A.rt. IV.— Osteology of 8peotyto Cuniciilaria 

 var. Hypogaea. 



By R. W. Scliufcldt, Acting Assistant Surg^eon, U. S. Army. 



In the United States we liave but one species of Burrowing Owl, and 

 this is a variety only of the bird found in South America. Our bird 

 occurs on the prairies west of the Mississippi, notably in the villages of 

 species of marmot squirrels, the deserted burrows of which it occupies 

 for the purpose of nidification. Its behavior and habits are extremely 

 unique and interesting. Perhaps no species in the great order to which 

 it belongs have less limited power of flight, none so habitually congregate 

 together in certain localities and choose the open, treeless country as 

 their resort, and make their nests underground. So, in the study of 

 the bony framework of this bird we may expect to find it modified 

 to correspond with these habits, and presenting equal points of inter- 

 est. Without further remark, then, upon its natural history, we will 

 proceed to an examination of its skeleton. In enumerating and describ- 

 ing the separate bones, smaller sesamoids than the patellae and the 

 ossicula auditus (two of the latter bones being merely represented in 

 cartilage) will not be taken into consideration. The latter are more prop- 

 erly treated in the study of the organ of heariug. 



The skull. — As a general rule, it is only in the young of the Class Aves 

 that the many bones of the skull can be separated from one another ; 

 the majority of the primitive segments of ossification of the four ver- 

 tebrae that go to form this, the superior expansion of the vertebral col- 

 umn, being firmly anchylosed together, with their sutures completely 

 obliterated when the bird has attained maturity. This is eminently 

 the case in the adult skull of the species we have before us, so mncli so, 

 in fact, that, with the exception of certain bones that remain perma- 

 nently free during life, we will undertake to describe the skull only as ib 

 presents itself to us in tlie adult as a whole. In referring to certain 

 points for examination, then, in this part of the skeleton, we will have 

 to rely largelj^ upon the reader's familiarity with general anatomy, the 

 extent and position of the bones as they occur in the variously sliai)ed 

 heads of immature birds, and as to which of the two divisions of authro- 

 potomists and some comparative anatomists, " bones of the cranium " 

 and "bones of the face", they belong. The major part of the occip- 

 ital lies in the horizontal plane, only that i)ortion which originally con- 

 stitnted the superoccipital segment and tlic i)osterioi- tliird of the ex- 



