No. 2.] SHUFELDT ON NORTH AMERICAN TETRAONID^. 327 



Pneumatic foramina arc found about the bases of the transverse pro- 

 cesses, the most anterior one being of some size. 



The centra of these amalgamated vertebras are very much compressed 

 from side to side. This compression has its due influence upon the form 

 of the neural tube within, while the bone below is produced downwards 

 into an excessively thin and sharp crest, which is still further extended 

 into four inverted T-shaped hypapophyses of large size. They join each 

 other beneath to a greater or less degree in many of the genera. This 

 union more frequently takes place between the first and second, and the 

 first is always upturned and flanged out laterally, a feature prominently 

 reproduced in .Lagopas and Bonasa. These winglike side extensions of 

 the lower margins of the hypapophyses not infrequently are continued 

 on two or three consecutive ones, and are sometimes the widest on the 

 second. — Tetrao. 



Both in the Grouse and Partridges we find a free vertebra inserted 

 between the comjjound bone we have just been discussing and the first 

 sacral vertebra. This segment we must consider as belonging to the 

 dorsal series, although in Ciipidonia and Pedicecetes the upper and distal 

 aspects of its diapophyses are more or less moulded to conform with the 

 ilia. This bone is also figured in Plate YI, Fig 55, in conjunction with 

 the other dorsals, with which it has all its characteristics in common, 

 and such ones superadded as we might expect to find in a vertebra 

 naturally disjointed in the middle of the column. It has the longest 

 diapophyses of any of the series to which it belongs ; fiicets tor the 

 tubercula and capitula of its own free pleurapophyses ; a hypapophysis 

 of no mean length that may or may not be expanded below. 



Metapophysial spiculse on its transverse processes sometimes are so 

 far produced as to reach vertebme before and behind it. 



This segment is likewise imeumatic. 



There is a wonderful vein of regularity running through the dorsal 

 pleurapophyses, haemapophjses, and htemal spine or sternum. As to 

 the first pleurapophysis, or rather the first pair of these bones, we have 

 already described them as they are found in the ultimate cervical. 

 There we are aware it never reaches the sternum by the intervention of 

 a sternal rib ; that they are usually found to possess thoroughly devel- 

 oped heads and tubercles for the vertebra, their shafts being less flat- 

 tened than the dorsal ribs, and ouly in Lagojms did we discover any epi- 

 pleural appendages. 



As far as our observations extend, the consolidated jiortion of the 

 column of the dorsum has always consisted of four vertebra?, and con- 

 sequently we find in this portion four pairs of movable dorsal ploura- 

 pophj'ses and one pair for the free dorsal vertebra, reckoning five alto- 

 gether for this region. The first pair of dorsal vertebral ribs terminate 

 in free extremities, which are usually in line with the inter-ha^ma-pleura- 

 pophysial articulations in old specimens, and as a rule support epi-pleural 

 appendages, characteristic of the species to which the rib belongs. 



