Shufki.di' : Osteology ok ihk Hkrodiones. K;:; 



narial apertures are seen from this view, but their true form can best be 

 described from a lateral aspect of the skull. 



Across the cranio-facial articulation there is seen a transverse, de- 

 pressed tract, some three or four millimeters wide, where mesially, the 

 remains of the naso-premaxillary suture is still observable in the adult. 

 This transverse tract is quite thin, and owing to the fact that the 

 ethmoid stops abruptly behind it, beneath, on a line with its posterior 

 boundary, it allows considerable niovement in the vertical plane of the 

 bill on the remainder of the skull. How free this is in life I cannot at 

 this moment say, as I have not a Blue Heron in the flesh before me. 

 This depression fixes the boundary very definitely between the frontal 

 and postero-superior region of the upper mandible, and were it not for 

 it, these two surfaces would be continuous, gradually merging into each 

 other, which in fact they almost appear to do. The frontal region 

 is broad between the superior margins of the orbits, faintly venated, 

 and depressed longitudinally in the middle line. 



In the skulls of Sula bassana and Pelecanits fiisciis, specimens of 

 which I have before me, this region is likewise very broad, but the 

 median depression does not exist, it being but faintly marked in the 

 parietal region in these birds. 



Upon upper view of the skull of this Heron, we may also see the 

 superior aspects of the long and large lacrymals. They fit closely to 

 the sides of the frontals, and anteriorly encroach upon the external 

 borders of each nasal. 



The posterior orbital margins are pierced by a few minute foramina 

 on either side, into which lead the larger venations coming from the 

 parietal eminences. These latter are quite strongly marked here as they 

 are in other Herons. Among the Pelicans and Gannets, however, 

 this region is not thus distinguished. Still more posteriorly on this 

 aspect we observe the very broad fossa on either side, known as the 

 " crotaphyte fossa." The anterior margin of these fossae passes 

 directly across the skull, being simply interrupted in the middle line by 

 a small triangular jog, with its apex directed backwards and continuous 

 with the median line dividing the fossa;. Laterally, these fossae pass 

 out between the sphenotic and squamosal processes, occupying the en- 

 tire space. Posteriorly they are bounded by the supra-occipital line, 

 and a muscular line, on either side, leading to the sciuamosal process. 



(Fig- !•) 



This description of the crotaphyte fossoe oi Ardea herodias, answers 



