IGO 
COMMON STUKGEON. 
in tlie more prominent parts there is some approach to regu- 
larity, on the whole tliis may be even the least depended on. 
Not only do the diiFcrent varieties differ in this respect, hut 
the variation exists in the same individual; so that a cord, 
laid along the middle line from the top of the head to the 
snout, shall sometimes separate the sides into portions which 
do not answer to each other. 
With regard to the plates on the back, Linnaeus, in his 
specific character of this fish assigns to it a row of eleven 
plates along the dorsal ridge; whereas Willoughby tells us 
that he had counted from eleven to tliirteen in several different 
examples; and particularly he mentions that behind the single 
dorsal fin there were no dorsal plates, where in most figures 
they are represented; and in the specimen presently to be 
described this portion of the body was ornamented and de- 
fended by a pair of parallel rows. Several other variations of 
figure might be brought forward, but I judge sufficient has been 
said to shew that the division of this well-known Common 
Sturgeon into two species has a less certain foundation in 
nature than has been supposed. 
Our description of this fish is taken from an example kindly 
presented by WiUiam Thompson, Esq., of Weymouth, whose 
desire to extend the boundaries of science has shewn itself 
in sim‘''ar instances on many former occasions. In this instance 
the obligation is so much the greater that it has enabled me 
with more ease, and at longer intervals, to examine the 
minuter particulars of form and structure, than if I had been 
limited to an inspection of what was exhibited in the boat of 
a fisherman, or a fishmonger’s shop. 
The example described measured three feet seven inches in 
length. The head at top is depressed into a wide channel, 
with the ridges on the sides more prominent; it slopes gradually 
to the snout, which becomes almost sharp at the end, where 
it is slightly bent up. This surface, and also the sides of the 
face are formed of a bony crust which is divided into sections; 
but when first from the water these divisions can scarcely be 
made out, and it is only when the suj-face has become 
dry that those plates can be distinguished, which have been 
represented in drawings of those parts. An elevated prominence 
stands before each eye. The plates arc more numerous, smaller, 
