No. 2.] SHUFELDT ON NORTH AMERICAN TETRAONID^. 333 



the same general appearance, differing principally in the length of their 

 outstanding transverse processes. In this respect the first and second 

 are about equal; in the third and fourth two or three millimetres are 

 added on either side, with a roughened tuberosity above ; while the fifth 

 and last is in appearance and size very much like the first. These dia- 

 pophyses are rounded at their extremities, and all slightly deflected. 

 The centra are transversely elliptical and of good size. The neura- 

 pophyses arise from them to inclose a subcircular neural canal, which is 

 roofed over by the bifid and clubbed terminations of the elements, that 

 hook or lean forward (Plate IX, Fig. 66; Plate XIII, Fig. 91). We 

 have never observed an hypapophysis upon any of them ; and all the 

 elements and processes, as always occurs in the coccygeal series, are 

 more or less imperfectly developed. 



The pygostyU is an acute subcompressed triangle with tuberous base. 

 Anteriorly and above it exhibits a bifurcated iDrocess that simulates the 

 crests of the series ; below this a shallow facet, for articulation with the 

 last caudal, and a feeble subconical depression to protect the termina- 

 tion of the my el on between the two. Behind it has, at its lower angle, 

 a deep groove, with a heavy bony rim or margin that shows a constric- 

 tion near its middle (Plate IX, Fig. 65). This formation is easily ex- 

 plained when we come to examine the development of this compound 

 appendage in the chick of a day or so old. This will reveal the fact 

 that the pygostyle is composed of three vertebrae, that are fused to- 

 gether, distorted and modified as the bird grows, so as to eventually 

 result in the bone we have before us. 



There is nothing more interesting to the student of comparative anat- 

 omy than to study the serial skeletons of birds of divers ages, demon- 

 strating and elucidating such a ijoint as this, that could not be brought 

 to light in any other way. 



We will now offer a few remarks upon- the vertebral column, as ap- 

 plied to others of the North American Tetraonidw. 



Of all the specimens examined, representing all the genera, the num- 

 ber of distinctly free vertebrae between the skull and the anchylosed dor- 

 sals has been found to be invariably fifteen, the last one supi^orting 

 movably-articulated pleurapophyses, that in Lagopiis, at least, possess 

 small cpi-pleural appendages. This portion of the spinal column, then, 

 will constitute the cervical division, and in it we note that the third 

 and fourth segments have interzygopophysial bars present, becoming 

 so broad in the quails that the foramina they give rise to are sometimes 

 very minute. 



The pleurapophyses become long and sharp in some and more con- 

 spicuous than in others; this applies particularly to Cnpidonia and Pe- 

 dioecetes. The last cervical in the former has osseous spicuhB leading 

 backwards from its neural spine and postzygapoi)hyses, as in the anterior 

 dorsals. In the same vertebra} the hj-papophyses become confluent to 



