CLASS PISCES. 121
Raia clavata, Linn. Thornback.
This very common fish is found in more shallow water
than any other species of Skate. It is usually esteemed the
best of the family for the table.
Family TRYGONIDAE.
Genus TRYGON, Adanson.
Trygon pastinaca Cuv. Sting Ray, or Fire Flaire. Locally,
" Fierce Claw."
I have occasionally taken this fish when trawling in the
estuary of the Blackwater.
It is more frequently taken in the channels between the
sands, if I may judge from the number of needles, made from
the spines upon its tail, that I have seen in the possession of
fishermen, who use them for stringing flat-fish together
through the gills, for the convenience of carriage.
Dr. Day says (Zool., 1881, p. 386) they are by no means
uncommon off the mouth of the Thames.
Sub-Class CYCLOSTOMATA.
Family PETROMYZONTIDAE.
Genus Petromyzon, Artedi.
Petromyzon marinus, Linn. Sea Lamprey.
This is captured occasionally in the mouths of all our
rivers. I once saw a very fine one that had been taken in the
Colne, and I have recorded (Essex Nat., vol. v., p. 134) the
capture of another in the same river. I never knew anyone
here who tried to eat his capture, most inhabitants of Essex