the Ophrdium barbatum. 443 
the fame point to the bafis of the pe&oral, to its extremity ; and 
in the like manner for the ventral', anal, and tail fins ; all 
which meafures I refer to the common term 40. Admitting 
then the dcrfal fin is diftant from the upper jaw as ten, I write 
as before LC : I>I :: 40 : 10, which 1 reduce, if I chufe fo* 
Le. : DI 20 : 5. 
I take the meafures in length only, and never in breadth or 
depth, becaufe fuch meafures, on many accounts, for inftance, 
from the quantity of fpawn, from that of food in the 
ventricle, &c. would be uncertain ; befides there are terms 
enough afforded by the fituation of the anus and the fins. 
I pay no regard to the meafure of the noftrils, of the eyes, 
&c. as thefe parts lie too near the extremity of the upper 
jaw to admit of a fufficient accuracy in their meafure. All 
thefe diftances are written in the fhortefi; manner poffible ; I 
therefore do not go into the inquiry what clafs of the l in- 
ntean fyftem the fifh defcribed may belong to ; or whether 
the anal fin is before or behind the region of the dorfal ; whe- 
ther the pedtoral are extended beyond the ventral ; or the tail 
is forked or not ; and many other particulars which could not 
be expreffed but by a very long dbfcription, tedious both to the 
writer aiid reader. 
To make an application of the proportional meafurements, 
I fuppofe a fifh, of a ipecies defcribed, to be in length 40 lines, 
and from the upper jaw to the anus 10 ; I take a fpecimen 
which- 1 fufpe£t to be of the fame fpecies, but which I wifh to 
determine with. certainty : the length of it is 20 lines ; then I 
fay 40 is to 10 as 20 is to another term, which I difcover by 
multiplying 20 by 10, and dividing the product by 40, which 
will produce 5, the number of the lines comprehended • be- 
tween the upper jaw and the anus, if the fifh be of the fpecies 
it 
