196 Annat,s of thf. Carnrgie MusEU.\r. 



rower than in A. Jierodias. A greater number of inter-apo])hysial for- 

 amina pierce in double rows the middle area in this Heron ; these, 

 however, may be obliterated in older birds. 



Nycficorax also possesses a true heron's pelvis, and so far as this 

 bone is concerned the differences between it and the pelvis oi Ardea 

 herodias are of so trivial a nature as scarcely to be noticed on first 

 sight. The principal ones are these : in Nycficorax the gluteal ridges 

 and outer angles are not nearly so prominent ; a greater number of 

 inter-apophysial foramina exists upon the dorsal aspect ; the last ver- 

 tebra, the thirty-eighth of the spinal column, anchyloses with the 

 sacrum, although it projects entirely beyond the pelvis, this one cor- 

 responding to the first of the free coccygeal series in A. herodias ; the 

 hinder ends of the ischiaare cut squarely across and do not apparently 

 project beyond the ilia; and finally, the obturator foramen is more 

 nearly entire. 



I find seven freely articulated coccy^^eal vertehrc^ \x\. Ardea iierodias 

 and a pygostyle. A. caudidissima shows but six, and the pygostyle, 

 but it may be possible that one of these vertebrce has by some accident 

 been lost in my specimen. We saw above in Nycficorax, how, in that 

 Heron the first one of the series anchylosed with the pelvis, both by its 

 centrum and by the antero-external angles of its diapophyses. 



These seven vertebrce in the Great Blue Heron are non-pneumatic, 

 and all but the last three entirely devoid of hypopophyses, and it may 

 be absent on the first of these. 



The first five have broad flaring diapophyses, which are entirely 

 aborted in the last segment, and only barely apparent in the one that 

 precedes it. 



In caliber, the neural canal is larger than we would be led to expect 

 from the size of that tube as it appears in the last uro-sacral vertebra 

 of the pelvis. 



The neural spines are bifid and subcompressed, while the form of 

 the anterior and posterior articular surfaces of the centra are transverse 

 and flattened ellipses. 



Herons being birds with short, weak tails, composed of but a few 

 feathers, we naturally find a correspondingly feebly-developed pygo- 

 style. 



In Ardea this bone has projecting from its lower anterior angle a 

 process nearly as long as half the bone itself. It represents the hypo- 

 pophysis of the leading vertebra that was absorbed to form, with prob- 



