STUDIES OP THE MACROCIIIRES. 



313 



Passerine pattern for the byoid arclies, and I litive elsewhere 

 figured them for that form *. 



The sclerotal plates of the aye are composed of separate little 

 pieces of bone in all of these birds of which we have been speaking ; 

 but in old specimens in some of the TifrannidcB. I have often 

 noticed their tendency to anchylose together, notably in the 

 genus Sayornis. 



Passeres usually have a small sesamoid bone at the augle of 

 the jaw. I have failed to find it in Ampelis, but would prefer 

 examining more specimens before positively announcing its 

 absence. It seems to be invariably present where indicated in 

 all of the higher Thrushes. 



23. Of the remainder of the Axial SJceleton. — It wnll be pro- 

 bably a very long time before a sufficient number of the vertebral 

 columns of existing birds have been examined, to ascertain with 

 certainty whether the vertebrae composing them are constant 

 for the several divisions and for the species. "When this has 

 been done, and the exact averages ascertained, the result will 

 be no doubt important in assisting to decide doubtful points 

 in classification 



The figures recorded in the subjoined Table have in every case 

 only been set dowai after carefully counting the segments tw^o 

 or three times. With respect to the number of vertebra) in 

 the consolidated sacrum of the pelvis, they are here counted 

 in the adult bird, and consequently must be taken cum grano 

 salts, though I believe them to be quite correct. 



I am inclined to think at present that the number of free 

 coccygeal vertebra? are liable to vary even in representatives 

 of the same species. 



This Table, of course, could easily have been made far more 

 extensive, but in that case would have overstepped the object at 

 present in view^ I trust, however, that those who at any time 

 may be engaged in examining the structure of birds will record 

 such data as I have attempted to do here, and only after the most 

 careful counting. To do this, reliance can be placed only upon 

 spirit specimens, or recently killed birds, where there has been 

 no possibility of any of the vertebrae having been lost. 



* Shufeldt, R. W., " Osteology of Lanius ludovicianus excubiforides" Bull. 

 U.S. Geol. and Geog. Surv. of the Territories, vol. vi. pp. 351-359, pi. xiv. 

 fig. 101. Also same plate and figure in the author's collected memoirs 

 ' Contributions to the Anatomy of Birds.' 



