138 Mr. II. J. Carter on the 



his adult livery ; whilst the female does not assume the white 

 "breast &c. until after one or, perhaps, several moults. It is 

 generally supposed that most eagles in a wild state assume 

 their adult plumage after the third change; but, from the 

 com])arative rarity of specimens in the brown plumage, it is 

 possible that the female Nisaetus pennatus may assume the 

 adult livery at the first moult. 



With regard to the male, as I have said, there is little altera- 

 tion from the nestling-plumage beyond a gradual change to a 

 paler cream-colour on the abdomen and flanks, and a gradual 

 narrowing of the striations. These last, however, are by no 

 means a safe guide to the age of a specimen ; for some indi- 

 viduals of the same sex are less streaked than others. The 

 very lightest-coloured male in my series, and lighter also than 

 any breeding female, is pronounced to be a remarkably clean 

 young bird which has never moulted, by Col. Delme-Radcliffe, 

 who is probably the highest living authority upon raptorial 

 birds. 



I am not writing the history of the Booted Eagle, and it is 

 tlierefore unnecessary to say more upon the subject ; but the 

 fact of the plumage of the two sexes being different in the 

 nestling stage, and subsequently becoming the same, is, so 

 far as I am aware, unparalleled in any other raptorial bird ; 

 and I have consequently deemed it worthy of being placed on 

 record. 



Note. — lam well aware that nestlings oi. Archihuteo sancti- 

 johannis are subject to considerable variation ; but it has 

 never been shown that these variations are either sexual or 

 constant. 



XIX. — On the Striae of Foraminiferous Tests ; with Reply to 

 Criticism. By H. J. Carter, F.E.S. &c. 



Whoever has studied fossilized Nuramulites must have been 

 struck with the striated appearance which their sections present; 

 and hence it is very desirable to remember that this is of two- 

 fold origin, viz. arising partly from what may be termed minera- 

 logical, and partly from organic causes. 



Tlie mineralogical structure of the foraminiferous test con- 

 sists of laminaj cut perpendicularly by strife, which therefore 

 in a globular Nummulite may often be seen to run directly 

 and continuously from the circumference to the centre. The 

 lamina? represent the lines of deposit, and the strias the lines 



