NATURAL HISTORY OF SELBORNE. 103 



long feathers growing not from their uropygium, but all up their 

 backs. A range of short brown stiff feathers, about six inches 

 long, fixed in the uropygium, is the real tail, and serves as the 

 fulcrum to prop the train, which is long and top-heavy, when set 

 on end. When the train is up, nothing appears of the bird before 

 but its head and neck ; but this would not be the case were those 

 long feathers fixed only in the rump, as may be seen by the 

 turkey cock when in a strutting attitude. By a strong muscular 

 vibration these birds can make the shafts of their long feathers 

 clatter like the swords of a sword dancer ; they then trample very 

 quick with their feet, and run backwards towards the females. 



I should tell you that I have got an uncommon calculus 

 czgogropila, taken out of the stomach of a fat ox ; it is perfectly 

 round, and about the size of a large Seville orange ; such are, I 

 think, usually flat. 



LETTER XXXVI. 



Sept. 1771. 



DEAR SIR, The summer through I have seen but two of that 

 large species of bat which I call vespertilio altivolans, from its 

 manner of feeding high in the air ; I procured one of them, and 

 found it to be a male ; and made no doubt, as they accompanied 

 together, that the other was a female ; but, happening in an 

 evening or two to procure the other likewise, I was somewhat dis- 

 appointed, when it appeared to be also of the same sex. This 

 circumstance, and the great scarcity of this sort, at least in these 

 parts, occasions some suspicions in my niind whether it is really 

 a species, or whether it may not be the male part of the more 

 known species, one of which may supply many females ; as is 

 known to be the case in sheep and some other quadrupeds. But 

 this doubt can only be cleared by a farther examination, and 

 some attention to the sex, of more specimens : all that I know at 

 present is, that my two were amply furnished with U-s parts of 

 generation, much resembling those of a boar. 



