietal wings well developed ; posterior 

 region of temporal fossa wide and deep ; nasal processes of pre- 

 maxilla slender, free posteriorly one from another and from the 

 superior limb of the nasals ; inferior borders of squamosal pro- 

 minence and paroccipital process equal ; width of orbital groove less 

 than height of vertical axis of foramen magnum ; lower jaw having 

 the inferior limb of the posterior end of dentary produced far back- 

 wards, and with a strongly arched sujDcrior border... Mcgadyptes. 



^ Of the Keys appended, that of the skull expresses the systematic 

 arrangement adopted in this paper. The rest are designed not for systematic 

 work, but for the purpose of facilitating the identification of the different parts 

 of the skeleton when isolated. 



