226 



OSTEOLOGY OF ANSERES. 



above its own posterolateral plane and the ischium which lies be- 

 low it. _ _ , 



In the present specimen this convexity shows a large fenestra in 

 either ilium al its anterior part. No such vacuity exists in the Eider 

 nor other Ducks in my possession. In some specimens the bone in the 

 same locality is so thin that I expect it occasionally occurs in those birds 



also. 



Fig. 7. Pelvis of Mergus serrator; viewed 

 from above. (Specimen 16626, Smithsonian 

 collection.) 



Fig. 8. Same view of pelvis of Somateria dreg- 

 seri. (Specimen 16980. Smithsonian collection.) 

 BotL ajmres life size. By the author. 



As already stated there are seven tree caudal vertebra and a py- 

 gOStyle. The neural canal passes through all of the former and a short 

 distance into the latter. Above it the neural spines are notched in 

 front, aud have an elevated, stumpy process behind. 



