] 78 A'NNALS OF THE CaRNEGIE MuSEUM. 



of 5.8 cm., while the epibranchials rarely exceed a centimetre and 

 a-half in length, are very slight, and have their hinder ends prolonged 

 by needle-like tips of cartilage, a condition vi^hich also obtains with 

 the end of the second basibranchial or urohyal. 



A specimen of the Snowy Egret before me has the bony parts of the 

 ear so well preserved that I am enabled to see the elliptical stapedial 

 plate, and the delicate bony rod of the mediostapedial part of the ap- 

 paratus. The sclerotal plates of the eye are elongated and rather nar- 

 row, they average from thirteen to sixteen in Ardea herodlas. 



Before entering upon the remainder of the axial skeleton, I will 

 take this 0[)portunity to further say that the tracheal rings also ossify 

 as in other birds. Comparatively, the tube seems to be of small cali- 

 bre, and I think one would rather be lead to look for a larger wind- 

 pipe in so big a bird. 



Of the Vertebral Column; Ribs. — (Figs. 25, 26, and 27.) In the 

 Great Blue Heron the atlas is not large, when taken in comparison 

 with the size attained by other vertebras in the column, as for in- 

 stance the nineteenth. Its cup for the condyle is notched above, 

 and on either side of the neural arch superiorly, the usual blunt processes 

 are thrown backwards (Fig. 25). 



The axis of this bird is a very irregular bone, and a difficult one to 

 describe without resorting to tedious detail. For this reason I have 

 added to my illustrations a figure presenting the appearance of this bone 

 on direct lateral view. It will be seen that the "odontoid process" 

 is quite large, being perfectly flat above and convex below. The cen- 

 trum is deep ; thinned in its center by the lateral concavities, beneath 

 which, its lower margin is carried by a gentle curve from the articular 

 surface at one end to the articular surfece of the other. An elongated 

 neural crest adds another curvature to the bone above. The facets of 

 the post-zygapophyses face directly downwards, and the entire bone is 

 much compressed from side to side. From the third to the sixth, the 

 vertebrte are much elongated ; their general pattern being seen on side 

 view in Fig. 27. Along the median line of their neural arches above, 

 these bones are thin and sharp. Their several articular facets are so 

 arranged that they only permit the head to be bent forward and back 

 again. 



The neural canal in them is small and circular on section. The 

 " vertebral canal " is present in all, being longest in the third verte- 

 brae and shortest in the sixth ; owing to the manner in which the 



