PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 9 



for liis positive knowledge of tlieir specific identity, could suppose that 

 a certain fiat platform-nest of one pair ; the deeply-hollowed nest, with 

 its remarkable border of chevaux de fris, of another; and, again, the 

 beautiful pensile nest, like a Yireo's, of a third, were all nests of this 

 same species acadicus. 



The differences in the color of the eggs identified as those of fari- 

 ventris are, i^erhaps, more unusual and remarkable, certainly to their 

 extent. Here are two well-identified sets, those from Halifax, of an 

 unspotted white ; another set, but slightly spotted ; then Mr. Board- 

 man's set, strongly marked, but very differently from the eggs belong- 

 ing to the two most recently identified nests. The eggs of hammondi 

 and ohscurus are plain white, and no record exists of any spotted ex- 

 ample of either. The same is almost equally true of yninimHS. In sixty- 

 one eggs, only two are found with even faint spots; but this exception 

 may show the possibility of there being more variations than we are 

 now aware of. Among the eggs of difficilis a single specimen occurs of 

 very nearly unspotted white. The same is true of one egg of E. jnmllus. 

 Among the eggs of E. traillU unspotted eggs are comparatively more 

 common. Among my eggs of E. acadicus there is also one very nearly 

 an unspotted white. So that these variations in nests and m color 

 of eggs cannot be received as necessarily conclusive as against such 

 positive identifications as those of Mr. Boardman's and Mr. Downes's 

 examples. 



If we take the product of the average length multiplied by its aver- 

 age breadth at the point of the largest diameter as a proximate test 

 of the relative size of the eggs of each species, we find the following 

 result : 



Acadicus 4144 



Obscurus 4015 



Traillii 3096 



riaviventris 3900 



Pusillus 3930 



Difficilis 3720 



Hammondi 3328 



Minimus - 3200 



Since the above was in type, Mr. Charles A. Allen of ^^icasio, Cali- 

 fornia, has furnished me with some very interesting and apposite notes 

 on the nidification of Enipidonax difficilis, demoniiinxtiug the remarkable 

 variations that may exist in regard to the position and structure of the 

 nests of one and the same species of biixls. After mentioning that he 

 has taken and identified some forty or fifty nests of this species, he adds: 

 '' I find E. difficilis breeding in all situations. Sometimes I find them 

 on the curled root of a tree on the banks of a stream or brook, not over 

 six inches above the water; again I find them in the jagged end of some 

 half-submerged log in mid-stream; again within the loose V»ark of a 

 tree, no matter what kind, nine or more feet up; again I find them in a 



