168 Annals of the Carnegie Museum. 



through a large foramen on its mesial aspect. Owing to the broad 

 frontals, the orbital roof is very complete, while its outer periphery is 

 sharp and thin. This roof is quite horizontal in Ardea, as we see it 

 in the Gannets, but it is inclined to be tilted up in the Night Herons, 

 and consequently not shielding the eye so completely from above. 



The ethmoid is an unusualh' thick and bulky bone ; it spreads out a 

 wide base for the frontals to rest upon, and its straight anterior upper 

 margin bounds the cranio-facial hinge posteriorly ; its anterior surface is 

 broad, bearing a delicate medial crest, continued upon it from the apex 

 of the rostrum. Its internal structure is cancellous, and air is un- 

 doubtedly admitted to permeate it throughout. At a point, on either 

 side, half way between the rostrum and the roof, it supports a feebly 

 developed wing, the lower spur of which meets the backward extend- 

 ing process of the lower and smaller portion of the lacrymal. Among 

 such birds as the Gannets and Pelicans the ethmoid becomes lamelli- 

 form again, and it is not nearly as thick diametrically in the Night 

 Herons as we find it in Ardea. 



The middle third of the rostrum of the Blue Heron is a smooth 

 cylindrical rod, which posteriorly is gradually projected from the 

 sphenoid to merge anteriorly into the ethmoid. The inter-orbital 

 septum is very incomplete, presenting one large vacuity, with which 

 the foramina for the optic nerves have united, together with the smaller 

 nervous foramina found in many birds on the outer side of the latter. 

 Above this interorbital vacuity we note that the olfactory foramen is 

 also very large, and the groove for the nerve leading forward from its 

 anterior apex is faintly double. In my specimen of Ardea candidissiwa 

 all these openings have merged into one immense aperture, permitting 

 a full view of the interior of the brain-case. This individual is not 

 fully matured, however, and such may not be the case in the adult Egret. 



This does not hold good in the skulls of adult specimens of this 

 Heron, for I find since writing the above paragraph, that the arrange- 

 ment of these foramina in the crania of specimens of A. candidissii)ia 

 in the collection of Mr. Lucas as well as in those of this species in the 

 U. S. National Museum, is quite as I have described it for his A. 

 herodias. My thanks are due to Mr. Lucas for his courtesy in placing 

 at my disposal the material to which I refer. From the same source I 

 have been enabled to compare skulls of Bolaurus lentiginosus, B. exilis, 

 Ardea occideiitalis, A. egretta, several of .-^. candidissima, A. virescens, 

 Nycticorax n. iubvii/s and N. violaceiis, besides a few skulls and 

 skeletons of Herons from foreign lands. 



