314 DE. E. w. shufeldt's moephological 



Species, 



No. of ver- 



tebra3 before 

 reaching the 

 sacrum. 



First free 

 pair of ribs 

 occur on 

 the 



No. of ver- 

 tebra; in 

 sacrum of 

 pelvis. 



No. of ver- 

 tebrae in 



coccygeal 

 division, in- 

 cluding 

 pygostyle. 





18 



12th. 



10 



9 





18 



12th. 



12 



7 



Tyrannus verticalis 



19 



13th. 



10 



8 



Otocoris alxKstris 



18 



13th. 



11 



7 



0£ this kind o£ data I think the greatest reliance is to be 

 placed in tlie number of free vertebrae in the cervical + the 

 dorsal region, as shown in the first column, far more than tliat 

 shown in the three remaining columns. If we take immature 

 birds, however, chosen just at that point in their development 

 when we can count with certainty exactly how many of these 

 segments will enter into the pelvic sacrum, and exactly how 

 many will be appropriated by the pygostyle, then the total count 

 of all the vertebrse in the column, irrespective of its divisions, 

 will be of value. 



24. In both Ampelis and Hesperocichla five pairs of dorsal ribs 

 possess costal ribs that meet the sternum, and each of these 

 birds have a pair of ribs that spring from the first sacral ver- 

 tebra, which articulate below with a pair of " floating " costal 

 ribs. This condition also obtains in my specimen of Tyrannus 

 verticalis, but in this species there are onl}^ four pairs of 

 costal ribs that articulate vvitli the sternumc These " sacral 

 ribs " are without epipleural appendages, though these processes 

 are found freely articulated at their usual sites upon all of the 

 true vertebral ribs in tlie several birds just alluded to. 



25. It has been always a matter of some surj)rise to me that 

 the pelvis of a bird has not had that importance attached to it 

 among skeletal characters which has been so universally awarded 

 to the sternum. In many respects its form in some species is far 

 more distinctive of the bird to which it belongs than the ster- 

 num can be, and is consequently more reliable. Eor instance, the 

 sternum of Passerine birds varies but very little throughout the 

 group, and in many cases it would be very difficult to designate 

 the species by simply examiuiug the sternum alone ; moreover the 



