No. 5.] SHUFELDT ON THE OSTEOLOGY OF EREMOPJIILA. 129 



ment. The median line on tlie dentary segment averages 5 centimetres, 

 this portion of the bone being quite thick and concave above, convex 

 below. The general surface, both inside and out, between the bounda- 

 ries just defined, is in each case depressed, smooth, and translucent until 

 we arrive at the solid dentary portion, where we find it marked by a 

 row of minute pits. Of some dozen or more lower maxillai before me, 

 one of the most striking differences existing among them seems to be 

 the variation in size of the interangular vacuity or foramen. This is 

 elliptical in outline with the major axis of the ellipse in the long axis of 

 the bone, and in some specimens squarely meet the raised ramal borders 

 within, while in other individuals, even though the bone be larger, this 

 foramen is markedly smaller. A large concavo-convex sesamoid is found 

 between the tympanic and articular end on each side. The long axes of 

 these bones are placed vertically, and their concave surfaces look for- 

 wards. They are attached to the middle of the i)ointed articular pro- 

 cesses behind by a delicate ligament, and above by the same means ; by 

 a somewhat broader attachment to the squamosals and tympanies, pos- 

 teriorly. 



Spinal column, cervical portion — (PI. IV, Figs. 22 and 35). — In making 

 a study of the vertebral column of this Lark, the student will find 

 that he will be materially assisted if he make use of an engraver's eye- 

 lens, or, better still, one of the low-power objectives of a good micro- 

 scope, as some of the points for examination are rather minute, and are 

 not to be so easily or satisfactorily demonstrated by the unarmed eye. 

 The cervical portion of the column is composed of thirteen vertebrae ; 

 these enjoy, from the atlantal throughout the entire series, a perfectly 

 free movement among each other by their several articular surfaces j and 

 some form of the sigmoidal curve, characteristic of the bird-neck, is in- 

 variably preserved during life and action. We find, too, the majority 

 of the salient points pertaining to these segments described by ornithol- 

 omists present and strongly marked, and the chief functions of this 

 jointed and bony isthmus well carried out — as aftbrding protection for 

 the myelon in its passage from the brain to the body below, and the 

 vessels from their centre to the brain above. The neural canal, begin- 

 ning in the atlas as a transverse ellipse, rapidly becomes circular, re- 

 taining this form throughout the tube, only to resume the elliptical again 

 in the last two or three segments, where in the thirteenth it seems to be 

 of a larger calibre than at the cranial extremity, the ellipse still being 

 placed transversely. 



The usual i)rocesses of ten of these vertebrse, the third to the twelfth, 

 inclusive, afford protection to the vertebral artery and sympathetic 

 nerve. By an api^areut contraction of the parapophyses in the twelfth, 

 the canal is open laterally in this segment. It is confined to the anterior 

 third on each side of the vertebrae enumerated, and is exceedingly small 

 throughout its extent ; its largest calibre being at its commencement, 

 its finest in the tenth or eleventh. Among the long vertebriB in the 

 9 GB 



