368 DR. p. L. SCLATER ON BIRDS FROM MEXICO. [DeC. 9, 



had now sat upon them nearly ten weeks, was evidently suffering from 

 the effects of a fast of thirty -two weeks, and there appeared to be no 

 reasonable prospect of hatching the eggs, they were removed. On 

 examination, we found about five or six with the embryos partially 

 formed. In one of these the embryo was about 1 1 inches in length, 

 the scaling and markings were shown, the colour was partially 

 developed, and the animal was evidently nearly ready for exclusion. 

 But the greater number of eggs contained only fatty matter in a 

 state of decomposition, and bore no traces of having ever been im- 

 pregnated. 



A single egg removed from the mother fifteen days after incuba- 

 tion commenced, curiously enough, chanced to be a good one. The 

 embryo contained in this was alive when it was opened, and measured 

 about 6 inches in length. 



About a month after the eggs were removed, the snake, which had 

 been at first very restless, changed her skin, fed as usual, and has 

 since remained in good health. 



I think that the present case, taken in conjunction with that which 

 happened in 1841 at Paris, and that of the Indian Python, kindly 

 communicated to me by George O. Wray, Esq., and already noticed 

 at a previous Meeting of this Society*, lead to the conclusion that 

 it is the normal habit of these highly developed Ophidians, the 

 Pythones, to incubate their eggs much as in the superior class of 

 birds. But it would appear that the Boas of the New World do not 

 follow the same practice ; for Mr. Westerman informs me that the 

 female Boa constrictor, which bred in the Zoological Gardens of 

 Amsterdam in 1861, brought forth living young ones, though some 

 eggs were produced at the same time. 



6. On some Birds to be added to the Avi-fauna of 

 Mexico. By P. L. Sclater, M.A., Ph.D., F.R.S., Secre- 

 tary TO THE Society. 



(Plate XLVI.) 



In a small collection of Mexican birds sent to me for examination 

 by M. F. Parzudaki, of Paris, I recognize several species new to the 

 fauna of Mexico, and not mentioned in my former communications 

 to this Society on the subject of Mexican ornithology, and others re- 

 quiring some few remarks. These are — 



1. Dendrceca superciliosa (Bodd.), Baird, B. N. A. p. 289. 



This specimen differs from others in my collection from N. America 

 and Jamaica in having the whole supercilia anterior to the eye 

 bright yellow, like the breast. Yet it is obviously not in full plumage, 

 being dull brownish grey above, and with the black markings hardly 

 defined. Prof. Baird alludes (I. c.) to somewhat similar variations. 

 At first I could hardly persuade myself that it was not of a dfferent 

 species. 



See P. Z. S. 1862, p. 108. 



