THE SKELETON. 27 



throughout the vertebrate series. Numerous important characters are to be 

 met with at the base of a bird's skull. A small bone, the vomer, 

 may or may not be present, while the delicate palatines and pterygoids 

 take on many forms. Their relations to each, their articulations, and the 

 morphology, of the bones of the avian palate, — the maxillo-palatines, the 

 palatines and associated elements, — have, by Mr.^Huxley long ago been des- 

 cribed and their differences and agreements employed in taxonomy. The 

 vomer is a single median bone, while the [)alatines and pterygoids are paired. 

 The latter upon either side articulate with the quadrate, and anteriorly with the 

 corresponding palatine. In a bird, as in many other vertebrates, the "base 

 of the cranium" is the most solid part of all the skull. It is made up princi- 

 pally of the basisphenoid, the occipital segments, the basitemporal, and in 

 part some of the elements of the sphenoidal group. Chief among the features 

 at the base of the cranium is the large subcircular opening found there, — the 

 foramen magnum, — that transmits the spinal cord as it passes to the brain. 

 In the median line, on its anterior margin, we find a sessile, subhemispherical 

 process, which is ihe occij>ital condyle, and it articulates with the first cervical 

 vertebra (atlas) of the spinal column. In this character, as in so many others, 

 birds agree with reptiles, while in the class mammalia, to which man belongs, 

 there is a pair of occipital condyles, one upon either side of the foramen mag- 

 num. With but few exceptions, the lower jaw of a bird, or its mandihle, is 

 always in one solid piece in the adult, while in the growing chick or fledgling, 

 it is found to be composed of a number of pieces or separate bones. There 

 are fve of these. They are the dentary which articulates or anchyloses with 

 the fellow of the opposite side to form the symphysis at the distal end; the 

 splenial, the angular, the surangular, and finally the articular, which 

 forms the free posterior extremity fashioned to articulate with the quadrate 

 upon either side. Development of the jaw-bone takes place about Meckel's 

 cartilage or the meckelian rod, a structure that is absorbed in adult life. 

 Several of the characters of the lower mandible in birds are of classificatory 

 value, not so much in the ramus or vertical lateral part of the bone, as the 

 processes of the articular ends, more particularly the posterior articular pro- 

 cess that, when developed, protrudes from behind the articular cups of the 

 hinder free mandibular ends. 



In the VERTEBRAL COLUMN we find an unusually long, and flexible cer- 

 vical portion or division, composed of numerous free vertebrae. Sometimes, 

 indeed very frequently, the lower cervicals bear ribs, and in a few cases a 

 cervical vertebra may fuse with the first dorsal to form the compound verte- 

 bral piece of the rigid dorsal division of the column in some birds. Often, 

 however, the dorsals are free, though they never possess the freedom of move- 



