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 TRYGONID^E. 



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. y 1881, p. 386) they are by no means 

 uncommon off the mouth of the Thames. 



Sub-Class CYCLOSTOMATA. 

 Family PETROMYZONTID^. 

 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 



