igo.'^] OSBORN CORRERPONDENCE. 227 



3^, depth inside i inch, outside i 3/8 inches. Mr. Frazer had seen 

 the bird, previous to g^etting- the nest and by comparison with a 

 cut of the bird in an ornithology, was certain of the identity. The 

 eggs measure ^ x f ^ inches, are thickly and evenly speckled 

 gray and yellowish gray on a 'ight brownish ashv background. 

 Two of the eggs have a decidedly plain band of slaty color about 

 the large end The following note was taken May 26, 1S98. 



At Mouth Keswick a pair of larks were found on ihe rond ; 

 two different times as the team neared the birds the female flew to 

 the fen e, while the malr would lower its wings, erect its crests, 

 spread its tail and with the middle feathers erected morethan those 

 of the sides which were at an angle of about twenty degrees, as if 

 in an attitude of defiance, an 1 it of sufficient size he would abolish 

 horses and outfit. He would hold his position, then with quick 

 flappings'of the wings and lerky flight would move on ahead a 

 short distance. 



July 9, 189S, an adult lark was observed feeding two young. 



CORRESPONDENCE. 



On the Age of the Belly River Series or Formation 



IN Canada. 



Editor ot the Ottawa Naturalist : 



The recent communication by Dr. H. M. Ami is very timely. 

 In conference with Mr. J. B Hatcher a somewhat similar point 

 has been raised, that the Belly River and the older formations in 

 Montana of somewhat similar age should be placed in the Upper 

 Cretaceous rather than in Mid-Cretaceous, This is largely a ques- 

 tion of the use of terms. In most geological text books the Creta- 

 ceous is divided broadly into Upper and Lower. In this sense the 

 Belly River falls in the upper division ; the Lower Cretaceous would 

 embrace the Kootanie stage ot the northern interior. In another 

 sense, and according to the usage which is shortly to be adopted 

 by the United States Geological Survey, the Cretaceous is to be 

 divided into Lower, Middle and Upper ; the Lower including the 

 basal, the Upper including the superior members of the series, and 



