the Ophidium barbafum.. 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 ; alb 
which meafures 1 refer to the common term 40. Admitting 
then the dbrfai fin' is diftant from the upper jaw as ten, I write 
as before JLC : DI :: 40 : 10, which 1 reduce, if I chufe fo„ 
3 Lc. : DI :: 20 : 5. 
I take the meafures in length only, and never in breadth or 
depth, becaufe fuch meafures, 011 many accounts, for infbmce, 
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. 
1 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 lin- 
n^an fyftem the fifh defcribed may belong to ; or whether 
the anal fin is before or behind the region of the dorfal ; whe- 
ther the pedoral are extended beyond the ventral; or the tail 
is forked or not; and many other particulars which could not 
be exprefTed but by a very long defcription, tedious both to the: 
writer and' reader. 
To make an application of the proportional meafurements, 
I fuppofe a fifh, of a fpecies defcribed, to be in length 40 lines,, 
and from the upper jaw to the anus 10 ; I take a fpecimen 
which I fufped 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 produd 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: 
