1898.] OSTEOLOGY OP THE IMPENNES. 988 



b, Quadrato-jugal bar slightly curved. 



c'. Supra-orbital ledge nearly obsolete, not extending far beyond the base 

 of the postorbital process ; supra-orbital groove shallow, bounded 

 posteriorly by a bony ridge Etidyptes, 



B. Posterior region of the temporal fossa very deep, extending mesially on to 

 the cerebellar prominence, separated dorsally from its fellow of the 

 opposite side by a median sagittal ridge; transverse lambdoidal ridge 

 absorbed by the squamoso-parietal wings, which are largely developed ; 

 with a coronal ridge distad of the sagittal crest Spheniscvs. 



Key to the Species. 



Aptenodttes. 



a. Upper jaw slightly longer than the cranium (4 in.) ; squamoso-parietal wings 



almost obsolete ; coronoid of lower jaw long, extending far forwards above 

 middle of splenial, terminating near the middle of the jaw. A. forsteri. 



b. Upper jaw markedly longer than cranium, more than 3 ; squamoso-parietal 



wings extending nearly the whole height of the temporal fossa ; coronoid 

 short, not extending beyond the posterior ^ of the jaw ... A. patagonicus. 



PXGOSCELIS. 



a. Dorsal border of free edge of supra-orbital ledge of great breadth (PI. LIX. 

 fig. 2) ; posterior region of temporal fossa moderately deep : total length 

 of skull 6 in F. papua. 



h. Dorsal border of free edge of supra-orbital ledge about "1 to -2 in width ; 

 skull less than 5 in. long ; interorbital region of frontal immediately behind 

 nasals reduced to a slender ridge dividing the supra-orbital grooves. 

 a'. Upper jaw not greatly depressed, markedly lorgerthan cranium ; ptery- 

 goids longer than vomer ; length of anterior nares equals width across 

 skull behind the postorbital processes P. antarctica. 



b'. Upper jaw markedly depressed, equal to or less than cranium in length ; 

 pterygoids equal vomer in length ; length of anterior narial aperture much 

 less than width of skull behind postorbital processes. P. adelicB. 



Cataeehactbs. 



a. Inter-orbital region of frontals behind the nasals forming a broad ridge. 



a'. Size smaller, not exceeding 4-3 in | ^- '^hrysocorm 



[ (J. pacnyrhynchus. 



b'. Size larger, not exceeding 4-6 in C. chrysolophus. 



ElJDTPTIJLA. 



a. Skull 3-5 in.; transverse lambdoidal ridge equals length of narial aperture. 



E. minor. 



b. Skull 3-8 in.; transverse lambdoidal ridge less than length of narial aperture. 



E. albosignaia. 



Sphbniscus. 



a. Squamoso-parietal wings greatly developed, superiorly separated from the 



coronal ridge by a long and often wide sagittal ridge ; cerebellar dome not 

 well developed ; supra-orbital ledge sharply truncated anteriorly in the 

 region of the posterior ^ of the supra-orbital groove... S. demersus. 



b. Squamoso-parietal wings well developed, superiorly running forwards so as 



nearly to join the coronal ridge ; supra-orbital ledge obsolete. 



S. magellanicus. 



