OSTEOLOGY OF BIRDS 



257 



Both in form and position (or articulation) the palatines and 

 pterygoids of the Hooded merganser ( Lophod v t e s cucul- 

 1 a t u s ) apparently agree with M . serrator. 



The basitemporal region is broad and smooth, and a spinelike 

 process at its apex fails to shut out from view the double orifice 

 leading to the Eustachian tubes. 



We find the major portion of the crota- 

 phyte fossa upon the lateral aspect of the 

 skull. Still it may be seen also from a pos- 

 terior view, where the two depressions ap- 

 proach each other, but are separated by a 

 large domelike, supraoccipital prominence. 



This latter is usually pierced by an irregu- 

 lar foramen on either side, which is quite 

 characteristic but not always present in the 

 ducks and geese, and are small even in Loph- 

 odytes. In a specimen of Branta cana- 

 densis hutehinsii before me a large 

 cue occurs only on the left side of the promi- 

 nence. 



Mergus has a large foramen magnum which 

 faces almost directly backward. The occipital 

 condyle at its lower margin is of a reniform 

 outline with the notch above. 



In the mandible the symphysis is short, and 

 this bone, when seen from a superior aspect, 

 is of an acute Y-shape form. 



The anterior two thirds of either ramus is 

 narrow, tapering somewhat to the front, with 

 both upper and lower borders rounded. On 

 the outer surface a deep, median, and longi- 

 tudinal groove of hairlike proportion is drawn 

 along its entire length. 



The hinder third is much wider, nearly 

 double the width, and, instead of being thick 

 like the forepart of the bone, is a vertical 

 lamelliform plate. Its border is sharp above, 

 while below it is rounded, being in the same 

 line with the inferior border of the anterior 

 two thirds. 



The ramal fenestra is nearly or quite closed in by the surround- 

 ing elements ; a long, oblique slit marks its site. A curved projec- 



Fio. 2 Skull of Mergus 

 serrator; viewed from 

 above, mandible removed; 

 natural size. Drawn by the 

 author; same specimen as 

 shown in figure 1 



