386 STRUCTURE AND CLASSIFICATION OF BIRDS 



likely that the wings of this bird were more efficient than 

 those of the ratites on account of the apparently well- 

 developed remiges. 



COLYMBI 



Definition. Oil gland tufted. Afiershaft present. Aquiiicubital. 

 Accessory semitendinosus absent Biceps slip present. G-lutseus 

 maximus large, extending behind acetabulum. Caeca long. 

 Skull holorhinal, without basipterygoid processes, schlzogna- 

 thous. Tibial crest strongly developed. 



This group of birds contains two very well-marked families, 

 the divers (Colymbidse) andthe grebes (Podicipedidse). In view 

 of their numerous and important points of similarity I have 

 not thought it desirable to separate these two families quite 

 so widely as has GADOW. The Colymbidse contain but one 

 genus, Colymbus, with four species. Of the grebes there is 

 perhaps also only one well-marked genus, Podicipes. But 

 the Central American Centropelma (of SCLATEE and SALVIN) 

 has some claims, on account of the complete loss of flight, to 

 generic distinction, while in the course of the following pages 

 it will be seen that there are certain, if small, reasons for 

 distinguishing jEclimopliorux and Tac/iybaptes. Podilyinb/tx, 

 another alleged genus, has not been dissected. 



Our knowledge of the anatomy of this group of birds is 

 chiefly due to NiTZSCH, 1 BEANDT,* CoiiES, 3 SnrFELDT, 4 and 

 myself. 5 



As to external characters, there is a close agreement 

 among the Colymbi. The number of rectrices in Colymbtis 

 glacialis I find to be twenty. NITZSCH gives eighteen to 

 twenty for the genus. Specialised rectrices are not recognis- 

 able among the grebes. The inferior tract of feathers is 



1 Loc. cit. 



' l ' Beitriige z. Kenntniss d. Naturg. d. VSgel,' Mem. Ac. St. Peterxb. 1840, 

 p. 197. 



a ' On the Osteology of Colymbtt*,' Ac., Mi-m. Bost. Soc. Nat. Hist. i. 1866, 

 p. 131. 



4 ' Concerning the Taxonomy of the N. American Pygopodes,' Ac., J. Anat. 

 1' lii/ft. 1892, p. 198. 



5 ' Notes upon the Anatomy of a Grebe (JEchmoplwrus major),'' etc., P. Z. S. 

 1H%, p. 538. 



