180 Annals of the Carnegie Museum. 



This is precisely what 1 find in examining the same vertebrae in the 

 neck of Ardea herodias. It can best be studied in the neck of a fresh 

 specimen from which the skin has been removed, with the skeleton of 

 the neck of another individual at hand for comparison. 



The skeleton of the neck in Nycticorax differs in many particulars 

 from that of Ardca : a number of these points only become evident 

 after carefiil comparison, and will not be taken up in detail here. 

 Others show a profound difference in organization, such as — the first 

 pair of free pleurapophyses occurring on the seventeenth vertebrae in- 

 stead of on the eighteenth as in Ardea; the third, fourth, fifth and 

 sixth vertebrae are not elongated as in Ardea. but show the simple 

 gradation in size down the cervical chain : finally, the inferior wall of 

 the carotid canal is open in the last four vertebrae through which it 

 passes, in Nycticorax, and only in the last in Ardea herodias. 



Returning to the nineteenth vertebra in the Great Blue Heron, we 

 find that it has a high quadrate neural crest or spine which interlocks 

 by a free joint with the one behind ; it sends down a pair of ribs that 

 articulate with the sternum through the intervention of a pair of costal 

 ribs. The metapophyses are short and stumpy, barely reaching be- 

 yond the transverse processes. The bone has no descending hyapo- 

 physis, though a line marks the longitudinal center of the centrum be- 

 low. This fades away gradually on the remaining vertebrae. A large 

 pneumatic foramen pierces the bone, on either side, behind the trans- 

 verse process, and the cavities to which they lead seem to occupy all 

 parts of the bone. 



In the next four vertebrae we see but little change ; they are all 

 free elements ; the neural spines do not decrease any in height, but 

 they become shorter from before, backwards, shortest of all in the 

 twenty-third or the last free vertel^ra, before we reach those united as 

 one bone in the pelvis. Through this "dorsal region" the neural 

 canal of a Heron is strikingly small, even small in proportion with 

 the size of the vertebra. The transverse processes are narrower antero- 

 posteriorly as we proceed backwards, but at the same time reach out 

 further from the side of the vertebra As we proceed towards the pel- 

 vis we note also that the facet for the head of the rib gradually ap- 

 proaches the anterior part of the centrum of each vertebra, but finally 

 does not cpiite reach the anterior margin of the side of the neural 

 canal in the ultimate segment. A line joins this facet in each case, 

 with the facet for the tubercle of the rib, which is at the outer pos- 



