1042 MR. W. p. PiX'RAPT ON THE [DeC. 19, 



families ; Dr. Gadow would regard these as of subordinal A'alue. 

 Which of the two views will become ultimately adopted remains to 

 be seen. Probably the first is a sufficiently wide separation. 



Finally, — and it had almost escaped mention, — the skeleton of 

 the Pygopodes is non-pneumatic. 



xi. Key to the Osteology op the Pygopodes. 



A. Skull. (Plate LXXII.) 



Holorhinal and schizognathoiis ; nares pervious ; Tomer cleft posteriorly ; 

 basipterygoid processes absent ; lachrymal small, feebly developed, not extending 

 downwards to join the quadrato-jugal bar; quadrate with an elongate orbital 

 process ; maxillo-palatine processes in the form of horizontal laminse, never 

 extending as far backwards as the scroll-like antero-internal border of the 

 palatine ; basitemporal plate of the parasphenoid with an inflated anterior 

 border converting the Eustachian grooves into tubes, with a median aperture 

 below the parasphenoidal rostrum ; temporal fossa; more or less well developed. 

 Dentary suture of mandible tending to disappear in the adult. Angulare 

 truncated. 



A. Supraorbital grooves very deep, with a well-developed ledge ; temporal 



fossffii wide, separated one from another superiorly by a median sagittal 

 ridge ; lachrymal more or less corapletelj' fused with the nasal ; vomer 

 grooved and laterally expanded dorsally ; with a deep median, ventral 

 keel, and with a strongly marked ventral keel in IVont of the parasphenoidal 

 rostrum ; Eustachian grooves never completely closed ; large postorbital 



and paroccipital processes Colymbidjs. 



(Only one genus — Coly^nbus.) 



B. Supraorbital grooves feebly developed or absent ; lachrymal free, not 



projecting posteriorly from the sides of the supraorbital margin ; vomer 

 i)lade-shaped ; Eustachian grooves completely closed ; postorbital and 

 paroccipital processes obsolete Podicipedid.e. 



Key to the Genera of the Family Podicipedidte\ 

 A. Without a broad bifid, overhanging postorbital process. 



Group a. (Type P. cristatus.) With a wide and distinct temporal fossa, 

 and strongly marked cerebral prominence ; postorbital region of the 

 frontal marked by a deep scar, for the temporalis muscle, the superior 

 border of which has a rough edge; upper jaw longer than cranium. 



^ I do not feel justified in attempting to form " Keys" to the species, either 

 for the skull or any other part of the skeleton, of the forms comprising the two 

 sub-families dealt with in this paper. Inasmuch as of the Golymbidse I have 

 only two species, C.glacialis and C. septentrionalis, and these are easily recogniz- 

 able by the difference in size alone. In the Podicipedidse I have only 8 out of 

 a possible 19 species of the genus Podiclpes ; onl3r one skeleton of Mchmophorus, 

 and no bones whatever of Podylimhus. From what I can gather from our 

 material, the difference between the three genera recognized in the British 

 Museum Catalogue vol. xsvi. is very slight, and that between the species 

 comprising these genera is even less. The genus Fodicipes seems to divide 

 itself into two groups — one of the type of P. fluviatilis, and one of the type of 

 P. cristatus. The differences upon which such separation rests concern the 

 skull only, and depend mainly upon size ; the smaller species having a 

 relatively shorter and wider skull, and ill-defined temporal fossie. 



