ShUKKI.DT : OSTI'-.OLOOY OF TIIK H KKODIONKS. 173 



union has not taken place, as we find it in the pelicans, gannets, and 

 others, where the entire median surflice of the inner carina! plates 

 fuse to form one descending keel in the middle line. 



My specimen of the immature Yellow-Crowned Night-Heron, shows 

 this union to be of so firm a nature, that it would not surprise me in 

 the least to find in an old adult of this species that ])erfect union had 

 taken place between the parts of these inner keels of the palatines that 

 come in contact behind. There is an excellent figure of the base of 

 the posterior half of the skull of Aidea cinerea in Professor Huxlev's 

 memoir upon the classification of Birds in the Proceedings of the 

 Zoological Society for 1867, Fig. 19, page 437. 



Fjg. 6. The hyoid arches of Ardea herodias, viewed from above. Natural size, 

 by the author from the same specimen as other figures. 



It agrees in every detail with the skulls of other true Herons that I 

 have before me, or have examined elsewhere. The pterygoid of the 

 Blue Heron is a straight, stout bone, feebly crested upon its upper side, 

 while its inner aspect is grooved for its entire length. Both ends are 

 dilated, the anterior one to receive the palatine head of the correspond- 

 ing side ; the other to articulate with the quadrate. Above this latter 

 extremity a projection is developed, on the outer side of which is seen 

 a large pneumatic foramen, which is double in some s|)ecimens. This 

 bone is devoid of any sign of a process at the usual site where one 

 usually develops to meet the baso-pterygoid apophysis when the latter 

 is present. Other Herons have the pterygoids constructed in precisely 

 the same way. I fail, however, to find the pneumatic foramina in the 

 Night Herons in the same locality as described above for^. herodias, 

 but no doubt a larger series of specimens would show it, as the same 

 projection exists in the pterygoid. 



In the Blue Heron the basisphenoidal region is elongated and de- 

 velops a median keel which merges into the inferior surface of the 

 rostrum just beneath the pterygoidal heads. The Eustachian tubes are 

 guarded only by a thin over-arching lamella of bone. As in Sula and 



