jO-J6 on tuk osteology or the pygopodes. [Dec. 19. 



jrro. = prootic. so. I. = supraorbital ledge. 



yv;. = pterygoid. »</. — squamoBal. 



y. 3= quadrate. .>;9.p. = squamosal proiniuence. 



.>.-.<7. = supra-angular. .s^.yjM'.^^squamoso-parietiil wing. 



«.<•. = sagittal crest. ("./'. = temporal fossa. 



A-.o.=supraoccipital. r'»-.^. = trigeminal foramen. 



so.ff. = supraorbital groove. v. = vomer. 



Fig. 1. Dorsal aspect of the skull of Poclici2)(s cristatiis (p. 1()20), to show the 



well-developed sagittal crest, temporal i'ossa, coronal ridge, squamoso- 



parietal rings, the free lachrymal, and the feeble supraorbital grooves. 

 Fig. 2. Dorsal asjaect of the skull of Colymbus septentriovalis (p. 1020), to 



contrast with fig. 1, with the great development of the supraorbital 



grooves and ridges and the lachrymal foutauelle. 

 Fig. 3. Lateral aspect of fig. 2 (p. 1021), showing the conspicuous cerebellar 



prominence, temporal fossa, and supraorbital ledge. 

 Fig. 4. Lateral aspect of the skull of a nestling Podicipes cristatiis, outer view 



(p. 1030), to show the unclosed sutures. 

 Fig. 5. Lateral aspect of the skull of a nestling Podicipes cristatus, inner view, 



to show the unclosed sutures. 

 Fig. 6. Ventral view of skull of an adult Colymbus septentrionalis (p. 1026), to 



show the schizognathous palate. 

 Fig. 7. Lateral aspect of a portion of the pterygoid and palatine of Colymbus 



glacialis (p. 1032), to show the hemiptervgoid. 



