90 COMPARISONS OF STRUCTURE IN ANDIALS, 



ensis,) and tlie bimaculated sucker, (Lepido- 

 gaster himaculatus,) there are two suckers, one 

 formed by a union of the two pectoral fins 

 descending to the under surface of the body ; 

 the second by the ventral fins, which are united 

 by a membrane below, forming a concave suck- 

 ing disc. These fishes readily adhere to rocks 

 or stones, and even to the hand when they are 

 seized, which they cling to pertinaciously. 



In the difierent species of remora, the fins 

 do not enter into the construction of a sucker ; 

 but a large sucking disc, formed by numerous 

 transverse cartilaginous plates, occupies the 

 whole of the upper surface of the tead. These 

 fish adhere to others of larger size, and often to 

 sharks, or the keels of vessels, and are thus 

 carried about without exertion. 



We may here notice the lampreys, in which 

 the mouth is circular, and armed with hard 

 tooth-like processes, while the lips, forming a 

 continuous circle, act the part of a powerful 

 sucker, as we see in the leech. These fishes 

 attach themselves by the mouth to rocks and 

 stones, and are thus enabled to resist tides or 

 currents. Of these fish there are both marine 

 and river species. 



" In reference to the respiratory apparatus 



