18 SHUFELDT — OSTEOLOGY OF THE CUCKOOS. LJan. 4, 



wise terminate in cartilaginous tips and curve up behind the skull 

 in the manner most usual among birds. 



There are about twelve osseous sclerotal platelets in the circlet 

 found in either eyeball. They present us with nothing worthy of 

 especial remark, seeming to possess their most usual ornithic char- 

 acters. 



It may be as well to add here a few words describing the ossifica- 

 tions of the trachea, and we find for the entire length of this sub- 

 cylindrical tube the osseous rings which compose it fail to meet in 

 the longitudinal median line posteriorly. 



The interval thus formed, which is not very great, is occupied by 

 a thin membrane which is continuous with the internal tympaniform 

 membrane of the lower larynx. As to shape, the trachea diminishes 

 in calibre gradually from above downward, and nowhere in its con- 

 tinuity does it present any enlargements or dilatations. 



This does not apply exactly to the bronchial bifurcations, for 

 each one of them shows a disposition to swell just before arriving at 

 the contracted parts of these tubes, where they impinge upon the 

 lung tissue. 



We may reckon either of these bifurcations as being partially 

 surrounded by thirteen semirings. Of course in this bird, as I say, 

 the entire trachea may be regarded as having only semirings, but 

 had the usual number of these united behind there would still have 

 remained the thirteen semirings to each bronchial tube. An osseous 

 pessulus is not present in Geococcyx, and the internal tympaniform 

 membrane is quite extensive. There does not even seem to be any 

 thickening of this membrane in our subject where this bony little 

 bridge is located in those birds where it exists. (For figures of the 

 trachea of Geococcyx see my memoir in the P. Z. S. cited above.) 

 Of the Remainder of the Axial Skeletofi — The Vertebral Column. — 

 This column presents us with eighteen movable vertebrae before we 

 arrive at the consolidated pelvic sacrum. This latter contains 

 eleven more segments, thoroughly united together and firmly joined 

 to the iliac bones. Finally, we find five vertebrae and a large 

 pygostyle in the skeleton of the tail of Geococcyx. 



In the cervical region we pass twelve vertebrae before we come to 

 the first one of the series that bears a pair of free ribs, the thirteenth 

 and fourteenth both possessing these appendages, and in both they 

 are well developed, though not reaching the sternum, through the 

 intervention of costal ribs. The pair on the fourteenth vertebra 



