^4 BULLETIN UNITED STATES GEOLOGICAL SUEVEY. [Yol.Yl. 



fine ridge riinning across tliem transversely. Internally they are drawn 

 out gradually into subcylindrical processes tliat i)oint upwards, in- 

 wards, and a little forwards, exhibiting superiorly on each, about the 

 middle, an oval pneumatic foramen. The upper edge rises rather ab- 

 ruptly from the articular ends, x)resenting as it arrives near the general 

 level a rudimentary coronoid for the insertion of the tendon of the tem- 

 poral. With the exception of a little elevation where the dentary ele- 

 ment meets the surangular, the suj)erior outline is unbroken ; it falls 

 away rapidly as it approaches the symphysis, where, with the opposite 

 border, it completes a little notch at the extremity. The tomium is 

 not as sharp as in the upper bill, and the mandibles do not fit nicely to 

 each other until covered with their horny sheaths. The inferior border 

 is rounded throughout its extent, and on a level at its posterior com- 

 mencement with the under surfaces of the articular ends and running 

 nearly parallel with the superior. The curve described by the rami 

 Ijefore they meet at the symphysis inferiorly approaches the parabola in 

 •outline. The sides of the jaw are nearly smooth internally and exter- 

 nally. The vacuity that occurs in so many birds at the junction of the 

 middle and inner thirds is rather large, long, and spindle-shaped, and 

 filled in, in tlie fresh state, by an attenuated membrane. 



The spinal column ; cervical 2'>ortion.— There are fourteen cervical ver- 

 tebrae, each one having a more or less free movement with the one be- 

 yond and behind it, maintaining in all positions some variation of the 

 usual sigmoid curve observable in the division of the vertebral column 

 throughout the class. The arrangement, as well as the direction, of 

 the planes of the zygapophysial articular surfaces allow considerable 

 Totary movement in the vertical plane, with combinations of the two. 

 It is a common habit of this bird, among other of his antics, to duck 

 Ms head smartly downwards and again upwards, several times in suc- 

 -cession, upon being approached. The relative position of the cervicals 

 has been figured in Plate I from the dead bird, placed in the act of 

 this particular manoeuvre, in a specimen after careful dissection. The 

 calibre, as well as shape, of the neural canal in this portion of the spinal 

 •column varies at different points. It originates at the atlas as a trans- 

 verse ellipse, with a major axis of four millimetres and a minor axis of 

 a little less than three millimetres ; this is about the maximum capacity 

 throughout the entire canal. From the atlas to the sixth or seventh 

 vertebra the ellipse gradually approaches the circle, with a marked di- 

 minution in size, its diameters being at the seventh about two milli- 

 metres in any direction. From this point to the twelfth, inclusive, it 

 rises as it fell, from the atlas, and in the same manner, when we again 

 discover a transverse ellipse, perhaps a jot smaller than the one de- 

 scribed in speaking of the atlas. In the thirteenth the canal is smaller 

 than, though in all other respects resembles, the twelfth, but an' abrupt 

 change takes place in shajje as we pass to the fourteenth or last cervi- 

 cal, where the form of the neural tube suddenly approximates the cir- 



