190 THE ZOOLOGIST. 



first, both sides of the next three arches, and on the outside of 

 the fifth arch. Those on both sides of the second and third 

 arches are more numerous than those on the outside of the first 

 arch. All the gill-rakers fit alternately and closely, making a 

 good filter. There are no pharyngeal teeth, upper or lower, to 

 be seen or felt. The mucous lining at the back of the mouth is 

 covered with papillae. 



Eigenmannia virescens, another of the Gymnotidce from 

 British Guiana, has seven tubercle gill-rakers on the first cerato- 

 hypobranchial, with three on the epibranchial. Under a fairly 

 high-power microscope, hair-like bristles are seen protruding 

 from these tubercles ; they bend over at the extremity, looking 

 like small claws. There are no pharyngeal teeth, either upper 

 or lower, to be felt or seen. The mucous membrane at the back 

 of the mouth is seen to have a corrugated surface when it is 

 magnified. 



AsPREDINIDiE. 



Aspredo sicuephorus has seven upstanding but soft gill-rakers 

 on the first cerato-hypobranchial arch, with two on the epi- 

 branchial. Similar but more numerous ones are on both sides 

 of the second, third, and fourth arches, with shorter ones on the 

 outside of the fifth arch. The longest of the gill-rakers is about 

 one-third of the depth of the gill-lamina below it. A prominent 

 ovoid pad, standing well up, of mucous membrane, is on the 

 heads of the third and fourth epibranchials, but no teeth could 

 be seen or felt. Neither could any be found for the lower 

 pharyngeal teeth. 



Mugilid^:. 



The pharyngeal teeth described in this series of articles have 

 always been such as could be plainly seen or felt. It is a 

 debatable question whether the cilia-like processes on the 

 mucous surface of the upper pharyngeal bones — for instance, in 

 Mugil b?'aziliensis — are technically teeth or bristles ; as they are, 

 however, to be seen only when highly magnified and are not 

 palpable to the touch, the Mugilidce have been put into the 

 category of fishes not having pharyngeal teeth. The same 

 reason caused the inclusion of the two Gymnotids above 

 described, as also that of the Aspredo. The family of the 

 Mugilida provides many excellent fish for the table. 



