2G2 Mons. A. Milne-Edwards on the 



the Curlews and Ibises the curvature is less regular, and 

 betrays itself especially in the terminal portion. In Apteryx 

 the mandible is much straighter. The two branches, but little 

 separated from each other at the articular portion, unite at a 

 great distance from their extremity and coalesce intimately, so 

 as to give the whole terminal portion of the bill great firmness. 

 The lower surface exhibits no trace of the original separation of 

 the dentary bones. It is rounded, and presents no such groove 

 as that which occupies the median line in the Ibises, and of 

 which traces are still perceptible in Apteryx. The bony tissue 

 in this portion is extremely close and strong ; it is only pierced 

 by a few orifices, and presents nothing to be compared to the 

 sponginess (so to speak) of the tip of the bill in the Godwits, 

 the Woodcocks, the Curlews, Apteryx, and others — a structure 

 which relates to the number of nerves and vessels meeting in 

 this part, and to which these birds owe the exquisite sense of 

 touch, enabling them to seek the worms which are hidden in 

 the earth and mud. This fossil bill was evidently not adapted 

 for such a diet, for it terminates in a sharp and strong point. 

 Behind the posterior branches of the dentary there is a narrow 

 but somewhat long fissure, indicating the original separation of 

 the dentary from the angular and the surangular. The posi- 

 tion of this fissure, placed obhquely from above downwards and 

 from before backwards, furnishes us with some rather impor- 

 tant characters ; in fact, this fissure, which I have called the 

 " post- dentary orifice or fissure,^^ is wanting in certain families, 

 such as the diurnal birds of prey. In the Passeres, properly so 

 called, it exists, but presents a peculiar form, very distinct from 

 that which I have just mentioned; it resembles, indeed, an ovate 

 fenestra, while in our fossil it is a real cleft left between the 

 difi'erent bones above named. The Passeres which have the 

 bill much curved, such as Promerops, Xiphorhynchus, Falculia, 

 Dendrocolaptes, Fregilus and so forth, present in this respect 

 exactly the same characters as those with a straight bill. In 

 the Gallinacea very considerable variation may herein be no- 

 ticed : thus, while in Pavo the postdentary orifice is almost 

 entirely efi'aced, it is enormous in the Grouse, and especially in 

 Teirao iiro(jullus, where it is j)laeed forwards at a very great 



